Year 2009 UCD-ITS-RR-09-21 

2007 Alternative Fuels Incentive Program (AFIP)

Plug-In Hybrid Electric Vehicle (PHEV) 

Demonstration and Consumer Education, Outread, and 

Market Research Program 

Principal Investigator: Kenneth S. Kurani 

Project Management: Kevin Nesbitt, Marilyn Kempster 

Researchers: Jonn Axsen, Nicolette Caperello, Jamie Davies, Tai Stillwater 

Plug-in Hybrid Electric Vehicle Research Center 

Institute of Transportation Studies 

University of California, Davis 

June 30, 2009 

Conducted under a grant by the California Air Resources Board of the 

California 

Environmental Protection Agency 

Grant Number: G06-AF04

Institute of Transportation Studies ◦ University of California, Davis 

One Shields Avenue ◦ Davis, California 95616 

PHONE: (530) 752-6548 ◦ FAX: (530) 752-6572 

WEB: http://www.its.ucdavis.edu
 i 

DISCLAIMER

The statements and conclusions in this report are those of the Grantee and not necessarily 

those of the California Air Resources Board or the University of California. The mention 

of commercial products, their source, or their use in connection with material reported 

herein is not to be construed as actual or implied endorsement of such products. 
 ii 

ACKNOWLEDGEMENTS

This work was funded through the California Air Resource Board’s Alternative Fuels 

Implementation Program (AFIP). Additional funding was provided by the California 

Energy Commission’s Public Interest Energy Research (PIER) Program. AAA Northern 

California, Nevada & Utah and Idaho National Laboratory (United States Department of 

Energy) provided in-kind support. 

We’d like to thank the thirty-four households who participated in the research reported 

here, especially inviting us into their homes multiple times, their willingness to complete 

questionnaires and interviews, and their frank evaluations. 
 iii 

TABLE OF CONTENTS

DISCLAIMER i

ACKNOWLEDGEMENTS ii

LIST OF FIGURES viii

LIST OF TABLES xi

ABSTRACT xii

EXECUTIVE SUMMARY I

Project Design I

1) HEV to PHEV Conversions I

2) Demonstration and Research II

3) Public Education and Outreach II

Research Activities within the Project II

A. Household response to the PHEV-conversions II

B. Narratives III

C. Interfaces and Instrumentation III

D. Social Influence IV

Participating Households IV

What PHEVs do Project Participants Design? V

Charging and Refueling Behaviors VI

Variation in Vehicle Use, Recharging, and CD-miles Across Households VIII

The Overall Effects of Recharging on Energy Use IX

Narrative Analysis: What, why and how? XI

Interfaces and Instrumentation XII

Social Influence on the Evaluation of, and Spread of Information about, PHEVs XIII
 iv 

1. A RESEARCH AGENDA TO ADDRESS HOW CONSUMERS DRIVE, RECHARGE, AND 

VALUE PLUG-IN HYBRID ELECTRIC VEHICLES 1

The Project in Context 2

Reasons for this Project 3

Are Consumers Impediments to PHEV Commercialization and Benefits? 3

Project Design Summary Description 5

1) HEV to PHEV Conversions 5

2) Demonstration and Research 6

3) Public Education and Outreach 7

Research Questions to be addressed in this Project 7

Research Activities within the Project 8

Household response to the PHEV-conversions 8

Narratives 8

Interfaces and Instrumentation 9

Social Influence 10

Defining Terms 11

Basic PHEV Design Concepts 11

2. PHEV DEMONSTRATION AND RESEARCH PLAN 15

Household PHEV Placements 15

Sampling 16

The Interviews and Questionnaires 17

Who are the Project Participants? 24

Gasoline Prices Faced by Survey Respondents and Demonstration Participants 27

Motivations and Knowledge regarding Electric-drive 28

3A. PROJECT RESULTS: PHEV DESIGNS 30

Whose PHEVs? Plausible early markets 30

What PHEVs do they Design? 31

PHEV Design Conclusions 39
 v 

3B. PROJECT RESULTS: RECHARGING 41

How often do People Plug-in their PHEV-conversions? 42

Electricity Availability And Instantaneous Power Demand 45

Electricity Availability & Instantaneous Power Demand: All Weekdays 46

Electricity Availability & Instantaneous Power Demand: Weekend Days 49

Variation in Vehicle Use, Recharging, and CD-miles Across Households 52

The Kermodes 55

The Overall Effects of Recharging on Energy Use 59

Recharging Conclusions 65

3C. PROJECT RESULTS: NARRATIVES 67

Narrative Analysis: What, why and how? 67

What is a Narrative? 67

The Value of Narratives 69

How do We Create Household Narratives? 70

Illustrative Stories from Three Households 71

The Lakes 71

Nancy 74

Octavia 75

Themes from Households’ Narratives 76

Changing Driving Behavior 77

Recharging Habits and Etiquette 78

Confusion 80

Payback 81

Narrative Conclusions 82

3D. PROJECT RESULTS: INTERFACES AND INSTRUMENTATION 84

Interface Details 84

Interface Themes from Household Interviews 90

Limited use of Web Resources 90

Abstract Information 91

Confusion 91
 vi 

Novelty 92

Learning from Interfaces 93

Gender Differences 94

Goal Setting 94

Impact of Additional Summary information on Fuel Economy 94

Michael and Cindy Mackson (5203) 96

Rick and Samantha Lake (6201) 97

Information Interface Conclusions 99

3E. PROJECT RESULTS: SOCIAL INFLUENCE 101

Background 101

Methods: Observing Interpersonal Influence 103

Stage 1: Contact primary household and elicit personal network. 105

Stage 2: Collect baseline information from the personal network. 106

Stage 3: Stimulate personal network with PHEV trial. 106

Stage 4: Network questionnaire and selected interviews. 107

Some Preliminary Results 107

The Noels as electric-drive novices 109

Billy Woods as an electric drive novice with an EV enthusiast in his network 111

The McAdams as pro-societal technology enthusiasts 111

The Rhodes as pro-societal technology enthusiasts with family values 112

Preliminary Discussion and Conclusions 112

4. DISCUSSION AND CONCLUSIONS 118

Putting Discussion and Conclusions in Context 118

Assessing PHEV Purchase Intentions and Design Priorities 120

It (still) isn’t about all-electric driving; it’s about fuel economy 120

Project results do differ from survey results in some important ways 121

If it’s not about all-electric driving now, can it be in the future? 122

Charging and refueling behaviors 123

Recharging: How often, where, and when 123
 vii 

Total Energy, with and without recharging 125

Recharging Habits and Etiquette: Infrastructure isn’t the only barrier 126

No One Misses Refueling with Gasoline 127

Driving behaviors 128

Summary Measures of Driving and Recharging 128

Changing Driving Behaviors through User Interfaces 129

Narrative Themes: Confusion and Payback 130

Confusion 130

Valuing PHEVs: Payback and Intuition 131

Social Influence 131

Five Approaches to Describing Social Interactions 132

Looking Forward 134

REFERENCES 135

ACRONYMS AND GLOSSARY 140

APPENDICES 142

APPENDIX A: HOUSEHOLD FINAL INTERVIEW PROTOCOL 143

APPENDIX B: PHEV BUYERS’ GUIDE (ON-LINE QUESTIONNAIRE) 147

APPENDIX C: PHEV DESIGN GAMES (ON-LINE QUESTIONNAIRE) 155

APPENDIX D: CALIFORNIA AND NORTHERN CALIFORNIA SURVEY OVERSAMPLES’

PHEV DESIGNS 155

APPENDIX E: PHEV PROJECT HOUSEHOLDS’ ELECTRICITY AVAILABILITY AND 

INSTANTANEOUS POWER DEMAND, DAILY 170

APPENDIX F: THREE PHEV PROJECT HOUSEHOLDS’ NARRATIVES 178

1. Rick and Samantha Lake 178

2. Nancy 189

3. Octavia 197
 viii 

LIST OF FIGURES

Figure ES-1: Electricity Availability (Percent of PHEVs Plugged-in) and Instantaneous 

Power Demand by Time-of-Day (Watts), Weekday Average. VII 

Figure ES-2: Gasoline-only Fuel Economy by Percentage of Miles Driven in CD Mode, 

Weighted by Total Monthly PHEV (CD+CS) Distance IX 

Figure ES-3: Decrease in Households’ Total Energy (Gasoline plus Electricity) for their 

PHEV-conversion (as compared to an HEV) by Percent of Miles driven in CD 

Mode, percent. XI 

Figure 1: Basic PHEV Drivetrain Options—Series vs. Parallel Design 12 

Figure 2: Illustration of Typical PHEV Discharge Cycle (65% DOD) 13 

Figure 3: Geographic distribution of PHEV Project participants (n=34) 17 

Figure 4: Screenshot of Development Priority game (Round Four) 22 

Figure 5: Screenshot of Purchase Design game (“high” price, vehicle model customized 

for respondent) 24 

Figure 6: Comparing gasoline prices from survey respondents (lines) and Project 

participants (diamonds) 27 

Figure 7: Comparing environmental beliefs among survey respondents (“CA” and 

“NCA”) and Project participants (“Demo”) 29 

Figure 8: Comparing electric-drive knowledge among survey respondents (CA and NCA) 

and Project participants (“Demo”): “From what you understand of these vehicle 

technologies, which can use fuel, and which can be plugged in?” 29 

Figure 9: Comparing base vehicles chosen for PHEV Purchase Design Game (plausible 

early market only: CA, n=286; NCA, n=63; Project, n=30) 32 
 ix 

Figure 10: Upgrades selected in PHEV design games by Project participants (plausible 

early market Project participants only, n=28) 33 

Figure 11: Distribution of selected PHEV designs in Round Four of Development game 

(plausible early market only: Project, n=28) 34 

Figure 12: Distribution of selected PHEV designs in high price scenario of Purchase 

Design Game (plausible early market Project participants only, n=30) 36 

Figure 13: Comparing upgrades selected in Round 4 of Development Priority game, 

(plausible early market only: CA, n=286; NCA, n=63; Project, n=28 36 

Figure 14: California Distribution of selected PHEV designs in Round Four of 

Development game (plausible early market only: CA, n=286) 37 

Figure 15: Northern California Distribution of selected PHEV designs in Round Four of 

Development game (plausible early market only: NCA, n=63) 38 

Figure 16: Three-Sample Comparison of upgrades selected in higher price scenario of 

Purchase Design game (plausible early market only: CA, n=286; NCA, n=63; 

Project, n=30) 38 

Figure 17: Mean Daily Household Recharging Frequency Distributions, Weekdays and 

Weekend Days, Percent 44 

Figure 18: Electricity Availability (Percent of PHEVs Plugged-in) and Instantaneous 

Power Demand by Time-of-Day (Watts), Weekday Average. 47 

Figure 19: Variability of Weekday Electricity Availability by Time of Day, Percent 47 

Figure 20: High and Low Weekday Instantaneous Power Demand, Watts 49 

Figure 21: Electricity Availability (Percent of PHEVs Plugged-in) and Instantaneous 

Power Demand by Time-of-Day (Watts), Weekend Day Average. 51 

Figure 22: High and Low Electricity Availability by Time of Day: All Weekend Days 51 
 x 

Figure 23: High and Low Weekend Days Instantaneous Power Demand, Watts 52 

Figure 24: Gasoline-only Fuel Economy by Percentage of Miles Driven in CD Mode, 

Weighted by Total Monthly PHEV (CD+CS) Distance 53 

Figure 25: The Kermodes’ Distance-weighted Gasoline-only Fuel Economy by 

Percentage of Miles Driven in CD Mode per Recharging Interval 56 

Figure 26: Improvement in Gasoline-only Fuel Economy from CS to CD operation, 

percent 60 

Figure 27: Decrease in Households’ Total Energy (Gasoline plus Electricity) for their 

PHEV-conversion (as compared to an HEV) by Percent of Miles driven in CD 

Mode, percent. 62 

Figure 28: Energy Monitor 85 

Figure 29: Consumption Monitor 86 

Figure 30: Entry Page 87 

Figure 31: Entry Page Energy Use Chart 88 

Figure 32: Entry Page Performance Comparison 88 

Figure 33: Entry Page Detail Table 89 

Figure 34: Trips Tab 89 

Figure 35 Change in fuel economy from without-access to with-access to the V2Green 

website (change is represented as the percentage change from the harmonic means 

of the first and second phases). 95 

Figure 36: Stimulating Social Networks with PHEVs 104 

Figure 37: Billy Woods’ Sociogram 108 
 xi 

LIST OF TABLES

Table 1: Upgrades for PHEV Development Priority game 21 

Table 2: Price of upgrades for Purchase Design game 23 

Table 3: Comparing Project participants, survey respondents, and the general population

26 

Table 4: Aggregate Measures of the Kermodes’ Actual and Constructed Months of PHEV 

Driving and Recharging 58 

Table 5: Energy Use and Savings, sorted by Percent Decrease in Total PHEV Energy Use

64 

Table 6: Conceptualization of PHEV attributes (hypothetical examples) 102 

Table 7: Summary of primary households and secondary participants in the personal 

network study to date 110 
 xii 

ABSTRACT

Will people recharge a vehicle that does not have to be recharged? This, and the degree to 

which plug-in hybrid electric vehicle (PHEV) designs emphasize gasoline or electricity, 

are central to assessing the energy and environmental effects of PHEVs. Plug-in 

conversions of hybrid vehicles are being made available to (predominately new-car 

buying) households throughout the Sacramento region for four to six weeks each. The 

vehicles are instrumented to report travel and energy; households are interviewed and 

surveyed. Results from the first 34 households—all selected in part because they can 

recharge a vehicle at home—indicate that on average they will recharge a PHEV about 

once per day, but with wide variation across households. The PHEV designs created by 

these households emphasize increased fuel economy rather than all-electric operation—as 

did the designs of prior representative samples of new-car buyers (who had not driven 

PHEVs). This result may be due in part to 1) “anchoring” (respondents are driving a 

PHEV that does not practically allow all-electric operation), and 2) households not 

creating integrated assessments of gasoline and electricity use/cost from the in-vehicle 

and internet-based instrumentation. Over the PHEV trials, narratives are co-authored 

about the PHEVs and their place in the ongoing life-stories of the participants. The 

primary themes to emerge are changing driving behavior, recharging habits and etiquette, 

confusion about PHEVs and how they work, and the role of payback analyses and more 

intuitive assessments of whether PHEVs are “worth it.” Tracing social interactions by the 

participants about the PHEVs reveals that complex translation of ideas and information 

about PHEVs is occurring as the PHEV drivers, in particular, use their trial period to 

reflexively explore lifestyle and identity possibilities of these new vehicles.
 I 

EXECUTIVE SUMMARY

This document reports on a research project designed to address the question, “Why 

would consumers buy plug-in hybrid electric vehicles (PHEVs)?” With funding from the 

California Air Resource Board’s Alternative Fuels Implementation Program (AFIP) and 

funding and in-kind support from other partners, the Plug-in Hybrid Electric Vehicle 

Research Center (PHEV Center) at the University of California, Davis implemented a 

PHEV Demonstration and Consumer Education, Outreach, and Market Research Project 

(hereafter referred to as the Project). This report describes the Project and summarizes the 

findings from the first thirty-four households. The Project will continue through 2009; 

results will be updated in subsequent reports. 

Project Design 

The Project was conducted as the following three main activities: 1) vehicle conversion 

to plug-in operation, 2) demonstration and research, and 3) education and outreach. 

1) HEV to PHEV Conversions 

Toyota Priuses were purchased and converted to plug-in operation using the Hymotion, 

(now, A123Systems) conversion package. A dozen such vehicles are regularly used in 

active support and conduct of the Project. The A123Systems conversion involves the 

installation of a 5KWh (nominal) lithium-ion battery in the spare tire well in the rear 

cargo area of the vehicle, as well as the necessary electrical and communications 

connections to incorporate the battery into the vehicle’s drive system and to recharge the 

battery. The battery charges from a standard US three-prong, grounded, 110-volt outlet. 

Using the PHEV terminology in this report, the PHEV-conversions used in this Project 

can be described as blended PHEV-30s, in which we adopt the definition of CD range as 

the distance at which the vehicle switches from CD to CS operation. This characterization 

will be restated in the discussion of the households to reflect their on-road performance in 

these vehicles. 
 II 

Additionally, the vehicles were equipped with onboard data collection and transmission 

devices. Idaho National Laboratory (INL) provided the devices and the cellular service to 

transmit the data. V2Green, Inc. (now, Gridpoint, Inc.) manufactured the data collection 

and transmission systems. They also summarize vehicle data on a website; UC Davis 

contracted for additional programming services to allow individual Project drivers to 

track their performance. 

2) Demonstration and Research 

The PHEV-conversions have been, and continue to be, placed in households in northern 

California for several weeks at a time. Households are recruited with the assistance of 

AAA Northern California, Nevada & Utah. During the households’ PHEV trial use 

periods, we collect data on travel, vehicle recharging and refueling, performance of the 

vehicle, and participants’ response to the PHEV technology. Data are collected directly 

from the vehicle using on-board data systems, as well as from interviews, questionnaires, 

and fueling logs.1

 

3) Public Education and Outreach 

The PHEVs were also used in a public education and outreach programs. The vehicles 

were displayed at public events and used in educational settings. Information on PHEVs 

remains accessible from the PHEV Center’s website. 

Research Activities within the Project 

Within the overall Project there are four related research activities. 

A. Household response to the PHEV-conversions 

In some sense the entire Project is about household response to PHEV-conversions. This 

specific activity focuses on the following results: 

 

1

 We can infer from vehicle data when it has been refueled with gasoline, but the only way to know how 

much was paid for gasoline is to have drivers record this information. 
 III 

1. What are the PHEV designs created by Project households and how do these 

designs compare to those created by survey respondents who have no experience 

driving PHEVs? 

2. What are the recharging behaviors of the Project households, and how do driving 

behaviors influence recharging behaviors? 

3. Given that Project participants are driving one specific incarnation of what a 

PHEV can be, what are the effects on their transportation energy use? 

B. Narratives 

We employ narrative research methods in this Project both to synthesize the large 

amounts of disparate data we are collecting for each household and to analyze both those 

synthesis documents and the original textual data from the household interviews. The 

purpose of the synthesis narratives is to tell the best possible story about each household 

and their experience with PHEVs. The purpose of subjecting the interviews to analysis is 

to ascertain what themes emerge across the households’ experiences. 

C. Interfaces and Instrumentation 

Research on driver feedback is carried out in two phases. First, we assess the participants’ 

use of and response to the in-vehicle energy information displays based on the stock 

Toyota Prius Energy Monitor and Fuel Consumption displays (as modified by the PHEVconversion) and the website displaying summary performance data from their vehicle. 

Results from this first phase of interface and instrumentation research are included in this 

report. 

The second phase of instrumentation research builds on the first, but is not scheduled to 

begin until summer 2009. In the second phase, a custom-made driver feedback display 

will be included as part of the research design for a subset of the Project households. 
 IV 

D. Social Influence 

A sub-group of 10 to 15 social networks (each centered on a household driving the 

PHEV-conversion) will be investigated to ascertain how interpersonal interactions 

influence assessment of electric-drive vehicles. Analysis of four networks has been 

completed to date and is discussed in this report. Three research questions are addressed: 

1. Do interpersonal interactions play a significant role in the assessment of electric 

drive vehicles? 

2. If so, how can we characterize the interpersonal interactions that influence 

consumer perceptions of functional, symbolic, and pro-societal attributes? 

3. Under what conditions might households adopt the pro-societal car? 

Participating Households 

Participants are recruited through an “illustrative” sampling method (Turrentine and 

Kurani, 2007.) Such a sample does not attempt to be representative of a population; 

rather, the purpose is to illuminate the behavior of specific groups. The sampling frame 

for the Project is defined by 1) automotive insurance requirements, 2) geographic 

location, 3) vehicle ownership, 4) driving behavior, and 5) broad categories of household 

structure. Participants are selected for the Project with the participation of AAA Northern 

California, Nevada & Utah. Volunteers from the recipients of the invitation letter log-on 

to a website hosted on a UC Davis server, where they complete a brief questionnaire 

which solicits more specifics of the potential participants vehicles, home, travel, 

household, and contact information. UC Davis researchers review the questionnaire 

responses and select households based on the goal to illustrate the responses of different 

types of households. 

In comparison to samples of the general population and of the population of California 

and northern California who have previously completed questionnaires for UC Davis 

regarding PHEVs (Axsen and Kurani, 2008), the Project households differ in that, on 

average, they have higher income, education, and likeliness to own their home. All three 
 V 

of these may be explained by a single design choice made for the Project: all participating 

households must have a place to recharge the vehicle at home. Still, the Project 

participants as a group only accentuate differences between our prior samples of new-car 

buying households and the general population; they do not introduce any new 

differences. In particular, the Project participants are similar to other recent samples of 

new car buyers in terms of concerns with environment and energy and knowledge about 

electric-drive vehicles. 

What PHEVs do Project Participants Design? 

At the end of their PHEV trial period, households complete a set of PHEV design 

games—the same design games completed by prior samples of survey respondents 

(Axsen and Kurani, 2008). The overarching conclusion from the design games is that 

even the Project households who have had a chance to drive a PHEV (that offers blended 

CD operation) do not design PHEVs that offer all-electric operation. Rather, the Project 

participants, like the survey respondents before them, create designs that emphasize 

improvements in (CD and CS) fuel economy. 

Project participants who had driven a (blended-operation) PHEV for a month were more 

likely than the previous survey respondents to 1) design a PHEV they are interested to 

buy rather than opt to buy a conventional vehicle, 2) design a PHEV that had better 

PHEV performance than the base PHEV design offered to them (the base offering took 

eight hours to recharge, achieved 75 mpg in blended CD operation for 10 miles, and 

achieved 10 mpg higher in CS operation than a conventional version of the same car), 

and 3) choose an HEV as the base vehicle they considered for redesign as a PHEV. The 

Project does appear to have a slightly greater persuasive effect in convincing participants 

that a PHEV is a worthwhile and desirable vehicle for their household. Still, these 

differences are at the margin, and the overall conclusions one draws from the Project 

participants are similar to those we drew from the survey. 
 VI 

Charging and Refueling Behaviors 

There may be no more fundamental question about PHEVs than whether or not people 

will plug-in a vehicle that does not have to be plugged-in. The answer from the Project 

participants to date is, “Yes, we will.” The Project households, on average, plugged-in 

these PHEV-conversions about once per day, and did so more often on weekdays than 

weekend days. There was large variation in the mean frequency of PHEV recharging 

across households—from zero to 2.6 times per weekday and zero to 1.5 times per 

weekend day. The mean frequency of plugging-in on weekend days was lower than on 

weekdays because there was now workplace charging and the PHEVs were more likely 

to be away from home, and thus away from the households’ primary or sole recharging 

location. Only a few households found away-from-home recharging locations they used 

on a regular basis. The incidence of zero charging on weekdays is largely explained by 

one household who decided that recharging the PHEV-conversion made too little 

difference to warrant their difficulty and hassle in recharging the vehicle. 

We assess the time-of-day distribution of PHEVs’ access to electricity and actual 

electricity demand to recharge PHEVs. The former is the distribution of times that 

PHEVs are plugged into the grid; the later is the distribution of times that electricity is 

actually being demanded by PHEVs for recharging. The weekday distributions from the 

last week of each of the 34 households are shown in Figure ES-1. 

Across the 170 weekdays represented in Figure ES-1 (34 households times 5 weekdays), 

70 percent of households had plugged in their PHEV between 10:00 pm and 6:00 am. By 

9:00 am only 20 percent of households had their PHEV connected to the grid. This can be 

explained by the number of respondents in the Project that have full time jobs, and 

typically leave home in the morning to go to work. While there were two households that 

charged during the day while at work, the PHEVs that were plugged-in to the electrical 

grid during midday were mostly due to retired individuals and teleworkers. At 4:00 pm, 

when households start to return home from work, vehicles begin to be plugged in, until 

10:00 pm by which time the percentage of households who have plugged in their PHEV 

stabilizes again at about 70 percent. 
 VII 

Figure ES-1: Electricity Availability (Percent of PHEVs Plugged-in) and 

Instantaneous Power Demand by Time-of-Day (Watts), Weekday Average. 

Given driving and recharging behavior by the Project households, electricity demand to 

recharge their vehicles ramps up at 5:00pm and peaks just after 10:00pm. It declines 

steadily through the rest of the night and into the morning, reaching practically zero by 

5:00am. While there were several households that charged during the day at work, most 

of the demand to recharge these vehicles was between 9:00am and noon. 

Weekend days differ from weekdays. Fewer PHEVs are plugged in during the weekend 

high availability period: about 55 percent of vehicles were plugged in between 11:00pm 

and 6:00am on weekends as compared to 70 percent between 10:00pm and 6:00am 

weekdays. The weekend high availability period starts an hour later than on weekdays. 

Compared to weekday recharging, it appears as though some individuals, if they had 

access to an outlet, plugged in longer during the weekend. However, on average, not as 

many people plugged in their vehicles on weekend days compared to average weekdays. 

As with weekday electricity demand, most actual weekend electricity demand to recharge 

the vehicles occurred between 5:00pm and 2:00am. There are significant differences in 

the total power required between weekdays and weekend days. On average, weekend 

electricity demand increased more slowly over the course of the evening. In general, this 
 VIII 

difference from weekdays is because during weekends the PHEVs are starting their 

recharging at a higher state of charge than on weekdays, and, thus, there is not as great a 

cumulative impact upon the power demanded. Essentially, as those vehicles plugged in 

later start recharging, their impact on the rate at which total power demand increases 

(summed across all households) is less than on weekdays, because other households’ 

vehicles which were plugged in earlier have already finished recharging. 

Variation in Vehicle Use, Recharging, and CD-miles Across Households 

The recharging results presented so far focus on the recharging behavior summed and 

averaged across the participants. This hides the variation in 1) the frequency with which 

people recharged the PHEV, 2) the distances households drive per recharging interval, 

i.e., the distance driven between two recharging events, and 3) the percentage of total 

miles each household drove in CD mode. The participants varied in their experiences 

with the vehicle, in their concepts and appreciation of the value of recharging, and in 

their access to different recharging locations. Figure ES-2 illustrates the overall 

variability in performance of the participants with regard to their average monthly 

(gasoline-only) fuel economy, the percentage of miles they drove in CD mode, and the 

overall distance they drove in the PHEV during their respective vehicle trials.2

In Figure ES-2, each circle represents one household. The diameters of the circles are 

proportional to the total miles driven by that household in the PHEV over their trial 

period. For scale, the largest circle (“Nancy,” in the lower left) represents just over 3,000 

miles of driving. That it also depicts the lowest percentage of miles in CD mode and 

nearly the worst gasoline-only fuel economy in the trial to date is due to several long, 

multi-day tours Nancy took away from home during which she drove the PHEVconversion many miles between recharging events. 

The basic conclusions to be drawn are that individuals varied greatly in their driving and 

recharging behaviors and, importantly, in the relationship between these two. A few 

households drove only 20 to 30 percent of their miles in CD mode. On the other hand, a 

 

2

 All household names are pseudonyms. 
 IX 

few households drove approximately 80 percent of their miles in CD mode and achieved 

monthly average gasoline-only fuel economy measures of approximately 70 mpg. 

Figure ES-2: Gasoline-only Fuel Economy by Percentage of Miles Driven in 

CD Mode, Weighted by Total Monthly PHEV (CD+CS) Distance 

Figure ES-2 shows the potential for drivers of these particular PHEV-conversions to 

achieve reductions in the gasoline-intensity of their daily mobility through differences in 

how they drive and recharge the vehicle, e.g., driving and recharging such that the miles 

in a recharging interval closely match the driver’s realized CD range. Still, there is 

tremendous variability in how closely participants’ behavior matches this technically 

ideal pattern that is not illustrated in Figure ES-2. 

The Overall Effects of Recharging on Energy Use 

First, we address changes in gasoline-only fuel economy because this was the primary 

metric used by households; we then turn to an analysis of the total energy effects. Across 

the group of households, mean CS fuel economy was 44.7mpg; mean CD fuel economy 

was 67.1mpg. Thus, the group mean increase in CD vs. CS is 49 percent. These group 

measures mask tremendous variation across households. The distribution of households’ 

mean fuel economy improvements between CS and CD operation ranged from 21 to 101 

0

20

40

60

80

100

0% 20% 40% 60% 80% 100%

Miles Driven in CD Mode, Percent

Kermode Lakes Nancy Octavia All other Households
 X 

percent. However, improvements over 70 percent were exceptions—90 percent of 

households had improvements less than 71 percent and the median improvement was 46 

percent. 

The analysis of total energy effects presented here is preliminary and partial. It is 

preliminary because we do not expect that the full range and variety of the relationships 

between travel and recharging behavior on one hand and total energy use on the other 

have yet been observed among the Project participants’ to date. Further, this analysis is 

preliminary because only one particular PHEV is analyzed. The analysis is partial 

because it is not a life-cycle analysis; here we address only electricity out of the battery 

and gasoline out of the tank. Further, the analysis is partial because we address only the 

marginal difference that it makes that the Project households drove and recharged (to the 

extent each did) a PHEV instead of an HEV. 

We compare their total energy use, i.e., gasoline plus electricity, during their PHEV trial 

to the amount of gasoline they would have used had they driven their entire PHEV trial 

without ever recharging. To illustrate relationships between driving, recharging, and 

energy use we plot the marginal percentage decrease in total gasoline (tank to wheels) 

plus electricity (battery to wheels) by the percent of their miles they drove in CD mode 

for their four-week PHEV trial in Figure ES-3. As in Figure ES-2, the size of each data 

point in Figure ES-3 is proportional to the total miles driven during each household’s 

trial. 

The first point is that a comparison of Figures ES-2 and ES-3 shows the households’ use 

of the simple measure of (gasoline-only) fuel economy is not qualitatively wrong. As the 

percent of miles driven in CD mode increases, fuel economy and energy savings both 

increase. Figure ES-3 confirms that across the households, energy was being saved 

through the substitution of electricity for gasoline by recharging the PHEVs compared to 

the amount of gasoline these households would have consumed had they not recharged 

the PHEVs. 

The relatively low percentage of CD driving of Nancy and the Kermodes—which we 

know was due to long, multi-day tours—yields low percentage energy savings from a 
 XI 

large (compared to the other households) base. Octavia and the Lakes achieved much 

higher percent energy reductions but across much less travel, and thus a smaller energy 

base. They did so in part because of the much higher percentage of their travel they 

accomplished in CD mode—accomplished both because they recharged more often and 

traveled fewer miles than Nancy and the Kermodes. 

Figure ES-3: Decrease in Households’ Total Energy (Gasoline plus 

Electricity) for their PHEV-conversion (as compared to an HEV) by Percent 

of Miles driven in CD Mode, percent. 

The range of percent total energy savings achieved by plugging in the PHEV-conversions 

in comparison to not plugging them in is from -1 to 19 percent. Higher percent savings 

are achieved by households who drive higher percentages of their miles in CD 

operation—either because they tend to drive fewer miles per day than their achieved CD 

range (and generally recharge everyday) or recharge multiple times per day. The 

household in which energy use increased was due to changes in drivers and trip distances. 

Narrative Analysis: What, why and how? 

We have two purposes in employing narrative: synthesis and analysis. First, we have a 

tremendous amount of disparate information about each household; narrative provides a 

framework to organize, analyze, and report all these data. Second, narratives explain, 

provide coherence, and show causality. 















   	 
 




 
 ! "# "$
%&$
 XII 

The primary themes to emerge from the narratives are changing driving behavior 

(primarily through the influence of the in-vehicle instrumentation), recharging habits and 

etiquette, confusion about PHEVs and how they work, and the role of payback analyses 

or more intuitive assessments of whether PHEVs are “worth it.” Some people changed 

how they drive the car after seeing their instantaneous fuel economy; others drove the 

PHEV as any other car, and specifically like they had no particular control over energy 

use. Some people likened plugging in the PHEV to recharging a cell phone and made it 

part of their daily routine, but were hesitant to recharge outside of their homes due to a 

lack in social etiquette and concerns for safety. Many people were confused about the 

state of charge of the battery; this influences how often they recharged. Some were 

concerned about the cost of the PHEV and payback; they saw PHEVs as helping with 

environmental problems but wondered how much they were paying to do so. 

Interfaces and Instrumentation 

There are two main sources of vehicle information available to study participants. First, 

there is the stock display console screen in the 2007 and 2008 model Toyota Priuses 

converted to PHEVs for the Project. The two screens are 1) an Energy Monitor schematic 

of energy flows in the vehicle as well as the instantaneous fuel economy, and 2) a 

Consumption screen that provides fuel economy averaged over 5-minute intervals and 

over the tank (or whenever the driver resets the average). 

Second, participants had access to the data they generated through driving, recharging, 

and refueling the vehicle via a website designed by the on-board data system provider. 

The website displays vehicle summary data as well as the location and status of the 

vehicle. Although the website provides detailed summary information—for example, 

driving data are summarized by trip, day, week, fortnight, and month—few participants 

reported being influenced by the website. 

The discussion of interfaces and feedback during interviews was subjected to additional 

analysis. The resulting themes were limited availability of web-based interfaces, 

information presented in abstract contexts, confusion (either about what certain 

information meant or about what behaviors to enact based on given information), novelty 
 XIII 

or lack of persistence of attention to information and new behaviors, learning, goal 

setting, and an hypothesis about gender-specific responses to energy information. The 

following lessons from these themes are proposed to guide further research into the role 

of interfaces and instrumentation: 

• The closer information is to the point of interest and action, i.e. in the car vs. on 

the home computer, the more likely it is that the information will be used. 

• Simplicity in representation and interpretation is critical to driver understanding. 

• The interface should support drivers in setting and achieving goals by providing 

relevant summary information. 

• Instantaneous Fuel Economy can provide drivers with erroneous information, 

especially during braking. 

• Whenever possible, information should be presented in a grounded context so that 

drivers can quickly understand the relative impact of their behavior. 

Social Influence on the Evaluation of, and Spread of Information about, 

PHEVs 

PHEVs and other electric-drive vehicles are innovations because of what they can do: 

new battery and drivetrain technology allows users to offset gasoline use with electricdrive capabilities and to plug-in to the electrical grid, often at home. From a functional 

perspective, consumers may interpret the desirability of electric-drive technology 

according to its ability to save them money on transportation, to improve drivetrain 

reliability, or to simply improve the experience of driving. But PHEVs, and electric-drive 

vehicles more generally, may also be assigned different social meanings than 

conventional vehicles. For example, Heffner et al. (2007) found five symbolized 

meanings that motivated HEV purchases: preserve the environment, oppose war, manage 

personal finances, reduce support to oil producers, and embrace new technology. Further, 

electric drive vehicles embody another class of attribute that differentiates them from 

conventional vehicles: the potential to benefit society in new ways. Green (1992, p133) 
 XIV 

provides a framework to classify goods on a private/public scale, where private good are 

characterized by “exclusive and personal consumption and individual payment; not 

associated with the public welfare,” whereas societal or public goods are characterized by 

“nonexclusive consumption and collective payment” such as “clean air” and “saving 

endangered species.” 

The first question in this social network research asks whether interpersonal influence 

plays a significant role in the assessment and adoption of electric-drive vehicles. The 

research reported here suggests that the observed social interactions are influential for 

primary households (those actually driving the PHEV-conversions) and secondary 

participants (members of primary households’ social networks who have volunteered for 

interviews). The second research question delves deeper to explore and characterize 

specific processes of social interaction and influence. We describe these interactions from 

five perspectives: contagion, conformity, dissemination, translation, and reflexivity. The 

primary households and their interaction with their social network illustrate (to some 

degree) each of these five approaches. We find the two most insightful approaches to be 

translation and reflexivity. 

Results to date suggest that interpersonal interactions within social networks play an 

important role in shaping the assessment of these PHEV conversions, and likely electricdrive vehicles more generally. Diffusion, conformity, and dissemination provide useful 

concepts for particular processes, but translation and reflexivity appear to best provide 

the language and theoretical depth required to integrate the various motives and 

perceptions observed among participating social networks. However, before conclusions 

can be drawn, more networks need to be explored and further analysis is required. 
 1 

1. A RESEARCH AGENDA TO ADDRESS HOW CONSUMERS DRIVE,

RECHARGE, AND VALUE PLUG-IN HYBRID ELECTRIC VEHICLES

This document reports on a research project designed to address the question, “Why 

would consumers buy plug-in hybrid electric vehicles (PHEVs)?” An integrated set of 

demonstration, research, education, and outreach activities was deployed to accomplish 

the following:

• Provide California households with the requisite knowledge and experience to 

provide informed responses to PHEVs, thus overcoming one primary impediment 

to commercialization—a lack of understanding by consumers, vehicle designers, 

fuels providers, and regulators of consumers response to the following: 

o Driving, recharging, and refueling patterns of PHEVs, that is, to what 

extent will drivers of PHEVs recharge from the grid or refuel the ICE, 

and where and when will recharging occur; 

o Different symbols of the meaningful and motivational features and 

capabilities of PHEVs, e.g., all-electric range, high fuel economy, 

electric-drive, ability to use renewable fuels, etc.; 

• Inform the California Air Resources Board of the potential effect of consumer 

driving and recharging/refueling behavior on the potential for PHEVs to reduce 

greenhouse gas and other vehicle emissions. 

• Inform the California Air Resources Board as well as the California Energy 

Commission, electric utilities, CalISO, and other parties of consumer response to 

PHEVs on the potential benefits, markets and impacts of PHEV technologies, 

including the following: 

o The potential for PHEVs to reduce petroleum consumption; 

o The effects of PHEVs on operation of the electrical grid; 

With substantial funding from the California Air Resource Board’s Alternative Fuels 

Implementation Program (AFIP) and additional support from the California Energy 
 2 

Commission’s Public Interest Energy Research (PIER) Program, the Plug-in Hybrid 

Electric Vehicle Research Center (PHEV Center) at the University of California, Davis 

implemented a PHEV Demonstration and Consumer Education, Outreach, and Market 

Research Project (hereafter referred to as the Project). Other Project contributors include 

the AAA Northern California, Nevada & Utah, and Idaho National Laboratory (United 

States Department of Energy). 

This report describes the Project and summarizes the findings from the first thirty-four 

households. The Project will continue through 2009; final results will be updated in 

subsequent reports. 

The Project in Context 

The Project is the third research activity in a multi-year, integrated research agenda. In 

brief, the agenda is as follows: 

1. PHEV “pioneers”—interviews of early converters of HEVs to PHEVs and drivers 

of these first conversions 

2. Internet-based survey of new car buyers’ baseline knowledge and priorities 

regarding PHEVs—samples representative nationally, with over-samples to 

represent new car buyers in California and northern California. 

3. Household PHEV Demonstration and Market Research 

a. Add improved in-vehicle energy feedback displays of cost, integrated 

feedback on electricity and gasoline use, emissions etc. 

4. A second large sample survey based on the prior PHEV research projects 

The first two research activities in this agenda are completed, the third is described in this 

report as are initial findings, and the fourth is forthcoming pending funding. As 

appropriate, the description and reporting of the design and results of the Project will be 

put into context of this larger agenda. For examples, some of the questionnaires 

completed by Project participants are the same as those completed by the participants in 
 3 

the prior national survey and the Project participants are compared to the northern 

California over-sample. 

Reasons for this Project 

This Project addressed the following questions: how will drivers use PHEVs—drive, 

recharge, and refuel them—and what kinds of PHEVs will buyers want? The defining 

feature of PHEVs—the ability to plug the vehicle into the electrical grid and refuel it 

from another network of liquid (or gaseous) fuels—is the source of both their potential 

benefits and the uncertainty over whether their potential can be realized. Much of the 

appeal of PHEVs is based on the flexibility afforded by two energy systems. This 

flexibility offers new choices for consumers, from a range of vehicle designs, e.g., size of 

battery and motor, as well as flexibility around the way the vehicle is used, e.g., how 

often the battery is recharged vs. how often the liquid (or gaseous) fuel is refueled. To 

achieve and optimize the potential of PHEVs to reduce vehicle emissions and gasoline 

consumption, i.e., to accomplish their societal benefits, PHEV owners will need to use 

electricity from the grid. 

Consumers will be faced with a previously unknown set of capabilities and thus 

unfamiliar choices. For example, the larger the battery chosen by buyers, the greater the 

percentage of their driving can be accomplished using electricity from the grid. On the 

other hand, the larger the battery the higher the initial price of the vehicle. As the initial 

vehicle price will be readily apparent, but the new and largely unfamiliar benefits only 

unfold in the future, sound policy and market actions depend on assessing potential 

consumers’ response to these distributions of costs and benefits. Moreover, PHEVs can 

be engineered to suit different consumers or regulators; PHEVs can be designed to 

minimize CO2 reduction, provide high torque and acceleration, maximize battery life, or 

maximize consumer control over the choice between electricity and gasoline. 

Are Consumers Impediments to PHEV Commercialization and Benefits? 

Are PHEVs to be encouraged because they represent a rich set of consumer and social 

values or discouraged as inviting unwelcome, unproductive tradeoffs between the here-
 4 

to-fore largely separate gasoline and electrical energy systems? One key variable in 

PHEV commercialization and in the attainment of any environmental and social benefits 

is the “locus of control,” that is, who has control over vehicle operations—drivers, 

vehicle engineers, or regulators? 

The fear of regulators, vehicle manufacturers, and energy suppliers is that drivers-incontrol could be deleterious to goals for the environment, air quality, energy 

consumption, energy systems operation, and the ability to warrant vehicles for emissions, 

fuel consumption, and reliability. In this worldview consumers are seen as at best 

disinterested and non-compliant, and at worst as anti-compliant. This bias is old and 

persistent; we believe it may be contradicted by a number of real world experiences. 

Writing a review of consumer energy research nearly three decades ago, McDougall et al

(1981) reveal such bias: “...recognize that probable energy savings represents a net 

impact based on potential savings in a technical sense, reduced to allow for imperfect 

behavioral response.” [Emphasis in the original.] More recently, Friedland et al. (2003) 

observe the continued absence of people in energy policy: “Especially lacking is policy 

or guidance that incorporates personal choices in energy–use reduction decision-making.” 

What this pessimistic view of people ignores is that at least some people if provided with 

control, information, incentive, and opportunity—such as can be provided with a 

PHEV—will exceed the “technical potential” possibilities. In interviews with buyers of 

non-plug-in HEVs, we have heard several accounts that suggest their drivers were saving 

more energy than technical analysts would calculate (Kurani and Turrentine, 2004; 

Heffner, Kurani, and Turrentine, 2005). This occurred by several means that illustrate the 

potential effects of driver control, information (feedback), incentive (symbolic and/or 

financial), and opportunity. In some cases, the HEV prompted further thinking by the 

owner about energy reductions in other areas of their life. Most directly (and in 

contradiction to economists’ assumptions of a rebound effect, i.e., increased driving 

because of reduced operating costs), some HEV drivers actively attempted to drive their 

HEV less than the vehicle it displaced. In gaming interviews with non-BEV owners we 

observed that when provided with an incentive in the form of a cost savings through the 

use of electricity rather than gasoline, these households appeared to quickly learn to 
 5 

adjust their travel between the use of a (hypothetical) BEV and their actual vehicles 

(Kurani and Turrentine; 1996, 2002). 

Project Design Summary Description 

This discussion points to two facts that guide the design of this Project. First, consumers 

are unaware of the potential advantages, disadvantages, new capabilities, and costs of 

PHEVs. Second, how consumers form their awareness, how they assimilate and process 

new knowledge about PHEVs, how they turn this awareness, knowledge, belief, and 

motivation into demand for PHEVs, and thus whether consumers will buy PHEVs, which 

type of PHEVs they would like to buy, and how they might drive, recharge and refuel 

those PHEVs are all largely unknown. 

The Project was conducted as the following three main activities. 

1) HEV to PHEV Conversions 

With funding from the California Air Resources Board, Toyota Priuses were purchased 

and converted to plug-in operation using the Hymotion, (now, A123Systems) conversion 

package. While such vehicle conversions are clearly only an interim step, they offer a 

test-bed for real world research with car-buyers. A dozen such vehicles are regularly used 

in active support and conduct of the Project. Another Prius (purchased with funding from 

the California Energy Commission) was converted, adorned with large signs identifying 

it as a PHEV and as a vehicle of UC Davis’ PHEV Research Center; this vehicle is 

reserved for education and outreach activities and support of the Project. 

The A123Systems conversion involves the installation of a 5KWh (nominal) lithium-ion 

battery in the spare tire well in the rear cargo area of the vehicle, as well as the necessary 

electrical and communications connections to incorporate the battery into the vehicle’s 

drive system and to recharge the battery. The battery charges from a standard US threeprong, grounded, 110-volt outlet. The recharging point is in the left-rear bumper of the 

vehicle. A fully discharged battery can be recharged in approximately five hours. 
 6 

It is important to understand that the converted vehicle remains subject to the underlying 

control strategy of the OEM vehicle. Specifically, these PHEV-conversions are best 

described as operating in a manner that more or less continuously blends electricity and 

gasoline—though it is the case that while the conversion, or supplemental, battery is 

discharging, far more electricity is being used than in a conventional Prius and it is easier, 

though by no means easy, to drive so that the ICE remains off. Still, even while the 

supplemental battery is contributing to the propulsion of the vehicle, aggressive 

accelerations, speeds higher than 35mpg, and upward grades are likely to cause the ICE 

to start to meet the additional load. 

Additionally, the vehicles were equipped with onboard data collection and transmission 

devices. The devices and the cellular service to transmit the data were provided to the 

Project by INL. V2Green, Inc. (now, Gridpoint, Inc.) manufactured the data collection 

and transmission systems. They also port the data to a website that summarizes vehicle 

performance. UC Davis contracted for additional programming services to allow 

individual Project drivers to track their performance. These information systems and 

modifications will be described further in section 3D: Instrumentation and Interfaces. 

2) Demonstration and Research 

The PHEV-conversions have been, and continue to be, placed in households in northern 

California for several weeks at a time. Households are recruited with the assistance of 

AAA Northern California, Nevada & Utah. The households are selected because they 

represent important markets segments and use patterns for PHEVs. The realized sample 

of Project participants to date will be described in detail in the next section. During the 

households’ PHEV trial use periods, we collect data on travel, vehicle recharging and 

refueling, performance of the vehicle, and participants’ response to the PHEV 

technology. Data are collected directly from the vehicle using on-board data systems, as 

well as from interviews, questionnaires, and fueling logs.3

 

 

3

 The demonstration vehicles are instrumented to record travel and recharging/refueling behavior. 

Additionally, drivers complete a refueling log: we can infer from vehicle data when it has been refueled 
 7 

3) Public Education and Outreach 

The PHEVs were also used in a public education and outreach programs. The vehicles 

were displayed at public events and used in educational settings. Information on PHEVs 

was accessible from the PHEV Center’s website. Education and outreach events included 

UC Davis’ Picnic Day and Whole Earth Festival, Earth Day activities, and other public 

events, school events, and vehicle displays. 

Research Questions to be addressed in this Project 

The Research and Education and Outreach activities address the following questions. 

• Purchase choices:

• What sorts of PHEV designs will buyers want? 

• Charging and refueling behaviors: 

• When, where and how much will PHEV owners choose to recharge from 

the electrical grid rather than refuel with liquid (or gaseous) fuels? 

• Driving behaviors: 

• When, where and how much of their driving will PHEV users accomplish 

by electricity vs. gasoline? 

• How does energy use and cost information affect driving and recharging 

behavior? 

• Broader impacts: 

• How will overall social and environmental benefits affect individual 

choices? 

• What information about PHEVs is spread through the social networks of 

participants and how do those exchanges affect the formation of drivers’ 

values regarding PHEVs? 

 with gasoline, but the only way to know how much was paid for gasoline is to have drivers record this 

information. 
 8 

Research Activities within the Project 

Within the overall Project there are four related research activities, these are briefly 

described here and more fully discussed in the following major sections of this report. 

Household response to the PHEV-conversions 

In some sense the entire Project is about household response to PHEV-conversions. This 

specific activity focuses on the following results: 

1. What are the PHEV designs created by Project households and how do these 

designs compare to those created by survey respondents who have no experience 

driving PHEVs? 

2. What are the recharging behaviors of the Project households, and how do driving 

behaviors influence recharging behaviors? 

3. Given that Project participants are driving one specific incarnation of what a 

PHEV can be, what are the effects on their transportation energy use? 

The other activities described next explore why the responses above are as they are, how 

they are formed, and how they might be influenced by information. 

Narratives 

We employ narrative research methods in this Project both to synthesize the large 

amounts of disparate data we are collecting for each household and to analyze both those 

synthesis documents and the original textual data from the household interviews. Each 

household completes three on-line questionnaires including two sets of complex PHEV 

design games. Each household completes three to five semi-structured interviews, 

resulting in two to six hours of recorded and transcribed conversations. Each vehicle is 

equipped with on-board data collection systems, resulting in 500,000 to 700,000 records 

on the household’s driving, recharging, and refueling of the vehicle. Synthesis narratives 

are written by incorporating data from all these sources. Narratives have beginnings and 

ends, but are more than simple chronologies of events; they have plots to give meaning 
 9 

and coherence to events. The starting point for synthesizing the data into a narrative 

begins with the interviews. Additional data are brought in from the questionnaires, e.g., 

the PHEV designs created in the on-line questionnaires. The interviews explain why the 

households designed the PHEV they did, supported (or contradicted, if that is the case) by 

the data from the vehicle. 

The purpose of the synthesis narratives is to tell the best possible story about each 

household and their experience with PHEVs. The purpose of subjecting the interviews to 

analysis is to ascertain whether themes emerge across the households. That is, what can 

we say about the groups’ experience? For example, across the group how do households 

talk about similar things, e.g., recharging? 

Both the synthesis narratives and the interview analyses are somewhat contrived since, in 

general, the entire Project is an intrusion into the participants’ ongoing lives (narratives) 

and specifically, the interviews are semi-directed and therefore not entirely of the 

households’ own telling. For example, knowing that recharging behavior is central to the 

research goals of the Project, all households are asked to talk about recharging. We 

neither simply wait to listen to whether they talk about recharging, nor allow them to 

complete their interview without at least addressing questions about recharging. 

Interfaces and Instrumentation 

Research on the effect of driver feedback is carried out in two phases. The first is integral 

to the design of the vehicles, PHEV-conversions, and on-board data systems deployed in 

this Project. The PHEV-conversion process adds a color change to the battery icon on the 

stock Prius Energy Monitor to tell the driver when the vehicle has switched from CD to 

CS operation.4

 The on-board data systems transmit data to the service provider, who 

displays summaries of the data on a website. As part of the household interviews, we 

assess the participants’ use of and response to these two interfaces. Further, we examine 

whether the addition of the website information makes any measurable impact on the 

 

4

 Terminology used to describe the operation of PHEVs is explained fully in the following sub-section: 

Defining Terms. 
 10 

vehicle performance as recorded by the on-board data systems. (Most of the households 

included in this report were not provided access to the website displaying their vehicle’s 

data until halfway through their trial month.) Results from this first phase of interface and 

instrumentation research are included in this report. 

The second phase of instrumentation research builds on the first, but is not scheduled to 

begin until summer 2009. In the second phase, a custom-made driver feedback display 

will be included as part of the research design for a subset of the Project households. The 

display device will allow the driver to choose from a variety of information to be 

displayed. Evaluation will be based on additional survey and interview questions as well 

as data recorded by the existing V2Green data systems and the new in-vehicle device. 

Social Influence 

Within this PHEV demonstration, a sub-group of 10 to 15 social networks (each centered 

on a household driving the PHEV-conversion) will be selected investigate how 

interpersonal interactions influence the assessment and adoption of electric-drive 

vehicles. Analysis of four networks has been completed to date and is discussed in this 

report. Three research questions are addressed: 

1. Do interpersonal interactions play a significant role in the assessment and 

adoption of electric drive vehicles? 

2. If so, how can we characterize the interpersonal interactions that influence 

consumer perceptions of functional, symbolic, and pro-societal attributes? 

3. Under what conditions might households adopt the pro-societal car? 

To explore these research questions, this project maps, measures, and stimulates the 

personal networks of selected households. A multi-method qualitative approach is 

followed, combining semi-structured interviews, internet-based questionnaires, and a 

social episode diary technique to track each social network. First, prior to receiving the 

PHEV, the participating household is asked to map their social network and invite several 

people from it to take part in the study. During each participant’s PHEV trial, information 
 11 

is collected regarding their social discussions and interactions with network members—

seeking to characterize how social interactions influence perceptions, expectations, and 

ultimately, purchase intention. Findings will help inform policymakers, researchers and 

industry how new technologies with pro-societal attributes could enter the market. 

Defining Terms 

In this section we present the basic vocabulary that we will use throughout this report to 

describe PHEVs. Some of this vocabulary is intended for readers of this report, i.e., it is 

not the vocabulary we necessarily used when we spoke with our participants about 

PHEVs. Describing where and how those two vocabularies diverge is one of the 

developing outcomes of the overall research agenda of which this Project is a part. 

A PHEV has both an electric motor and a heat engine—usually an internal combustion 

engine (ICE).5

 This flexibility also complicates vehicle designs and possible ways of 

using energy from two different systems. Figure 1 shows two simple schematics of 

possible PHEV architectures, i.e., the overall design of the PHEV system to supply power 

from two different sources. A series architecture powers the vehicle only by an electric 

motor using electricity from a battery. The battery is charged from an electrical outlet or 

by the gasoline engine via a generator. A parallel architecture adds a direct connection 

between the ICE and the wheels, adding the potential to power the vehicle by electricity 

and gasoline simultaneously and by gasoline only. As examples of each architecture, 

General Motors is working on a series architecture, e.g. the Chevy Volt and Toyota is 

developing a PHEV with a parallel architecture, e.g. a plug-in version of the Prius. 

Basic PHEV Design Concepts 

Here we explain four fundamental PHEV concepts that will frame our questions with 

participants throughout all phases of the PHEV research agenda and the Project in 

particular. First, for any given architecture, a PHEV can operate in one of two modes: 

charge sustaining (CS) or charge depleting (CD). Figure 2 (adapted from Kromer and 

 

5

 As the ICEs in most conventional light-duty vehicles in the US are fueled with gasoline, we will refer to 

gasoline and gasoline engines without precluding the possibility of other fuels. 
 12 

Heywood, 2007, p.31) illustrates these two modes. The vertical axis is the battery’s state 

of charge (SOC); the horizontal axis is the distance traveled. In practice, the maximum 

SOC may be limited to less than 100 percent, and the minimum SOC higher to more than 

0 percent, both to preserve battery life and improve safety. The difference between the 

maximum and minimum SOC is known as the usable depth of discharge (DOD), which 

varies across battery and vehicle designs. 

In the Figure 2 example, the battery is “fully” charged (from an electrical outlet) to 90 

percent SOC. Once it starts driving, the PHEV is driven in charge-depleting (CD) 

mode—energy stored in the battery is used to power the vehicle, gradually depleting the 

battery’s SOC. Once the battery is depleted to a minimum level, set at around 25 percent 

in this example, the vehicle switches to charge-sustaining (CS) mode. In CS mode the 

SOC is sustained by relying primarily on the gasoline engine to drive the vehicle, only 

using the battery and electric motor to increase the efficiency of the gasoline engine, as is 

now done in an HEV. The vehicle remains in CS mode until the battery is plugged in to 

the electric grid to recharge. The distance a fully charged PHEV can travel in CD mode 

before switching to CS mode is one definition of CD range. 

Figure 1: Basic PHEV Drivetrain Options—Series vs. Parallel Design 

ENGINE

MOTOR

GENERATOR

ELECTRICAL

OUTLET

GASOLINE

MOTOR

GEN.

ELECTRICAL

OUTLET

GASOLINE

Battery

ENGINE

Battery

Series Parallel
 13 

Second, a PHEV can be designed for all-electric or blended operation in CD mode. A 

PHEV designed for all-electric operation can be driven for the CD range using only 

electricity from the battery, and the engine is not used at all. In contrast, a PHEV 

designed for blended operation will use electricity and gasoline to power the vehicle 

throughout the CD range—energy from the engine and the battery are “blended” together 

through the electro-mechanical drivetrain. Thus, a PHEV designed for all-electric driving 

will require a battery capable of delivering more power than a PHEV designed for 

blended driving because the battery (and motor and power electronics) must be capable 

of providing the full power of the vehicle, not just partial power. 

Figure 2: Illustration of Typical PHEV Discharge Cycle (65% DOD) 

Source: Adapted from Kromer and Heywood (2007, p31). Used with permission from authors. 

Third, PHEV designs are commonly described according to CD range; the common 

notation is PHEV-X, where X is distance in miles. For instance, a PHEV-10 can be driven 

10 miles in CD mode before switching to CS mode. However, this notation does not 

Distance

Battery State of Charge (SOC)

Charge Sustaining (CS) Charge Depleting

(CD) Range

Gasoline

Only

All Electric (AE) or

Blended (B)
 14 

distinguish whether a PHEV in CD mode is operating all-electrically or by blending, nor 

does it specify the driving conditions that would allow CD mode for the stipulated 

distance. Comparisons of PHEVs, even those sharing the same PHEV-X designation, 

must reconcile assumptions regarding CD mode and driving behavior. 

Kurani, Heffner, and Turrentine (2007) discuss how further confusion in PHEV notation 

can result from two differing concepts of PHEV-X. First, Gondor and Simpson (2007) 

argue that X should be defined as the equivalent number of miles of petroleum displaced 

by electricity from the battery. This approach makes no distinction between all-electric

and blended operation; a fully charged PHEV-10 could store and use enough electricity 

to reduce gasoline use by the amount of gasoline required to travel 10 miles, but not 

necessarily during 10 continuous miles of all-electric operation. On the other hand, the 

California Air Resources Board (CARB, 2003) defines X as the total miles that can be 

driven before the gasoline engine turns on for the first time, also known as all-electric 

range (or zero-emissions range). By this definition, a fully charged PHEV-10 could be 

driven for the first 10 miles without using any gasoline. As of the writing of this report, 

CARB is considering a proposal to allow PHEVs designed for blended operation to 

receive credits under the zero emissions vehicle regulation (CARB, 2008b). 

Using the language developed in this section, the PHEV conversions used in this Project 

could be described as blended PHEV-30s, in which we adopt the definition of the 

distance at which the vehicle switches from CD to CS operation as the definition of CD 

range. We will return to this vehicle characterization in our conclusions, modifying it in 

accordance with the on-road performance of our first 34 households. 
 15 

2. PHEV DEMONSTRATION AND RESEARCH PLAN

The Project provides households with real-world experience with PHEVs prior to asking 

them to evaluate such vehicles and offer their preferred PHEV designs. 

Household PHEV Placements 

PHEV-conversions are placed in households for periods of time that allow for the 

household members to learn and adapt. Starting in late-August 2008, household 

placements were initially scheduled for four weeks. After completing the research 

process with over twenty households, we judged that four weeks was not long enough for 

many of the households. In particular, some were still learning about recharging and its 

effects on energy use and cost. Further, most households were still talking about the Prius

per se, leaving less time to discuss the added plug-in capability.6

Starting in February 2009, households in the Project use the vehicles for six weeks. The 

PHEV-conversion package allows for the conversion to be taken off-line, returning the 

operation of the vehicle to that of a conventional Prius.7

 Therefore, the PHEVconversions are now delivered to the households with the conversion off-line. The 

conversion is placed back on-line after two weeks. This allows the households to respond 

to a (more-or-less) conventional Prius and then move on to experience and evaluate a 

particular PHEV. Further, the two-week pre-PHEV period allows us to establish a 

baseline of driving performance based on data from the on-board data systems. 

Participants are interviewed at the start of, during, and at the end of their PHEV trial to 

make sure the vehicles are working properly and to explore with the household their use 

of and response to the vehicle. Further, the households complete a screening 

questionnaire (used in recruiting participants) and the first and third parts of the 

 

6

 Of the households included in this report, only one was a pre-existing HEV owner. Additional HEV 

owners are being included in the subsequent sample. 

7

 Because the conversion package adds weight, the Priuses in our demonstration—with the conversions offline—can be expected to return slightly worse fuel economy than unconverted Priuses. 
 16 

questionnaire previously administered to representative samples of the US, California, 

and the counties along the Interstate 80 corridor from the San Francisco Bay Area to 

eastern suburbs of the Sacramento region. The last region was over-sampled in particular 

to provide a comparative population for the households participating in the Project. 

Sampling 

Participants are recruited through an “illustrative” sampling method (Turrentine and 

Kurani, 2007.) Such a sample does not attempt to be representative of a population; 

rather, the purpose is to illuminate the behavior of specific groups. The sampling frame 

for the Project is defined by 1) automotive insurance requirements, 2) geographic 

location, 3) vehicle ownership, 4) driving, and 5) broad categories of household structure. 

Participants are selected for the Project in a three-stage process. First, AAA Northern 

California, Nevada & Utah issues an invitation to their automotive policyholders who 1) 

meet minimum requirements regarding the amount of insurance they carry and their 

driving records, and 2) live within the geographic region specified by researchers at UC 

Davis. Presently that region is roughly defined as the area within about 30 to 45 minutes 

driving time of Davis, CA. Second, volunteers from the recipients of the letter are 

instructed to log-on to a website hosted on a UC Davis server, where they complete a 

brief questionnaire which solicits more specifics of the potential participants vehicles, 

home, travel, household, and contact information. Third, researchers review the 

questionnaire responses and select households based on the goal to illustrate the 

responses of different types of households. 

An illustration of the interaction between Project management and research goals is the 

geographic distribution of the participant households summarized in this report as shown 

in Figure 3. To initially simplify the logistics of vehicle delivery, pickup, and household 

interviews the first participants were selected from the city of Davis, CA. However, an 

important research goal is to incorporate households in a variety of towns, cities, and land 

use settings within these towns and cities. As can be seen in the figure, this goal is being 

achieved and will be furthered as additional participants are selected during the remainder 

of the Project. 
 17 

Figure 3: Geographic distribution of PHEV Project participants (n=34) 

The realized Project sample-to-date will be compared to the California and northern 

California survey respondents after we describe the interviews and questionnaires from 

which the comparative data are taken. 

The Interviews and Questionnaires 

Each household was interviewed three to five times: upon vehicle delivery, every two 

weeks, and finally after the last week when the vehicle was retrieved. Interviews last 

between one and two hours. Two researchers attend the first and last interviews. All 

interviews are recorded; all but the first interview recordings are transcribed. The initial 

interviews tend to be given over to formally enrolling the household in the study—which 

must happen before the vehicle can be handed over and substantive interviewing can 

begin. During this first interview, researchers primarily listen for the questions the 

household has about the vehicle, offering answers that are as non-leading as possible. For 
 18 

example, every household asks how often the vehicle should be plugged in. Our standard 

response is that these cars can be driven without ever being plugged in, but that what we 

are hoping to learn from the household is how often they plug-in and why. 

The second and third interviews follow protocols, i.e., outlines of topic areas to be 

covered with every household. Each topic area includes example prompts that are not 

used in every household, but only as needed or appropriate to each household. An 

example of the protocol is included in Appendix A. 

In addition to the recruiting and screening questionnaire, each household in the Project 

also completed a two-part online survey eliciting several types of data. The survey was 

slightly modified from the instrument administered to over 2,200 U.S. respondents as 

reported in Axsen and Kurani (2008). This previous study included over-samples of 

California (n= 851) and Northern California (n=216) in the region along Interstate-80 

from the San Francisco Bay Area to the eastern reaches of the Sacramento conurbation. 

In this report, responses from these two samples are compared with the responses of 

Project participants. 

The primary survey instrument used in the PHEV Project is a set of two internet-based 

questionnaires, each requiring 20 to 30 minutes to complete: 1) background information, 

completed before the household drives the PHEV, and 2) plug-in hybrid electric vehicle 

(PHEV) designs, completed after the household has driven the PHEV for several weeks. 

Part One includes questions on vehicle ownership, knowledge of gasoline use and 

spending, knowledge of electricity use and spending, awareness of electric-drive 

vehicles, attitudes towards environmental and global issues, as well as household 

structure, income, education and other demographic variables. Awareness of electricdrive vehicles is assessed with questions eliciting the stated familiarity of respondents 

with conventional gasoline, hybrid-electric, electric, and plug-in hybrid electric vehicles. 

Respondents were then asked to demonstrate their understanding by choosing how each 

vehicle type could be fueled: with gasoline, electricity through an electrical outlet, or 

either. The implication of this exercise is not that consumers need to have a deep 

technological understanding of electric-drive vehicles in order to buy them. However, we 
 19 

feel that basic familiarity, i.e. whether or not the vehicle can be plugged in, may shape 

participants experience with the PHEV-conversion during their trial period and ultimately 

affect their PHEV design priorities.8

The Part Two questionnaire focuses on PHEV design priorities elicited in two versions of 

priority-evaluator games. Commonly, researchers will infer preferences for attributes of 

alternative fuelled vehicles by presenting participants with a description of one or several 

new technologies, followed with a set of hypothetical choice scenarios in which 

respondents make several choices from sets of vehicles of different attributes (see for 

example Bunch et al., 1993; Ewing and Sarigollu, 2000; Potogolou and Kanaroglou, 

2007). However, Heffner et al. (2007) demonstrate that more in-depth research, such as 

household interviews, can reveal important information that choice experiments cannot. 

To improve the quality of data gathered from Project participants, prior to the PHEV 

design exercises, participants were provided a PHEV buyers’ guide describing basic 

design options for PHEVs (replicated in Appendix B). Respondents then completed two 

PHEV design games (replicated in Appendix C). The first was a PHEV Development 

Priority game in which participants create PHEV designs over several iterations. Second 

was a Purchase Design game, similar to the first, but the design possibilities were priced 

in dollars and participants could reject buying a PHEV, retaining a conventional vehicle. 

One key difference between the games utilized in this study and a stated choice exercise 

is that the games are design exercises, not choice exercises. Rather than choose their 

preferred vehicle design from a limited set of options (typically repeated several times) 

specified by the researchers, participants in the design games have a design envelope 

available to them, and they construct their most favored design from within that envelope 

subject to resource constraints. Kurani et al. (1996) discussed the basis for regarding 

consumer evaluations, especially of novel products such as electric-drive vehicles, as 

being constructed in the process of choosing (or not choosing). 

 

8

 As asked of the prior national, statewide, and regional samples—who will not have experience with a 

PHEV afforded to Project participants—the question was intended only to test whether basic familiarity 

with electric-drive technologies affected PHEV design priorities. 
 20 

Both games focused on four PHEV design attributes: (1) hours required for complete 

recharge of a depleted battery, (2) gasoline use in CD mode, (3) miles of range in CD 

mode, and (4) gasoline use in CS mode. In each game, a base PHEV design is offered 

with capabilities easily achievable by current battery technology (Axsen et al., 2008): a 

PHEV that requires up to 8 hours to completely recharge, that can be driven for the first 

10 miles in CD mode using blended operation that increases gasoline-only fuel economy 

to 75 mpg, and that can improve fuel economy by 10 mpg when operating in CS mode 

over an otherwise similar conventional internal combustion engine vehicle.9

 In both 

games, participants were given opportunities to improve each attribute under different 

resource conditions. 

We chose these four attributes due to their importance in determining driving patterns as 

well as reflecting technological capabilities. First, the time to recharge a depleted battery 

in PHEVs more capable than the base design would take 6-8 hours, but technology exists 

to allow “fast” charging in less than one hour—allowing for significantly different 

recharge and driving patterns. Second, currently available PHEV conversions are 

designed to provide blended CD mode. We specified upgrades to account for several 

levels of gasoline-only fuel economy in blended operation: 75, 100, and 125 mpg. This 

range includes the 100 mpg “magic” number identified as important among some early 

PHEV conversion owners (Kurani et al., 2007). Because automakers such as General 

Motors have announced plans to release PHEVs designed for all-electric operation, we 

also include an all-electric CD upgrade option. Third, CD range depends on battery 

energy capacity, and proposed designs typically range from 10 to 40 miles (Pesaran et al., 

2007; Kromer and Heywood, 2007). The fourth category, fuel consumption in CS mode, 

is comparable to the operation of today’s hybrid electric vehicles; the battery and electric 

motor are used to improve the efficiency of the gasoline engine, not to use grid 

 

9

 Note that these PHEV design games are meant to represent a PHEV design space that is technologically 

feasible and that allows respondents to tell us which (and how much) of the four attributes are more or less 

important, but not necessarily to produce precise vehicle specifications. For instance, the battery required 

for our base PHEV design would likely require only 2 to 3 hours to fully recharge with a 110-volt circuit. 

However, based on pre-testing, we chose to simplify attribute levels and ignore potential interactions to 

create exercises that are more likely to be understood by our respondents. 
 21 

electricity. Most hybridized drivetrains can increase fuel economy by 10 to 30 miles per 

gallon (mpg) relative to a similar size, weight, and performance vehicle. 

The first exercise, the Development Priority game, presents participants with a 

hypothetical scenario: an existing household vehicle is to be upgraded to a PHEV at no 

cost.10 The performance and appearance of their vehicle would remain the same, except 

for the additional plug-in hybrid capabilities. Participants were presented with a base 

PHEV model and given points they must allocate among potential upgrades. Over five 

rounds of the Development Priority game, participants were provided progressively more 

points (Table 1). For the first three rounds of the game higher levels of upgrades of the 

four attributes and more combinations of upgrades were also offered, expanding the 

PHEV design envelope to observe participants’ allocation of resources. A screenshot of 

the game, along with the language used for respondents, is portrayed in Figure 4. 

Table 1: Upgrades for PHEV Development Priority game 

Attribute 

 (base value) 

Round One: 

(1 point) 

Round Two: 

(2 points) 

Rounds Three, Four 

and Five: 

(4, 6 and 8 points) 

Recharge time: 

 (8 hours) 

4 hours (1pt) 4 hours (1pt) 

2 hours (2pt) 

4 hours (1pt) 

2 hours (2pt) 

1 hour (3pt) 

Charge depleting (CD) 

mpg and type: 

 (75 mpg) 

100 mpg (1pt) 100 mpg (1pt) 

125 mpg (2pt) 

100 mpg (1pt) 

125 mpg (2pt) 

All-electric (4pt) 

CD range: 

 (10 miles) 

20 miles (1pt) 20 miles (1pt) 

40 miles (2pt) 

20 miles (1pt) 

40 miles (2pt) 

Charge sustaining (CS) 

mpg: 

 (Current mpg* +10) 

Current mpg 

 +20 (1pt) 

Current mpg 

 +20 (1pt) 

Current mpg 

 +30 (2pt) 

Current mpg 

 +20 (1pt) 

Current mpg 

 +30 (2pt) 

 

10 Which household vehicle was to be “upgraded” was determined in Part One of the survey as either the 

vehicle that the household most recently purchased, or, the newer vehicle that is most frequently driven 

(see the full survey in Appendix C). 
 22 

Figure 4: Screenshot of Development Priority game (Round Four) 

The second exercise, the Purchase Design game, framed the PHEV design exercise in the 

context of a future vehicle purchase. The questionnaire first elicited information about the 

anticipated price, make, and model of the next new vehicle the respondent’s household 

would likely buy. The respondent then completed two PHEV purchase exercises, each 

comparing their anticipated conventional vehicle with a PHEV version of the same. 

Participants were presented with a “higher” price and “lower” price PHEV purchase 

conditions, where prices in both conditions also depended on whether the vehicle was a 

car or truck (Table 2). As in the Development Priority game, each exercise started with 

the same base PHEV model, with additional upgrades available for added price. The 

participant could choose either their anticipated conventional vehicle, the offered (base) 

PHEV, or to upgrade the PHEV. Figure 5 is a screenshot of this exercise. 
 23 

Table 2: Price of upgrades for Purchase Design game 

 “Higher” price “Lower” price 

Attributes Attribute level Car Truck Car Truck 

Base premium 

over conventional 

 $3,000 $4,000 $2,000 $3,000 

Added premiums: 

Recharge time 8 hours 

4 hours 

2 hours 

1 hour

0 

+$500 

+$1,000 

+$1,500 

0 

+$1,000 

+$2,000 

+$3,000 

 0 

+$250 

+$500 

+$750 

0 

+$500 

+$1,000 

+$1,500 

CD mpg and type Blended 

 75 mpg 

 100 mpg 

 125 mpg 

All-electric 

0 

+$1,000 

+$2,000 

+$4,000 

0 

+$2,000 

+$4,000 

+$8,000 

 

0 

+$500 

+$1,000 

+$2,000 

0 

+$1,000 

+$2,000 

+$4,000 

CD range 10 miles 

20 miles 

40 miles 

0 

+$2,000 

+$4,000 

0 

+$4,000 

+$8,000 

 0 

+$1,000 

+$2,000 

0 

+$2,000 

+$4,000 

CS mpg Conventional mpg +10 

Conventional mpg +20 

Conventional mpg +30 

0 

+$500 

+$1,000 

0 

+$1,000 

+$2,000 

 0 

+$250 

+$500 

0 

+$500 

+$1,000 

Because battery and drivetrain costs are uncertain, upgrade prices in Table 2 are 

hypothetical. We are less concerned whether the prices we now present to participants 

will be right in a future (if and) when PHEVs are marketed, and more concerned with 

how participants respond in the PHEV design space within different price contexts. Still, 

the price contexts we present are not wholly imaginary. Overall, prices are based on short 

term (high price) and long term (low price) estimates from previous studies: Markel 

(2006) estimates incremental costs for PHEVs with all-electric capabilities (7 to 19 kWh) 

at $6,000 to $22,000, while Kalhammer et al. (2007) provide cost estimates for PHEVs 

with slightly lower capacity batteries (4 to 14 kWh) in the range of $2,000 to $8,000. 

Price premiums for PHEV designs in our survey ranged from $3,000 to $13,500 for cars 

in the “high” price condition, and from $2,000 to $7,250 in the “low” price condition. For 

trucks, base model PHEV prices are increased and upgrades doubled based on Duvall et 

al.’s (2002) estimates of a full size SUV PHEV requiring 75 percent more energy 

capacity and 190 percent more battery power to achieve the same CD performance as a 

compact car PHEV. 
 24 

Figure 5: Screenshot of Purchase Design game (“high” price, vehicle 

model customized for respondent) 

Who are the Project Participants? 

To explore whether findings from the Project can be generalized to other people, we 

describe briefly who the Project respondents are and how they compare to other larger 

samples. These include the California and northern California over-samples we surveyed 

during our nationally representative survey of new car buying households. Other 

comparisons are made to the 2001 Nationwide Household Travel Survey, the 2005-07 

American Community Survey, and the 2000 United States Census. 
 25 

Descriptions of the samples on the following attributes are presented in Table 3: 

household hybrid vehicle ownership, respondents’ gender, education, age, household 

income, and housing type. One important difference between the Project participants and 

all other samples is that Project participants are chosen, in part, because they have a place 

at home to recharge the PHEV—we judged it to be of little value to give a vehicle to a 

household who could not routinely and easily recharge the vehicle, if they chose to. This 

choice on our part will introduce some differences in income and housing type as seen in 

Table 3. Finally, the description of the Project households is highly provisional and will 

change by design over the remainder of the Project. 

Our sample contains about the same proportion of HEV owners as do our survey oversamples for northern California and California—but still, this is one HEV owner (to 

date). Though we cannot report hybrid vehicle ownership rates for the ACS or Census 

samples, it seems clear that all our survey and Project samples contain a higher 

proportion of hybrid owners than exist in the general population. Still, the overrepresentation is not so large as to skew overall responses. We expect that the percentage 

of hybrid owners in the Project sample will ultimately be higher than it is now. 

The gender balance of the present Project participants represents that of the general 

population and California over-sample; the northern California over-sample is skewed 

toward male respondents. The Project participants are skewed toward people with 

graduate educations—even compared to our survey over-samples, which are skewed 

toward higher education compared to the general population samples. Respondents in all 

three of our samples are much more likely to be between the ages of 35 and 54 than the 

general population; the skew toward this age group is even stronger in the present Project 

sample than in the survey over-samples. As with education and age, the present sample of 

Project participants amplifies the distinctions from the general population of the survey 

over-samples: the over-samples of new car buyers in California and northern California 

are more likely to have higher household incomes than the general population and the 

Project participants are even more likely to have higher incomes. As noted above, by 

design (or rather, because of known correlations between housing type and ability to 

recharge at home) our survey respondents are far more like to live in detached homes. 
Table 3: Comparing Project participants, survey respondents, and the general population

 26 

Target AAA members New vehicle buyers General population Year 2008-9 2007 2007 2001 2005-7 2000 Data source PHEV Demo PHEV Survey 

(Nor. Cal.)a

PHEV Survey

(Cal.)a

NHTSb 

(Cal.) 

 ACS f 

(Cal.) 

Census g 

(Cal.) 

Sample size 34 216 851 389 Hybrid owner? Yes 11.8% 8.9% 10.6% - - -Genderc Male 49.2% 59.7% 48.5% 44.5% 50.0% 49.7%  Female 50.8% 40.3% 51.5% 55.5% 50.0% 50.3% Educationd High school or lower 9.1% 2.6% 8.8% 22.1% 43.0% 43.3%  Some college 21.2% 34.9% 33.9% 22.1% 20.4% 22.9%  College degree 30.3% 32.8% 39.5% 39.9% 26.3% 24.2%  Graduate degree 39.4% 29.7% 17.8% 15.9% 10.4% 9.5% Agec 15 to 24 3.2% 4.6% 3.3% 6.5% 19.0% 18.3%  25 to 34 8.1% 21.1% 20.5% 18.0% 18.3% 19.8%  35 to 44 25.8% 27.3% 29.0% 23.5% 19.3% 21.6%  45 to 54 27.4% 29.4% 23.7% 24.8% 17.6% 16.5%  55 to 64 29.0% 10.8% 15.1% 13.3% 12.1% 9.9%  >64 6.5% 6.7% 8.3% 13.8% 13.8% 13.8% Household < 30 k 3.1% 1.8% 2.0% 6.3% 25.3% 31.2% income 30 k to 60 k 15.6% 11.9% 17.6% 23.4% 25.8% 29.5%  > 60k to 100k 15.6% 35.1% 27.7% 32.3% 23.0% 22.1%  > 100k 65.6% 51.2% 52.7% 38.0% 25.8% 17.3%  Mean incomee $117,734 $106,949 $104,814 $84,416 $73,944 $61,441 

Ratio of mean incomes (new vehicle buyer/gen. pop.) 1.59 1.45 1.42 1.37 

Housing typed Detached house 94.1% 71.3% 68.1% 79.4% 58.0%  Attached house 5.9% 10.3% 11.9% 4.4% 7.0%  Apartment 0% 17.9% 16.7% 13.6% 30.7%  Mobile home 0% 0.5% 3.4% 2.6% 4.2% 

a U.S. weights provided by Harris Interactive. b NHTS sample limited to responding California households that had purchased a vehicle of model year 2001 or 2002. c For PHEV Project: data reported for all participants; for PHEV survey: data only reported for responding member of household. d For PHEV Project and PHEV survey: data only reported for responding member of household. e Mean approximated from the product of middle values assigned to each income category and the proportion of the sample in that category. f 2005-2007 American Community Survey 3-year estimates, California.

g 2000 Census by the U.S. Census Bureau. 
 27 

Gasoline Prices Faced by Survey Respondents and Project Participants 

One question we are repeatedly asked regarding the national study is, “When was it done 

in comparison to the run-up of gasoline prices to past $4.00 per gallon during the summer 

of 2008?” The answer is that the national survey was conducted in December 2007 and 

precedes the rise of gasoline prices past $4.00 per gallon by several months. The average 

price last paid for gasoline by the California and northern California samples were both 

about $3.40 per gallon as shown by the horizontal lines in Figure 6. 

Figure 6: Comparing gasoline prices from survey respondents (lines) and 

Project participants (diamonds) 

$-

$0.50

$1.00

$1.50

$2.00

$2.50

$3.00

$3.50

$4.00

$4.50

$5.00

2-Aug-08 1-Sep-08 1-Oct-08 31-Oct-08 30-Nov-08 30-Dec-08 29-Jan-09 28-Feb-09

Date

$/Gallon

Survey Average, December 2007 (All California)

Survey Average, December 2007 (North California)

$-

$0.50

$1.00

$1.50

$2.00

$2.50

$3.00

$3.50

$4.00

$4.50

$5.00

2-Aug-08 1-Sep-08 1-Oct-08 31-Oct-08 30-Nov-08 30-Dec-08 29-Jan-09 28-Feb-09

Date

$/Gallon

Survey Average, December 2007 (All California)

Survey Average, December 2007 (North California)

In contrast, the first Project participants were paying well in excess of $4.00 per gallon 

for gasoline in August 2008. But these are a small minority of Project participants, as 

prices quickly declined through September and October 2008 to, and then below, the 

average of the price faced by the national survey respondents. Still, whether they faced 

higher gasoline prices during their PHEV trial period or whether they simply recall such 

higher prices from last summer, we expect that our Project participants may be more 

sensitive to the uncertainty of gasoline prices than the national survey respondents were 

at that time. This may make Project participants less like our survey respondents, but 
 28 

makes them more like their peers, i.e., all car-buying households, who have now lived 

through this same price history. 

Motivations and Knowledge regarding Electric-drive 

The invitation sent by AAA Northern California, Nevada & Utah did not emphasize 

motivations to volunteer; still, one might speculate that the households volunteering for a 

PHEV demonstration project have stronger motivations and knowledge regarding 

electric-drive vehicles than households in general. Responses to three questions regarding 

motivations are summarized in Figure 7: global warming, air pollution, and energy 

(in)dependence. The Project sample contains a slightly higher percentage of people who 

state that each of these three issues is “a serious problem, and immediate action is 

necessary” than in the California and northern California survey samples. Still the 

differences are small. We judge the differences to be unlikely to make a substantive 

difference in any conclusions we may draw between the samples on their PHEV designs. 

On the issue of knowledge regarding electric-drive vehicles, a question in the first part of 

the questionnaire completed by both the survey sample and Project participants asked 

respondents to rate their familiarity with conventional, electric, hybrid-electric, and plugin hybrid vehicles. This was followed up by a question asking how each of these four 

types of vehicles are fueled and/or recharged. Responses to this second question are 

summarized in Figure 8. In general, there is little to distinguish the knowledge of electric 

drive vehicles among the Project participants from the survey respondents—except on the 

specific issue of plug-in hybrids. Across all samples, very high percentages of 

respondents know that a plug-in hybrid can be both fueled and plugged-in; the highest 

percentage is among our Project participants. There are a few opportunities for 

“information leaks” to the project households about PHEVs—the recruiting phone call 

and the information provided to households when the PHEV is first delivered. 
 29 

Figure 7: Comparing environmental beliefs among survey respondents 

(“CA” and “NCA”) and Project participants (“Demo”) 

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

CA

NCA

Demo

CA

NCA

Demo

CA

NCA

Demo

% Choosing Statement

It is a serious problem, and

immediate action is necessary.

It could be a serious problem,

and we should take some

action now.

It is not a problem and does not

require any action.

More research is needed

before action is taken.

Global warming

(climate change)

Air pollution The dependency

of the U.S. on

foreign oil

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

CA

NCA

Demo

CA

NCA

Demo

CA

NCA

Demo

% Choosing Statement

It is a serious problem, and

immediate action is necessary.

It could be a serious problem,

and we should take some

action now.

It is not a problem and does not

require any action.

More research is needed

before action is taken.

Global warming

(climate change)

Air pollution The dependency

of the U.S. on

foreign oil

Figure 8: Comparing electric-drive knowledge among survey respondents 

(CA and NCA) and Project participants (“Demo”): “From what you 

understand of these vehicle technologies, which can use fuel, and which 

can be plugged in?” 

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

CA

NCA

Demo

CA

NCA

Demo

CA

NCA

Demo

CA

NCA

Demo

% Choosing Statement

Only with

gasoline

Only by plugging

in

Either

Conventional

vehicle (CV)

Electric

vehicle (EV)

Hybrid-electric

vehicle (HEV)

Plug-in hybrid

vehicle (PHEV)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

CA

NCA

Demo

CA

NCA

Demo

CA

NCA

Demo

CA

NCA

Demo

% Choosing Statement

Only with

gasoline

Only by plugging

in

Either

Conventional

vehicle (CV)

Electric

vehicle (EV)

Hybrid-electric

vehicle (HEV)

Plug-in hybrid

vehicle (PHEV)
 30 

3A. PROJECT RESULTS: PHEV DESIGNS

All participants in the Project and in the prior survey research created PHEV designs. We 

use these designs as measures of what is interesting and valuable to respondents about 

PHEVs. In addition to our inherent interest in the PHEV designs created by the Project 

participants, we are interested in whether and how the Project participants’ designs differ 

from those created by the prior survey respondents. 

Whose PHEVs? Plausible early markets 

This section compares the PHEV designs elicited from the 34 households who completed 

their Project participation between August 2008 and April 2009 with those elicited from 

respondents in the California (CA) and northern California (NCA) over-samples of the 

national survey in December 2007. The PHEV design games were described in the 

previous section, and reproduced in Appendices B and C. In this section, PHEV design 

priorities are reported only for respondents classified as plausible early market PHEV 

buyers by satisfying two requirements: 1) they demonstrate access to sufficient recharge 

infrastructure, defined here as home access to an electrical outlet for their vehicle, and 2) 

interest in PHEVs as indicated by a reported purchase intention in the “higher” price 

condition of the Purchase Design game. Based on these conditions, Axsen and Kurani 

(2008) described 33.5 percent of responding U.S. new car buyers as plausible early 

market respondents. In the California over-sample, 45.8 percent of respondents park their 

vehicle within 25 feet of an electrical outlet at home, and of these, 73.5 percent indicate 

PHEV purchase intention in the “higher” price scenario, and thus 33.7 percent of the total 

California sample are classified as the plausible early market respondents (n=286). In the 

northern California over-sample, 45.6 percent have home recharge access, 71.3 percent of 

which indicate a PHEV purchase intention, and thus 32.5 percent of the total sample is 

classified as plausible early market respondents (n=63).11 Among the PHEV Project 

 

11 Because of the small samples for the households who completed their Project participation by April 2009 

and for the plausible early market respondents in northern California, the comparisons made here are 

descriptive and exploratory rather than (necessarily) representative. 
 31 

participants, all have access to home recharging because it is a requirement for 

participation. Among these 34 households, 30 (88 percent) indicate a PHEV purchase 

intention in the higher price scenario and thus these 88 percent are included as the 

plausible early market Project participants. Clearly nothing about the likeliness to design 

a PHEV as their plausible next new vehicle purchase distinguishes the California and 

Northern California survey samples from the national sample; equally clearly, Project 

participants are more likely to design their next new car as a PHEV. Given they are more 

likely to design a PHEV, are our Project households designing different PHEVs than did 

our survey respondents? 

What PHEVs do they Design? 

The PHEV Purchase Design game first asks households to select a vehicle they were 

most likely to buy next. Figure 9 compares these base vehicles selected by survey 

respondents with those selected Project participants. Notably, 67 percent of Project 

participants selected some variety of HEV and 40 percent selected a Toyota Prius. These 

percentages are 2 to 3.5 times higher than those of the CA and NCA samples, indicating a 

much more frequent interest in hybrid vehicles among Project participants (after their 

PHEV trial) than was elicited from a broader samples of CA and NCA car buyers (who 

lacked direct experience with a PHEV). This difference may not be due to a 

predisposition and/or self-selection of Project participants. Recall from their previous 

description that Project participants: are not substantially more likely to own a hybrid, do 

not possess more knowledge about electric drive vehicles, and do not have more concern 

for environmental or global issues—at least not to such a degree as to warrant a 2 to 3.5 

fold increase in hybrid interest in these design games. One explanation supported by the 

household interviews that because Project participants completed the PHEV Purchase 

Design game after driving the PHEV-conversion for several weeks, participants had 

become more interested in hybrids in general, and in the Toyota Prius in particular. 
 32 

Figure 9: Comparing base vehicles chosen for PHEV Purchase Design 

Game (plausible early market only: CA, n=286; NCA, n=63; Project, n=30) 

0%

20%

40%

60%

80%

100%

CA NCA Demo

Sample

Base Vehicle for Future 

Purchase (% of Sample)

Conventional

Car

Conventional

Truck

Toyota Prius

Other HEV

Focusing on the interests of these plausible early market Project participants, results of 

the two PHEV design games are summarized in Figure 10. In Round One of the 

Development Priority game, respondents were given one point to allocate towards one 

upgrade to the base PHEV model. As described previously, four upgrades were available: 

recharge time (from 8 to 4 hours), gasoline-fuel economy during CD mode (from 75 to 

100 mpg), CD range (from 10 to 20 miles), or CS gasoline-fuel economy (from 10 to 20 

mpg over the conventional version of the vehicle). Improving the CD range was the most 

frequently chosen upgrade (50.0 percent), while improving CS fuel economy was a close 

second place (39.3 percent).12 The general ranking of attribute upgrades in Round One 

continues through later rounds: a higher percentage of potential early market respondents 

designed PHEVs with CD range upgrades and CS fuel economy upgrades, as well as CD 

type in later rounds, and few respondents designed PHEVs with faster recharge times. 

 

12 Although the percentages add up to 100 across the columns in Round One, they do not in further Rounds 

because respondents have enough points to choose multiple upgrades. 
 33 

Figure 10: Upgrades selected in PHEV design games by Project 

participants (plausible early market Project participants only, n=28) 

0%

20%

40%

60%

80%

100%

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Base Model

Recharge

CD Type

CD Range

CS MPG

Base Model

% Choosing Upgrad

e

Base Model

3rd Level Upgrade

2nd Level Upgrade

1st Level Upgrade

Game 1: Development Priority (Points) Game 2: Purchase Design ($)

Round 1

(1pt)

Round 2

(2pt)

Round 3

(4pt)

Round 4

(6pt)

Round 5

(8pt)

“High”

Price

“Low”

Price

0%

20%

40%

60%

80%

100%

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Base Model

Recharge

CD Type

CD Range

CS MPG

Base Model

% Choosing Upgrad

e

Base Model

3rd Level Upgrade

2nd Level Upgrade

1st Level Upgrade

Game 1: Development Priority (Points) Game 2: Purchase Design ($)

Round 1

(1pt)

Round 2

(2pt)

Round 3

(4pt)

Round 4

(6pt)

Round 5

(8pt)

“High”

Price

“Low”

Price

All-electric operation (in CD mode) was first offered to respondents in Round Three of 

the Development Priority game; only one of the 28 households (3.6 percent) incorporated 

this upgrade into their PHEV, which came at the expense of any other upgrades available 

in prior rounds.13 In Round Four, the number of plausible early market Project 

participants designing a PHEV with all-electric operation rose to six (21.4 percent). 

Figure 11 portrays the 23 different possible PHEV designs possible in Round Four. This 

is the first round in which the design envelope allows a PHEV with 40 miles of allelectric range—a vehicle performance (at least as measured by CD mode and range) 

similar to GM’s Volt concept. Only three of plausible early market Project participants 

(10.7 percent) created this specific design. Overall, all-electric operation was not a 

chosen frequently when points were relatively scarce and alternative design possibilities 

were available, i.e. in Rounds Three and Four of the Design Priority game. PHEV 

 

13 Although 30 households were previously identified earlier as the plausible early market PHEV demo 

participants, data from the development priority game (game 1) are only reported for 28 households due to 

missing data (Figure 10, Figure 11, and Figure 13). 
 34 

performance priorities varied substantially; no single PHEV design emerged as a majority 

favorite. Still, the Project sample to date is the most heavily skewed toward a single 

design, i.e., 8 hours recharging, 125mpg for 40 miles in CD operation, and +30 mpg in 

CS operation (compare to Figures 14 and 15). 

Figure 11: Distribution of selected PHEV designs in Round Four of 

Development game (plausible early market only: Project, n=28) 

0% 10% 20% 30% 40% 50%

2 Hours_75 MPG_40 Miles_+30 MPG

1 Hours_75 MPG_40 Miles_+20 MPG

1 Hours_75 MPG_20 Miles_+30 MPG

4 Hours_100 MPG_40 Miles_+30 MPG

2 Hours_100 MPG_40 Miles_+20 MPG

2 Hours_100 MPG_20 Miles_+30 MPG

1 Hours_100 MPG_40 Miles_+10 MPG

1 Hours_100 MPG_20 Miles_+20 MPG

1 Hours_100 MPG_10 Miles_+30 MPG

8 Hours_125 MPG_40 Miles_+30 MPG

4 Hours_125 MPG_40 Miles_+20 MPG

4 Hours_125 MPG_20 Miles_+30 MPG

2 Hours_125 MPG_40 Miles_+10 MPG

2 Hours_125 MPG_20 Miles_+20 MPG

2 Hours_125 MPG_10 Miles_+30 MPG

1 Hours_125 MPG_20 Miles_+10 MPG

1 Hours_125 MPG_10 Miles_+20 MPG

8 Hours_Electric Only_20 Miles_+20 MPG

8 Hours_Electric Only_10 Miles_+30 MPG

4 Hours_Electric Only_20 Miles_+10 MPG

4 Hours_Electric Only_10 Miles_+20 MPG

2 Hours_Electric Only_10 Miles_+10 MPG

8 Hours_Electric Only_40 Miles_+10 MPG

As previously noted, results of the Purchase Design game suggest that the majority of 

Project participants would value PHEV capabilities in their next vehicle. Figure 10 also 

depicts the proportion of upgrades chosen in the price conditions for this second version 

of a PHEV design game. Seven of plausible early market Project participants (25 

percent) chose the base PHEV models with no upgrade in both price conditions. Among 

those who created higher cost designs, overall patterns of these designs are similar to 

those created in the Development Priority game; CS fuel economy upgrades were chosen 

more often than other upgrades, and there is no evidence of the strong interest in all75 mpg 

100 mpg 

125 mpg 

Electric 

O l

PHEV Design Combination: 

(Recharge_CD Type_CD Range_CS MPG) 

% of Respondents Choosing Design 

"Volt" Design: 

Recharge = 8 hours 

CD Type = Electric Only 

CD Range = 40 miles 

CS mpg = +10 mpg
 35 

electric operation observed among some pioneer PHEV conversion drivers (Kurani et al., 

2007). All-electric upgrades were chosen by two households (seven percent) and four 

households (13 percent) in the higher and lower price conditions, respectively. 

Figure 12 depicts the proportion of CD type and CD range designs selected by Project 

participants. Note that 11 households (37 percent) designed a PHEV capable of 75 mpg 

for the first 10 miles, and that 24 households (86 percent) designed a blended CD design 

(as opposed to all-electric) with a range of 20 miles or less. Such designs have far lower 

battery requirements than the all-electric, longer-range designs assumed by various 

battery experts (Axsen et al., 2008). 

Figure 13 compares Round 4 of the Development Priority game results from plausible 

early market Project participants with those respondents from the CA and NCA samples. 

Results are fairly similar across samples, though Project participants selected recharge 

upgrades less frequently, and selected 100 CD mpg and +30 CS mpg more frequently. 

Figures 14 and 15 show the distribution of PHEV designs in Round Four in the CA and 

NCA samples, respectively for comparison to Figure 10. 

All figures indicate a wide variety of PHEV design interests among households, without 

any particular draw to the all-electric 40-mile “Volt” concept. Figure 16 compares the 

same samples in terms of the higher price scenario of the PHEV Purchase Design game, 

where a substantially higher proportion of Project participants selected some level of CD 

type and range upgrades. Several differences among samples could contribute to this 

trend; Project participants have: higher household income (as portrayed in Table 3) and 

more experience with PHEV driving (having actually driven a PHEV for several weeks), 

as well as other potential differences in driving patterns, commute patterns or other 

factors that were not measured in all three samples. 
 36 

Figure 12: Distribution of selected PHEV designs in high price scenario of 

Purchase Design Game (plausible early market Project participants only, 

n=30) 

   ' 

	

	

	

75 MPG

100 MPG

125 MPG

All-Electric

37% designed PHEV

with 10 mile range of 75 mpg

   ' 

	

	

	

75 MPG

100 MPG

125 MPG

All-Electric

37% designed PHEV

with 10 mile range of 75 mpg

Figure 13: Comparing upgrades selected in Round 4 of Development 

Priority game, (plausible early market only: CA, n=286; NCA, n=63; Project, 

n=28 

0%

20%

40%

60%

80%

100%

CA

NCA

Demo

CA

NCA

Demo

CA

NCA

Demo

CA

NCA

Demo

% Choosing Upgrade

3rd Level Upgrade

2nd Level Upgrade

1st Level Upgrade

Recharge

(4h, 2h, 1h)

CD MPG

(100, 125, AE)

CD Range

(20, 40 miles))

CS MPG

(+20, +30)

0%

20%

40%

60%

80%

100%

CA

NCA

Demo

CA

NCA

Demo

CA

NCA

Demo

CA

NCA

Demo

% Choosing Upgrade

3rd Level Upgrade

2nd Level Upgrade

1st Level Upgrade

Recharge

(4h, 2h, 1h)

CD MPG

(100, 125, AE)

CD Range

(20, 40 miles))

CS MPG

(+20, +30)
 37 

Figure 14: California Distribution of selected PHEV designs in Round Four 

of Development game (plausible early market only: CA, n=286) 

0% 10% 20% 30% 40% 50%

2 Hours_75 MPG_40 Miles_+30 MPG

1 Hours_75 MPG_40 Miles_+20 MPG

1 Hours_75 MPG_20 Miles_+30 MPG

4 Hours_100 MPG_40 Miles_+30 MPG

2 Hours_100 MPG_40 Miles_+20 MPG

2 Hours_100 MPG_20 Miles_+30 MPG

1 Hours_100 MPG_40 Miles_+10 MPG

1 Hours_100 MPG_20 Miles_+20 MPG

1 Hours_100 MPG_10 Miles_+30 MPG

8 Hours_125 MPG_40 Miles_+30 MPG

4 Hours_125 MPG_40 Miles_+20 MPG

4 Hours_125 MPG_20 Miles_+30 MPG

2 Hours_125 MPG_40 Miles_+10 MPG

2 Hours_125 MPG_20 Miles_+20 MPG

2 Hours_125 MPG_10 Miles_+30 MPG

1 Hours_125 MPG_20 Miles_+10 MPG

1 Hours_125 MPG_10 Miles_+20 MPG

8 Hours_Electric Only_20 Miles_+20 MPG

8 Hours_Electric Only_10 Miles_+30 MPG

4 Hours_Electric Only_20 Miles_+10 MPG

4 Hours_Electric Only_10 Miles_+20 MPG

2 Hours_Electric Only_10 Miles_+10 MPG

8 Hours_Electric Only_40 Miles_+10 MPG

% of Respondents Choosing Design 

PHEV Design Combination: 

(Recharge_CD Type_CD Range_CS MPG) 

"Volt" Design 

75 mpg 

100 mpg 

125 mpg 

Electric 

Only 
 38 

Figure 15: Northern California Distribution of selected PHEV designs in 

Round Four of Development game (plausible early market only: NCA, n=63) 

0% 10% 20% 30% 40% 50%

2 Hours_75 MPG_40 Miles_+30 MPG

1 Hours_75 MPG_40 Miles_+20 MPG

1 Hours_75 MPG_20 Miles_+30 MPG

4 Hours_100 MPG_40 Miles_+30 MPG

2 Hours_100 MPG_40 Miles_+20 MPG

2 Hours_100 MPG_20 Miles_+30 MPG

1 Hours_100 MPG_40 Miles_+10 MPG

1 Hours_100 MPG_20 Miles_+20 MPG

1 Hours_100 MPG_10 Miles_+30 MPG

8 Hours_125 MPG_40 Miles_+30 MPG

4 Hours_125 MPG_40 Miles_+20 MPG

4 Hours_125 MPG_20 Miles_+30 MPG

2 Hours_125 MPG_40 Miles_+10 MPG

2 Hours_125 MPG_20 Miles_+20 MPG

2 Hours_125 MPG_10 Miles_+30 MPG

1 Hours_125 MPG_20 Miles_+10 MPG

1 Hours_125 MPG_10 Miles_+20 MPG

8 Hours_Electric Only_20 Miles_+20 MPG

8 Hours_Electric Only_10 Miles_+30 MPG

4 Hours_Electric Only_20 Miles_+10 MPG

4 Hours_Electric Only_10 Miles_+20 MPG

2 Hours_Electric Only_10 Miles_+10 MPG

8 Hours_Electric Only_40 Miles_+10 MPG

Figure 16: Three-Sample Comparison of upgrades selected in higher price 

scenario of Purchase Design game (plausible early market only: CA, n=286; 

NCA, n=63; Project, n=30) 

0%

20%

40%

60%

80%

100%

CA

NCA

Demo

CA

NCA

Demo

CA

NCA

Demo

CA

NCA

Demo

CA

NCA

Demo

% Choosing Upgrade

Base Model Only

3rd Level Upgrade

2nd Level Upgrade

1st Level Upgrade

Recharge

(4h, 2h, 1h)

CD Type

(100, 125, AE)

CD Range

(20, 40 miles))

CS MPG

(+20, +30)

No Upgrades

0%

20%

40%

60%

80%

100%

CA

NCA

Demo

CA

NCA

Demo

CA

NCA

Demo

CA

NCA

Demo

CA

NCA

Demo

% Choosing Upgrade

Base Model Only

3rd Level Upgrade

2nd Level Upgrade

1st Level Upgrade

Recharge

(4h, 2h, 1h)

CD Type

(100, 125, AE)

CD Range

(20, 40 miles))

CS MPG

(+20, +30)

No Upgrades

75 mpg 

100 mpg 

125 mpg 

Electric 

Only 

% of Respondents Choosing Design 

"Volt" Design 

PHEV Design Combination: 

(Recharge_CD Type_CD Range_CS MPG) 
 39 

PHEV Design Conclusions 

In summary, the variety of PHEV designs created by survey respondents and Project 

participants suggests there is still opportunity for automakers to explore and develop 

different PHEV designs. We found little evidence of inherent demand for all-electric 

operation in CD mode, even among Project participants who had experience driving a 

(CD blended-operation) PHEV for a month—though our Project cannot presently exclude 

the possibility of participants anchoring on what we have now made familiar to them, i.e., 

blended rather than all-electric CD operation. An even smaller subset was interested in 

creating a vehicle with performance attributes combining 40 miles of CD range with allelectric CD operation. These patterns contrast with the findings of Kurani et al.’s (2007) 

interviews with “pioneer” PHEV conversion drivers who exhibited strong interest in 

maximizing CD range and moving toward all-electric operation—effectively to approach 

the capabilities of pure electric vehicles. This difference suggests that while all-electric 

CD operation may be particularly attractive to a small subset of consumers, including 

those who already have extensive knowledge and experience with electric vehicles, at 

this point in time most households who buy new vehicles are more interested in high fuel 

economy, even after completing a multi-week trial with one PHEV incarnation. 

Participation in the Project appears to have decreased the importance of improvements in 

recharging rates compared to prior survey respondents, but keep in mind Project 

participants are selected in part because they are able to recharge at home. Project 

participants are somewhat more likely to design a PHEV for their next new vehicle—

rather than revert to a conventional vehicle—than are the survey respondents. Project 

participants are also more likely to choose a HEV as their base new vehicle from which 

to consider the design of a PHEV. 

The wide variety of PHEV designs created by survey respondents and Project participants 

support the notion of a “blank slate” early PHEV market, where early buyers may have 

little in the way of PHEV performance expectations. That is, not only is there room for a 

variety of technical pathways, but also there is room for multiple meanings of PHEVs. 

Desired PHEV designs and capabilities may be subject to change. Project participants 
 40 

and survey respondents had little pre-existing understanding of PHEVs and the responses 

we elicited are sensitive to the PHEV information and experience we did provide. As 

information about PHEV technology, costs, benefits, and meanings are transmitted 

throughout the population, interest in particular PHEV attributes and performances could 

shift too. For example, all-electric CD operation could become more meaningful to, and 

valued by, car buyers as they gain experience with all-electric driving and as they 

participate in the process of identifying just what all-electric operation means to people. 

Our respondents PHEV designs suggest the possibility of a trajectory over time of PHEV 

and electric-drive market development. Our respondents are designing PHEVs that are far 

more technologically and financially feasible than “experts” assume. In particular, most 

of those designs provide some all-electric driving, as even PHEVs that use blended 

operation in CD mode afford some all-electric driving. If we start with these less 

aggressively electric designs, then over subsequent market and vehicle generations, the 

electric capabilities of PHEVs can be increased as costs come down—due to learning by 

doing, technology development, and improved designs—at the same time that more 

consumers have learned to value increased electric-drive capabilities. 
 41 

3B. PROJECT RESULTS: RECHARGING

PHEVs provide some degree of fuel flexibility to consumers, giving them the option of 

using gasoline and grid-generated electricity. Given that the effects of PHEVs on energy 

use, the environment, and the electricity grid depend on driving and recharging 

behaviors, there is particular interest in how often PHEV owners will recharge a vehicle 

that does not have to be recharged and when PHEV owners will recharge their vehicles. 

The “fuel” mix and the carbon content of the electricity used to recharge electric-drive 

vehicles will vary according to how often, when, and where vehicles are recharged. 

Furthermore, in examining future “smart grid” scenarios in which vehicles may act as 

mobile power sources (or sinks), it is important to begin to replace analysts’ assumptions 

with measures of PHEV owners’ driving and recharging behaviors. From the 34 

households-to-date, we have obtained detailed information about their driving and 

recharging behaviors. In this section, we summarize how participants, with minimum 

input from researchers, acted with regards to the frequency, time of day, and location of 

recharging. 

Drivers in this Project have the option of recharging a vehicle to decrease gasoline use 

and increase electricity consumption for the duration of the supplemental battery’s 

charge. Recall, the PHEV-conversions used in this Project provide blended operation in 

CD mode: the cars are still subject to the underlying HEV hardware and software. During 

CD mode these PHEV-conversions will blend in more electricity than does a 

conventional Prius (which operates only in CS operation). Like a conventional Prius, it is 

practically difficult to achieve sustained all-electric driving in real-world conditions. 

All figures presented in this section are based on the last week of each household’s trial 

with the PHEV conversion. This provides a common period over which we can compare 

the same number of days and days of the week from each household. Also, the last week 

represents the highest degree of uniformity of understanding about recharging behavior 

across the households. Finally, since we judge that the households had developed their 

recharging habits by this last week (or had developed their habits as much as they were 

going to in the course of their PHEV trial), we view their final week with the PHEV as 
 42 

most representative of how these vehicles would be recharged by the households in the 

future. This judgment is generally confirmed by the household interviews. 

Perhaps more than any other information presented in this report, readers are cautioned 

against generalizing our observations here to all PHEVs and users. Daily life provides 

rhythms and routines that might shape behavior, for example the PHEV recharging 

frequency discussed next. Still, we believe that PHEV recharging behavior may also be 

shaped by the relationship between personal and household travel on the one hand and 

PHEV designs, especially all-electric vs. blended CD operation and CD range, on the 

other. For example, while the weight of evidence gathered so far in this Project suggests 

that households owning PHEVs will, on average, plug-in the PHEV more than once per 

day in an unconstrained world (as will be detailed next), we are not yet prepared to 

dismiss the argument that if these households had been given PHEVs with a different CD 

range, the frequency of households plugging in different PHEVs to the electric grid may 

be different than we observed.14

How often do People Plug-in their PHEV-conversions? 

The frequency with which people plug-in PHEVs to the electrical grid is perhaps the 

central daily behavior affecting the energy, environmental, and social benefits of PHEVs. 

Other important behaviors include the purchase of a PHEV whose CD range allows the 

household to accomplish the greatest proportion of miles driven in CD mode (constrained 

by the expense of buying too much CD driving range) before their next recharge 

opportunity and driving behaviors affecting overall efficiency, notably accelerations, top 

speeds, and routes. The context for interpreting the PHEV recharging behavior observed 

to-date in this Project is as follows. First, the only participants in this Project are people 

who can recharge a PHEV at their home. Second, as most households lacked a sense of 

the etiquette that would shape recharging at away-from-home locations, less away-from-

 

14 We use the phrase “plugging-in” to refer to all acts of connecting the vehicle to the electrical grid, 

regardless of the final state of charge of the battery when the vehicle is unplugged. We do this to create a 

more general category that contains both “recharging,” with its connotations of returning the battery to 100 

percent SOC, and partial recharging, in which the vehicle is unplugged and driven before the battery 

reaches 100 percent SOC. 
 43 

home recharging was observed than may otherwise occur in a world where the rules and 

conventions are known. Households who noticed “EV” parking and recharging spaces 

often asked us whether they could park and charge their PHEVs in such spaces. The few 

bolder individual who tried discovered that such spaces presently lack 110-volt outlets 

suitable for the PHEVs they were driving. Many people said they were uncertain of the 

propriety of asking friends, acquaintances, and business-owners to recharge. (See the 

discussion of recharging etiquette in the later section on narratives.) Third, no household 

was provided with time-of-day electricity tariffs. The second and third are related in that 

some away-from-home recharging opportunities such as workplaces would most often be 

used during the day (when electricity rates would presumably be higher, especially 

during afternoons and early evenings, under time-of-day electricity tariffs). PHEV drivers 

would then face countervailing signals—maximizing their PHEV benefits by plugging in 

more, but having to pay a higher price than nighttime electricity in order to do so. In 

short, the recharging frequency data reported here is from households who can recharge 

at home, whose recharging frequency is constrained by a general lack of away-fromhome recharging opportunities created by the lack of both physical infrastructure and 

social norms, but unconstrained by differential electricity prices. 

We calculate the mean number of times per day each household plugged-in their PHEV 

on weekdays and weekend days and plot the resulting frequency distributions in Figure 

17. As explained above, the figures are based on only the final week of each household’s 

experience with the PHEV-conversion. The weekday distribution ranges from zero to 2.6 

instances of plugging-in per day. (The zero-value for weekdays is from one household 

who determined that recharging made too little difference (compared to the substitution 

of an HEV into their household fleet) to make it worthwhile.) The mean of the weekday 

distribution is slightly more than one plug-in event per day (1.05), 14 households (41 

percent) were plugging in their PHEV more than once per day, on average across 

weekdays.15

 

15 We observed a difference in mean recharging frequency across weekdays from a high of 1.24 recharges 

per household on Wednesday to a low of 0.88 on Thursday. However, we presently regard this fine a level 

of analysis to be provisional and hypothetical 
 44 

Figure 17: Mean Daily Household Recharging Frequency Distributions, 

Weekdays and Weekend Days, Percent 

0%

10%

20%

30%

40%

50%

0 0<0.5 0.5<1.0 1.0<1.5 1.5<2.0 2.0<2.5 2.5<3.0

Mean Plugging-in events, per day

Weekdays Weekend Days

Plugging-in occurs less frequently on weekend days than on weekdays. Notably, onefourth the sample did not plug-in their PHEV on either weekend day; the high-end of the 

range was 1.5 times per weekend day. The mean number of times a PHEV was pluggedin per household was 0.82 per weekend day; nine households (27 percent) did so more 

than once per day. The two biggest causes of the lower mean weekend frequency were 1) 

the absence of recharging at work by two households, i.e., two households who plugged 

in at least twice a day on weekdays because they were plugging-in at home and work 

recharged less frequently on weekend days because work was not available to them as an 

alternative recharging location, and the higher likeliness in several households of not 

recharging at home on weekends because the PHEV was not at home at least one 
 45 

weekend evening. The PHEVs were often taken on out-of-town trips on weekends, but 

were rarely if ever charged during these long, and often overnight, trips.16

Electricity Availability And Instantaneous Power Demand 

To describe recharging behavior observed during each household’s demonstration, we 

have summarized information in two additional measures: electricity availability and 

instantaneous power demand. We define electricity availability as the time of day during 

which the vehicle was plugged into an electrical outlet. Conceptually, this means that the 

vehicle could be at any stage in its recharging cycle, available battery capacity, or at any 

location—so long as it is connected to the grid, electricity is available to the vehicle. We 

define instantaneous power demand as the power drawn from the grid to recharge the 

supplemental PHEV battery. The observed average recharging rates for these PHEVconversions were observed to vary across households—generally falling between 900 and 

1200 watts. In order to compare and summarize across households, instantaneous power 

demand is standardized (by assumption) to be the nominal average recharging rate of 

1000 watts. Additional parasitic loads from the battery cooling system, in the range of 30 

to 50 Watts, and brief periods of higher demand during the initial phases of battery 

charging and longer periods of lower demand during trickle charge at end of the charging 

cycle respectively have been ignored.17 

The electricity availability and instantaneous power demand are represented as the 

percentage of vehicle users plugged in and the average instantaneous power demand 

(summed across households) at a specific time of day respectively, between 12:00 AM to 

12:00 PM across all weekdays and weekend days. Average electricity availability and 

summed instantaneous power demand for every day of the week are in the Appendix E. 

 

16 The latter reason is supported by the fact that the average number of recharging events per household was 

higher on Sundays (0.94) than Saturdays (0.71)—consistent with a PHEV returning on Sunday from an 

overnight trip that started on Saturday. As in the prior footnote though, such differences between days are 

provisional, and in this case must be regarded as supportive, but not conclusive evidence. 

17 When we have ascertained whether the differences in the observed average recharging rates are due to 

differences across electrical outlets, vehicles, or both, we will provide a more refined analysis of power 

demand. Still, the broad behaviors described here have greater import for other analytical work than do the 

precise specifications of power demand for the specific combination of battery and recharger employed in 

these particular vehicles. 
 46 

Electricity Availability & Instantaneous Power Demand: All Weekdays 

Treating all households’ last week of driving the PHEV as if it had occurred during the 

same calendar week and all weekdays as if they were equivalent, Figure 18 displays the 

percentage of vehicles plugged in at a given time of day for all weekdays (in red, and on 

the left axis) and the instantaneous power demand summed over the households and 

averaged over weekdays (in blue, and on the right axis). As the red line shows, across the 

170 weekdays represented in Figure 18 (34 households times 5 weekdays), 70 percent of 

households had plugged in their PHEV between 10:00 pm and 6:00 am. By 9:00 am only 

20 percent of households had their PHEV connected to the grid. This can be explained by 

the number of respondents in the Project that have full time jobs, and typically leave 

home in the morning to go to work. While two households charged during the day while 

at work, the other PHEVs plugged-in to the electrical grid during midday were due to 

retired individuals and teleworkers who typically were at home during the day. At 4:00 

pm, when households start to return home from work, vehicles begin to be plugged in, 

until 10:00 pm by which time the percentage of households who have plugged in their 

PHEV stabilizes again at about 70 percent. 

As Figure 18 represents an average from all participants’ weekdays during their last 

week, it is not a representation of actual daily behavior. Daily electricity availability 

varied within each household from day to day. Figure 19 represents the observed 

variability in when households plug in their PHEVs on weekdays, showing the low and 

high values for the percentage of vehicles plugged in for all weekdays by time of day. 

The bottom edge of the red area represents the low values observed at each point in time, 

and the top edge, the high value. For the time period between midnight and 6:00am, the 

lower values are predominantly due to the recharging behavior on Monday nights. 

The greatest difference—in excess of 30 percentage points—between low and high 

percentages of households plugging in their PHEV occurs during the early evening, and 

reflects the variability both 1) within and across households in when they plug in the 

vehicle in the evening, and 2) variation across different days of the week. The lower 
 47 

boundary of the electricity availability during the evening is largely defined by Friday 

when more people tended to plug in the PHEV later in the evening. 

Figure 18: Electricity Availability (Percent of PHEVs Plugged-in) and 

Instantaneous Power Demand by Time-of-Day (Watts), Weekday Average. 

Figure 19: Variability of Weekday Electricity Availability by Time of Day, 

Percent 
 48 

While the electricity availability tells us when the vehicles were connected to the grid and 

could recharge from the electric grid or discharge to the grid, it does not differentiate 

between the two. We discuss electricity demand for recharging next. The blue line in 

Figure 18 shows the average weekday instantaneous power demand by time of day for all 

34 Project households-to-date. Instantaneous power demand is derived by summing the 

power demand created for every day of the week by time of day for all participants’ last 

week, and averaging across all five weekdays to create an “average weekday.” Given 

driving and recharging behavior by the Project households, electricity demand to 

recharge their vehicles ramps up at 5:00pm and peaks just after 10:00pm. It declines 

steadily through the rest of the night and into the morning, reaching practically zero by 

5:00am. While there were several households that charged during the day at work, most 

of the demand to recharge these vehicles was between 9:00am and noon. 

As we did with electricity availability, we show the day-to-day variability in 

instantaneous power demand for a given time of day, i.e., we start to disaggregate the 

average to show the range of demand across weekdays. As Figure 20 shows, the most 

variability in time of day power demand occurs in the evenings between 5:00pm and 

midnight. The lower boundary of the power demand between 4:00pm and 8:00pm is a 

primarily a result of the increased probability of households plugging in the PHEV later 

in the evening on Fridays. The upper boundary is shaped by a higher percentage of 

people recharging earlier on Wednesday nights. Regardless of the absolute power level at 

5:00pm, there is a rapid increase in the instantaneous power demanded between 5:00pm 

and 6:00pm. 

By comparing electricity availability and instantaneous power demand in Figure 18, we 

see a picture of aggregate recharging behavior and, consequently, of grid impacts. In the 

absence of any signals, e.g., prices, or supporting systems, e.g., timers, on weekdays 

households tended to plug in their PHEVs in the early evening, usually upon arriving 

home, and to unplug them when they left home in the morning. This means that the 

period between 5:00pm one day and 9:00am the next morning on weekdays is the period 

with the highest average likeliness of a PHEV being plugged in. Instantaneous power 
 49 

demand increases rapidly starting at 5:00pm as more vehicles are plugged to the grid, 

especially if those vehicles plugged in earlier have not yet finished recharging. 

Figure 20: High and Low Weekday Instantaneous Power Demand, Watts 

While the prospect of rapid increases in electricity demand during peak hours is 

frightening to electricity providers as well as to energy and environmental analysts, it is 

clear from our observations that there is potential to shift electricity demand for these 

PHEVs from the early evenings, i.e., 5:00pm to 8:00pm, until after 10:00pm, since 

instantaneous power demand to recharge these vehicles declines rapidly after 10:00pm 

and all recharging is completed by 5:00am the following morning. 

Electricity Availability & Instantaneous Power Demand: Weekend Days 

Weekdays may provide routines to daily life, including vehicle travel: a daily commute, 

trips to school or daycare, or the stop at the grocery store before heading home. 

Weekends may lack these routines or have their own. Hence, driving and recharging 

behavior, access to a plug during the day and the time of day instantaneous power 
 50 

demand, may differ from weekdays. To track and account for these differences, we 

provide next an analysis of weekend days that parallels the analysis above for weekdays. 

Figure 21 shows the average percent of vehicles plugged in at a given time of day during 

weekends (in red, on the left axis) and instantaneous power summed across households 

and averaged across weekdays (in blue, on the right). Fewer PHEVs are plugged in 

during the weekend high availability period than during the weekday high availability 

period: about 55 percent of vehicles were plugged in between 11:00pm and 6:00am on 

weekends as compared to 70 percent between 10:00pm and 6:00am weekdays. Note also 

that the high availability period starts an hour later on weekend days than on weekdays. 

While electricity availability decreases toward and into the morning, it does so gradually 

and does not decline below 15 percent. The incidence of vehicles being plugged in again 

between 2:00pm and midnight increases less rapidly than on weekdays. Compared to 

weekday recharging, it appears as though some individuals, if they had access to an 

outlet, plugged in longer during the weekend. However, on average, not as many people 

plugged in their vehicles on weekend days compared to average weekdays. 

Figure 22 shows the low and high values for the percentage of vehicles plugged in during 

weekend days. While there appears to be little variability in the percentage of vehicles 

plugged in during the morning and afternoon, there is a greater difference between 

7:00pm and 12:00pm. The lower boundary is made up of those recharging events that 

occurred on a Saturday, with people tending to plug in later in the evening. Sunday 

recharging makes up the upper bound of the evening in the figure, where most vehicles 

had been plugged in by 8:00pm. The blank areas signify no difference between the high 

and low values. 

Figure 21 also shows the average instantaneous power demand incurred on all weekend 

days. As with weekday electricity demand, most actual electricity demand to recharge the 

vehicles occurred between 5:00pm and 2:00am during weekend days. However, it should 

be noted that there are significant differences in the total power required. On average, 

weekend electricity demand increased more slowly over the course of the evening. In 

general, this difference from weekdays is because during weekends the PHEVs are 
 51 

starting their recharging at a higher state of charge than on weekdays, and, thus, there is 

not as great a cumulative impact upon the power demanded. Essentially, as those vehicles 

plugged in later start recharging, their impact on the rate at which total power demand 

increases (summed across all households) is less than on weekdays, because other 

households’ vehicles which were plugged in earlier have already finished recharging. 

Figure 21: Electricity Availability (Percent of PHEVs Plugged-in) and 

Instantaneous Power Demand by Time-of-Day (Watts), Weekend Day 

Average. 

Figure 22: High and Low Electricity Availability by Time of Day: All 

Weekend Days 
 52 

Figure 23 shows the low and high instantaneous electricity demand for all weekend days. 

Unlike weekdays, the greatest difference is in the very early morning. The upper 

boundary for the evening electricity demand is due to the demand observed on Saturdays, 

when people generally charged later than on Sunday. During weekends, the PHEVs were, 

on average, plugged in until later in the morning, and recharging took place over a longer 

time period and at lower total energy demand during the evening. Since the PHEVs 

started recharging at a higher state of charge and the vehicles were plugged in over a 

longer period of time, instantaneous electricity demand increases more slowly over the 

course of the evening than was the case for weekdays. As with the case of weekday 

instantaneous power demand, it appears as though there is an opportunity to shift 

recharging of these PHEV-conversions by these households to present off-peak electricity 

demand periods. 

Figure 23: High and Low Weekend Days Instantaneous Power Demand, 

Watts 

Variation in Vehicle Use, Recharging, and CD-miles Across Households 

The recharging results presented so far focus on the recharging behavior summed and 

averaged across the participants. This hides the variation in 1) the frequency with which 
 53 

people recharged the PHEV, 2) the distances households drive per recharging interval, 

i.e., the distance driven between two recharging events, and 3) the percentage of total 

miles each household drove in CD mode. The participants varied in their experiences 

with the vehicle, in their concepts and appreciation of the value of recharging, and in 

their access to different recharging locations. These differences will be discussed in a 

following section on narratives in which we relay the households’ stories about their 

PHEV trials. For now, Figure 24 illustrates the overall variability in performance of the 

participants with regard to their average monthly (gasoline-only) fuel economy, the 

percentage of miles they drove in CD mode, and the overall distance they drove in the 

PHEV during their respective vehicle trials.18

Figure 24: Gasoline-only Fuel Economy by Percentage of Miles Driven in 

CD Mode, Weighted by Total Monthly PHEV (CD+CS) Distance 

 

18 The individual households identified in Figure 23 will be discussed in further detail throughout this and 

following sections. 

0

20

40

60

80

100

0% 20% 40% 60% 80% 100%

Miles Driven in CD Mode, Percent

Kermode Lakes Nancy Octavia All other Households
 54 

In Figure 24, each circle represents one household. The diameters of the circles are 

proportional to the total miles driven by that household in the PHEV over their trial 

period. The largest circle (“Nancy,” in the lower left) represents just over 3,000 miles of 

driving. That it also depicts the lowest percentage of miles in CD mode and nearly the 

worst gasoline-only fuel economy in the trial to date is indicative of several long, multiday tours away from home during which Nancy rarely recharged the PHEV-conversion. 

The basic conclusions to be drawn are that individuals varied greatly in their driving and 

recharging behaviors and, importantly, in the relationship between these two. A few 

households drove only 20 to 30 percent of their miles in CD mode—and for their 

additional use of electricity from the grid achieved overall gasoline-only fuel economy 

that is barely equal to the EPA fuel economy ratings of a conventional Prius (though, on 

average, they always outperformed their own driving of the PHEV-conversion in CS 

operation). On the other hand, a few households drove approximately 80 percent of their 

miles in CD mode and achieved monthly average gasoline-only fuel economy measures 

of approximately 70 mpg. A simple linear regression fit to the (distance-weighted) data is 

statistically better than simply fitting the mean of the mean average fuel economies (at α

< 0.01), but returns a modest adjusted R2

 = 0.55. The parameter estimated for the change 

in monthly mean mpg for a one-percentage point increase in the percent of miles driven 

in CD mode is 0.346: each percentage point increase in miles driven in CD mode leads 

to, on average, an increase of just over one-third mile per gallon in the monthly average 

fuel economy. While, as expected, a larger percentage of driving in CD mode is 

correlated with higher monthly mean fuel economy, there is much about the variation 

across households which is not accounted for by this simple model. 

Figure 24 shows the potential for drivers of these particular PHEV-conversions to 

achieve reductions in the gasoline-intensity of their daily mobility through changes in 

how they drive and recharge the vehicle, e.g., driving and recharging such that the miles 

in a recharging interval closely match the driver-vehicle’s CD range. Still, there is 

tremendous variability in how closely our participants’ behavior matches this technically 

ideal pattern that is not illustrated in Figure 24. We explore next the potential for 

differences in travel and recharging behavior to influence measures of gasoline and 
 55 

electricity use, both next through the more detailed examination of one household’s fuel 

economy and CD-mode data, and in an elaboration of three other households’ overall 

experience in the following section on narratives. 

The Kermodes19

Here we disaggregate the PHEV driving and recharging of one of our households into 

their PHEV recharging intervals. We choose this particular household not because we 

judge them to be representative of the all the Project households or generalizable to all 

households: we choose them because they illustrate the large effects that differences in 

travel and recharging behavior can make—even within one household. The Kermodes’ 

aggregate gasoline-only fuel economy and CD miles are shown in Figure 24 by the 

relatively large bubble centered on (22 percent CD miles, 49mpg). This makes them one 

of the “worst” performing households on one metric that is obvious and important to the 

Project households: (gasoline-only) fuel economy. We will show however that their 

aggregate performance masks a wide range of driving and recharging behaviors, signals 

to which the Kermodes responded, and possible summary measures to evaluate what 

difference it makes to the Kermodes to drive a PHEV vs. some other vehicle. 

We disaggregate their six-week experience with the PHEV-conversion in Figure 25. 

While also a bubble chart in which the sizes of most of the bubbles are proportional to 

miles driven, the bubbles for their existing mid-size sedan and compact SUV are not 

proportional to distance traveled but are sized only to make them easily perceptible in the 

figure. The Kermodes’ PHEV trial period lasted six weeks. For the first two weeks they 

drove the car with the PHEV conversion switched off, that is, they drove a slightly 

overweight but otherwise conventional Prius. During this time, they drove the vehicle 

480 miles, averaging 44.2 miles per gallon, and—by definition—their percentage of 

miles driven in CD mode was zero. The green circle labeled “HEV” centered at (0 

percent, 44.2mpg) in Figure 25 illustrates this performance. 

 

19 All names used throughout this report to refer to Project participants are pseudonyms. 
 56 

After two weeks, the PHEV conversion was switched in-line and the Kermodes drove the 

PHEV for four weeks. The aggregate measure of their four weeks driving the PHEV is 

shown by the large circle labeled “PHEV total” centered at (22 percent, 49mpg). This 

large circle is then disaggregated into the small circles (labeled “PHEV by recharge 

interval) representing each of the recharging intervals that make up their aggregate 

performance. Each blue bubble identifies a “recharging interval,” i.e., a new bubble is 

formed each time the car is plugged in. For each, we plot the gasoline-only fuel economy 

and the percentage of miles driven in CD mode, sized in proportion to the number of 

miles driven in that interval. We see that the variety of performances per recharging 

interval within this single household is greater than the variety of the monthly average 

performance across all the households shown in Figure 24. 

Figure 25: The Kermodes’ Distance-weighted Gasoline-only Fuel Economy 

by Percentage of Miles Driven in CD Mode per Recharging Interval 

0

20

40

60

80

100

-25% 0% 25% 50% 75% 100% 125%

Miles driven in CD mode, percent

Mid-sze Sedan Compact SUV HEV PHEV total PHEV by recharge interval
 57 

For their six-week PHEV trial, the Kermodes most often substituted the PHEVconversion—whether driven as an HEV or PHEV—for the mid-size sedan Ursula drives 

on a day-to-day basis. They recharged the vehicle at home every evening when they were 

in-town; when traveling out-of-town on multi-day tours, the vehicle was not recharged 

until their return home. 

Differences in their vehicle use and the relationship between their travel and recharging 

behavior explain the three groups of PHEV recharging interval bubbles in Figure 25. 

From left to right, the first group is made up of the four largest bubbles, all representing 

multi-day tours away from home during which the vehicle was not recharged. The only 

place the Kermodes charged was at home, with a single exception of a brief effort to 

recharge at a family member’s home during one of these long tours. For these tours, the 

PHEV substituted for the household’s luxury compact SUV rather than Ursula’s sedan. 

Second is a group of six recharge intervals that each represents a single day of driving 

around the Kermode’s home city that exceeds their achieved CD range: the Kermodes 

were able to drive up to 35 miles in CD mode in their around-town driving. Third is the 

group of several days during which 100 percent of miles were driven in CD mode—these 

were all days that Ursula drove the vehicle for her daily commute and errands, as well as 

for some occasional evening trips. 

Clearly the Kermodes’ driving and recharging behaviors and the resulting fuel economy 

measures differed widely throughout their four weeks of PHEV use. The questions thus 

arise: how representative are any of the three groups of recharging intervals? Or, for that 

matter how representative is their PHEV trial month as a whole? The long trips the 

Kermodes took during which they accumulated hundreds of miles without recharging are 

normal trips for them: the Kermodes did not simply set off on several road trips because 

we had given them a free car. In that sense, the entire month is representative of a month 

of the Kermodes’ travel—but not of every month. The Kermodes report the longest trips 

in their PHEV trial month are made typically twice a year. Based on the measures from 

the vehicle and the interviews of the Kermodes, an alternative month can be constructed 

in which the longest trips are replaced by other weekend travel days when the Kermodes 

stayed home. This constructed month yields new aggregate measures of 885 miles of 
 58 

PHEV travel, of which 48 percent of mile were traveled in CD mode, resulting in an 

aggregate, gasoline-only fuel economy average of 55 mpg. 

These two months of PHEV use—one as lived by the Kermodes and recorded by the onboard data systems and the other as constructed from that month based on the Kermodes’ 

interviews—are summarized in Table 4. The Kermodes’ lives over the course of a year 

can be represented by some combination of months like those shown in the table. The 

majority of months will be closer to the constructed month. But a couple of months a year 

will look similar to their actual PHEV trial month. The energy and environmental effects 

further depend on vehicle substitution within their household. In their actual PHEV trial 

month, the PHEV-conversion substituted for both their compact SUV for long trips and 

for their mid-size sedan for daily commutes. 

Table 4: Aggregate Measures of the Kermodes’ Actual and Constructed 

Months of PHEV Driving and Recharging 

Month Actual PHEV Constructed1

Miles 1,932 983 

Percent miles in CD 22 48 

Mean Monthly Gasoline-only Fuel 

Economy, mpg 

49 56 

Percent Difference from Kermodes’ 

mid-size sedan2

74 100 

Percent Difference from Kermodes’ 

compact SUV3

144 180 

Percent Difference from Kermodes’ 

non-PHEV Prius4

10 27 

1. The constructed month is based on the actual month, but substitutes measures of the Kermodes’ travel 

for weekends they remained home for a multi-day tour they made over one long weekend. 

2. The Kermodes estimated the fuel economy of their mid-size sedan to be 28mpg. 

3. The Kermodes estimated the fuel economy of their compact SUV to be 20mpg. 

4. Driving the PHEV-conversion for two weeks in CS operation, i.e., with the PHEV conversion taken offline, the Kermodes achieved an average of 44mpg. This period included one weekend trip out of town. 
 59 

It seems plausible then that, at the expense of the additional electricity consumed from 

the grid, the Kermodes would improve their gasoline-only fuel economy by as little as ten 

percent and as much as 180 percent depending on what is chosen as the comparative 

vehicle and travel.20 Compared to their own vehicles, driving this particular PHEV likely 

would achieve the claim of PHEV advocates to “double your fuel economy.” 

Unfortunately for their claim, advocates have been arguing that the doubling occurs 

relative to CS operation of a conventional Prius. The Kermodes are achieving nowhere 

near this increase: across the two months shown in Table 1 they achieve a 10 or 25 

percent improvement; even their best single recharge interval fuel economy (78mpg) 

approaches only an 80 percent increase in their CS fuel economy. (During one short allCD recharging interval, they had worse fuel economy than they achieved in CS driving, 

perhaps illustrating the sensitivity of this specific vehicle-conversion to the effects of cold 

starts and the operation of the emissions system for the ICE.) 

The point here is not that advocates are wrong or that PHEVs under perform (or over 

promise). Clearly, there is some PHEV in which the Kermodes could double their CS fuel 

economy while in CD mode. The point is that the efficacy of PHEVs is sensitive to not 

only technical design, but also driving and recharging behaviors and reference cases. 

The Overall Effects of Recharging on Energy Use 

One measure of the effects of recharging is the difference in (gasoline-only) fuel 

economy. We describe these results first as it is the measure used by most participants. 

Across the group, the mean CS fuel economy was 44.7mpg; the mean CD fuel economy 

was 67.1mpg. Thus, the group mean increase in CD vs. CS is 49 percent. These group 

measures mask tremendous variation across households. The distribution of households’ 

mean fuel economy improvements between CS and CD operation is shown in Figure 26 

the range is from 21 to 101 percent. However, improvements over 70 percent are 

 

20 As Ursula Kermode approaches retiring, they have already discussed reducing their vehicle holdings to 

one car. It is our judgment based on the interviews, that it is most likely they would keep the newer, more 

luxurious, but less fuel-economical, compact SUV. 
 60 

exceptions—90 percent of households had improvements less than 71 percent and the 

median improvement was 46 percent. 

Another measure that begins to integrate vehicle performance capabilities with owners’ 

driving and recharging behaviors is the percent of miles driven in CD mode. As the 

vehicle is fixed in this Project, differences across households are due to driving and 

recharging behaviors. 

Figure 26: Improvement in Gasoline-only Fuel Economy from CS to CD 

operation, percent 

The discussion above of (gasoline-only) miles per gallon reflects the use of this measure 

by most households as the goal and measure of their experience with the vehicle (though 

fuel economy was translated into other goals by different households, e.g., cost reduction 

and environmental benefit). A few households used other measures related to gasoline 

use, e.g., distance, cost per tank, or frequency of gasoline refueling. No household created 

for themselves an integrated assessment of both their gasoline and electricity use. 

0

1

2

3

4

5

6

0 10 20 30 40 50 60 70 80 90 100

Percent Improvement
 61 

However, such an integrated analysis is essential to the question of whether PHEVs 

deserve societal sanctions. The analysis presented here is preliminary and partial. It is 

preliminary because we do not expect that the full range and variety of the relationships 

between travel and recharging behavior on one hand and total energy use on the other 

have yet been observed among the Project participants’ to date. Further, this analysis is 

preliminary because only one particular PHEV is analyzed. The analysis is partial 

because it is not a life-cycle analysis; here we address only electricity out of the battery 

and gasoline out of the tank. Further, the analysis is partial because we address only the 

marginal difference that it makes that the Project households drove (and recharged, to the 

extent each did) a PHEV instead of an HEV. That is we compare their actual total energy 

use, i.e., gasoline plus electricity, during their PHEV trial to the amount of gasoline they 

would have used had they driven their entire PHEV trial without every recharging, i.e., 

entirely in CS operation. To illustrate relationships between driving, recharging, and 

energy use we plot the marginal percentage decrease in total gasoline (tank to wheels) 

plus electricity (battery to wheels) by the percent of their miles they drove in CD mode 

for their four-week PHEV trial in Figure 27. As in Figure 24, the size of each data point 

in Figure 27 is proportional to the total miles driven during each household’s trial (as an 

index of total energy use). 

The first point is that a comparison of Figures 24 and 27 shows that the households’ use 

of the simple measure of (gasoline-only) fuel economy is not qualitatively wrong. As the 

percent of miles driven in CD mode increases, fuel economy and total energy savings 

both increase. Whatever additional (dis)motivation, travel, or recharging would have 

resulted if households had created integrated representations of gasoline plus electricity 

use, cost, and emissions, the use of a simple measure of gasoline-intensity of their travel 

did not produce counter-productive outcomes. Figure 27 confirms that across the 

households, energy was being saved through the substitution of electricity for gasoline by 
 62 

recharging the PHEVs compared to what these households would have consumed had 

they not recharged the PHEVs—a conclusion that cannot be reached from Figure 24.21

The four households we’ve discussed in more detail are situated similarly in both figures. 

The relatively low percentage of CD driving of Nancy and the Kermodes—which we 

know was due to long, multi-day tours during which they did not recharge the PHEV—

yields low percentage energy savings from a large (compared to the other households) 

base. Octavia and the Lakes achieved much higher percent energy reductions but across 

much less travel, and thus a smaller energy base. They did so in part because of the much 

higher percentage of their travel they accomplished in CD mode—accomplished both 

because they recharged more often traveled fewer miles than Nancy and the Kermodes. 

Figure 27: Decrease in Households’ Total Energy (Gasoline plus Electricity) 

for their PHEV-conversion (as compared to an HEV) by Percent of Miles 

driven in CD Mode, percent. 















   	 
 




 
 ! "# "$
%&$

 

21 The household that shows an actual increase in energy use, i.e., a negative percentage decrease, despite a 

high percentage of miles driven in CD, had drivers with different driving styles and distances per trip. That 

is, one driver’s average CS fuel economy was as good or better than the other driver’s CD fuel economy. 
 63 

The four households in the furthest upper-right of Figure 27 provide interesting contrasts 

illustrating that driving fewer miles isn’t the only strategy to high percentage energy 

savings. The data for these four households are provided in the first four rows of Table 5. 

Two of the households drove only 500 to 600 miles during their four-weeks driving the 

PHEV—about three-fourths of these miles in CD mode. They achieved total energy 

savings of 19 and 18 percent compared to what they would have achieved had they never 

recharged. Because they traveled short total distances, they each displaced three to four 

gallons of gasoline, in part by consuming 56 to 64 KWh of electricity (out the battery). 

In contrast, the other two households who achieved the highest percentage energy 

savings—17 and 18 percent—drove over 1,500 miles during their PHEV trials. Their 

proportion of miles driven in CD mode is high: 71 to 81 percent. These two households 

each displaced nine to ten gallons of gasoline, in part by consuming about 141 KWh of 

electricity. How did these two households achieve similar percentage energy savings over 

many more miles than the previous two? The households that traveled longer distances 

achieved high percentages of CD mode by recharging multiple times per day. Both these 

households had one-way commutes that were about the distance of their realized CD 

range and both recharged at both home and work. In a sense, these two households 

achieved double (or more) their effective CD range daily; the households who traveled 

shorter distances but achieved similar percent savings did so because so many of their 

travel days were shorter than their realized CD range. 

The effects of the adaptations to a PHEV within a household can again be illustrated by 

the case of the Kermodes. Substituting the month we have constructed to simulate a 

month during which they do not take their long trips to southern California, but stay intown, their percent total energy displaced increases from the four percent calculated for 

their actual month to 14 percent. 

In aggregate across all the first households to participate in the Project, each driving the 

same version of a PHEV for four weeks, they drove over 33,000 miles. In doing so, and 

in recharging the PHEVs, they displaced 110 gallons of gasoline, at the expense of 2,066 

KWh of electricity. Each of the households displaced as little as one gallon of gasoline to 
 64 

as much as (almost) ten, at the cost of 19 to 141KWh respectively. A simple regression 

across all households returns an adjusted R2

 = 0.86 and an estimate that for each kilowatthour (out of the battery), on average, these households driving and recharging these 

PHEV-conversions displaced 0.065 gallons of gasoline (out of the tank) compared to the 

amount of gasoline they would have consumed had they not recharged. 

Table 5: Energy Use and Savings, sorted by Percent Decrease in Total 

PHEV Energy Use 

“Name” 

Total 

VMT 

Percent 

Miles in 

CD 

Gasoline 

Displaced 

(Gallons) 

Electricity 

(KWh) 

Total 

Energy 

(KWh) 

Percent 

decrease 

in Total 

 471 77% 3.43 55.85 69.60 19% 

 587 74% 4.13 63.60 87.65 18% 

 1,598 71% 9.76 141.08 216.20 18% 

 1,505 81% 8.93 141.30 185.92 17% 

Octavia 286 61% 1.58 25.16 32.62 13% 

 830 65% 4.35 77.10 82.14 13% 

Lake 716 74% 3.64 79.68 53.64 10% 

 902 55% 3.78 65.73 72.83 10% 

 1,739 58% 6.81 91.58 157.71 9% 

 1,772 62% 6.37 105.41 127.91 9% 

 824 65% 3.41 71.87 52.87 8% 

 1,275 50% 4.27 83.04 73.23 8% 

 1,111 71% 4.37 92.61 67.61 8% 

 1,538 36% 4.56 85.76 81.36 7% 

 1,043 32% 3.06 50.40 61.66 7% 

 1,369 42% 3.56 62.61 67.82 6% 

 1,639 50% 4.52 89.22 76.36 6% 

 743 68% 3.17 83.90 32.23 6% 

 1,526 43% 4.06 78.66 70.05 6% 

 1,687 43% 4.20 73.70 80.26 6% 

Kermode 1,932 22% 3.33 58.57 63.32 4% 

 568 26% 1.21 24.08 20.18 3% 

 944 57% 2.54 71.38 21.58 3% 

 738 19% 1.09 18.79 21.18 3% 

Nancy 3,040 17% 2.77 67.08 34.55 1% 

 1,372 27% 1.38 41.20 9.17 1% 

Total 33,422 49% 110.10 2,066.40 1,965.91 
 65 

Recharging Conclusions 

The households in this Project were selected in part because of their capability to 

recharge a PHEV at home. Further, they are all driving one specific incarnation of what a 

PHEV can be. For these reasons, and because of the probable correlations between PHEV 

performance capabilities and driving and recharging behaviors, the specific numerical 

results of this section should be interpreted with appropriate caution. 

That said, the households participating in this Project are, on average, plugging-in these 

PHEV conversions about once per day, and do so more often on weekdays than weekend 

days. There is large variation though even in the means across households—from zero to 

2.6 times per weekday and zero to 1.5 times per weekend day. The higher frequency of 

plugging-in on weekdays is associated with 1) some incidence of recharging at work on 

weekdays, and 2) recharging at home during the day by retired households. Overall 

frequency of plugging-in on weekend days is lower not only because there is no 

workplace recharging taking place, but because the PHEVs are more likely to be away 

from home, and thus the primary or sole recharging location. 

Comparing electricity availability and instantaneous power demand provides a picture of 

aggregate recharging behavior and potential for electricity grid impacts for weekdays and 

weekend days, illustrating both when these vehicles could have been recharged and when 

recharging actually occurred. In general, most households plugged in their vehicles after 

4:00pm on weekdays and left them plugged in until 6:00am. While the electricity demand 

from vehicles being plugged in between 5:00 and 6:00pm creates a rapid increase in grid 

electricity demand, the differences between the “availability” and “demand” curves show 

there is opportunity to shift recharging to presently existing off-peak electricity demand 

periods. Compared to weekdays, weekends present even greater opportunity to time-shift 

grid power for the vehicles since 1) fewer are plugged in, 2) those that are plugged in 

require less electricity to fully recharge, and 3) those that are plugged in tend to remain 

plugged in longer into the next morning. Furthermore, there are differences in 

opportunities to use PHEVs as “sinks” for excess electricity, based on the differences in 

how many vehicles are plugged in between weekdays and weekend days. 
 66 

While the electricity availability and instantaneous power demand characterized by this 

report are representations of what happened across the Project households’ PHEV trials, 

it is important to emphasize that individual household charging behavior, vehicle use, and 

vehicle performance varied across days, recharging intervals, and trips. Essentially, while 

we have accurately represented households’ last week or month of driving the PHEVconversion, that record of actual driving during the PHEV trial may not have been 

representative of every week or month of a household’s life. In an effort to demonstrate 

the different ways households could plausibly use these vehicles, we disaggregated the 

real month PHEV trial of the Kermode family and offered an alternate month based on 

their interview and vehicle data. The two months—the month as measured including 

multiple, away-from-home weekend tours and a constructed month that substitutes local 

weekend travel for the longest of these tours—provide descriptions within which most of 

the Kermodes’ vehicle driving and recharging will fall. Depending on which month and 

which comparative vehicle(s) one references, the effect on the gasoline-intensity of the 

Kermodes’ travel is bounded by estimates of ten to 180 percent. Further, the marginal 

effect of recharging on their total energy displaced by driving and recharging the PHEV 

ranges from four percent in their actual month of using the PHEV to 14 percent in a 

month plausibly constructed to represent other months of their life (keeping in mind their 

actual month with the PHEV does represent some months of their lives). 

The total energy savings and gasoline (tank-to-wheels) displaced by electricity (batteryto-wheels) are modest in aggregate and highly variable across households. Those 

households who are closely able to match their travel to (multiples of) their achieved CD 

range of these PHEV conversions are able to achieve much higher percent of their travel 

in CD mode and thus greater percentage total energy (gasoline plus electricity) reductions 

through the substitution of electricity for gasoline. These households achieve higher 

percentages of CD mode driving because either, their common daily travel is less than 

their achieved CD range or they had access to away-from-home (and in this case, 

workplace) recharging so that they recharged multiple times per day. 
 67 

3C. PROJECT RESULTS: NARRATIVES

Narrative Analysis: What, why and how? 

This section highlights the importance of talking to consumers and the value in hearing 

their stories. We have two purposes in employing narrative: synthesis and analysis. First, 

we have a tremendous amount of disparate information about each household. Narrative 

provides a framework to organize, analyze, and report all these data: quantitative and 

qualitative; numeric and text; researcher observations, transcripts of oral interviews, online questionnaire responses, and vehicle and recharging data. Second, the purpose of 

narratives is to explain, to provide coherence, to show causality; individual datum record 

what happened; narratives tell us why. 

What is a Narrative? 

At its most basic level, we use narrative as a description of a story by a researcher 

(Berger and Quinney, 2005). Generally, narratives are produced in conversation. 

However, the data to construct narratives have also been collected through conversational 

interviews and field notes based on observations (Lieblich et al. 1998). For the Project, 

each household’s narrative was compiled from multiple in-person interviews, enhanced 

by field notes from the researchers, as well as data from the questionnaires completed by 

each household at the start and end of their PHEV demonstration period and quantitative 

measures of driving and recharging reported by the data systems onboard the vehicles. 

Our role as researchers is to tell the households’ stories of their month with a PHEV. 

“Stories provide coherence and continuity to one’s experience and have a 

central role in our communication with others...Stories imitate life and 

present an inner reality to the outside world; at the same time, however, 

they shape and construct the narrator’s personality and reality. The story 

is one’s identity...We know or discover ourselves, and reveal ourselves 

to others, by the stories we tell.” [Emphasis in the original.] (Lieblich et 

al. 1998) 

Narratives allow researchers to understand people’s beliefs and the meanings behind their 

actions by creating a stage for people to tell their story and outline who they are. Lieblich 

et al. (1998) states that a narrative researcher does not take the story as being a complete 
 68 

and accurate representation of reality; instead, meaning must be drawn from the story that 

was told. 

The criteria of what constitutes a narrative vary, though there are commonalities. 

Reissman (1993) states that a narrative must tell a story and have a clear beginning and 

end. The narrative takes chronological events and uncovers the meanings of what came 

before and what might come in the future; in essence, there is a plot, and the narrative has 

a purpose (Berger and Quinney, 2005). A narrative, without a plot is not an accurate 

representation of what happened. E.M Forster offers an example, “The king died, and 

then the queen died.” (Cited in Herman and Vervaeck, 2005). This is a chronology of 

events, but not a narrative. Only when plot is added does the story represent what 

transpired; in Forster’s example, “The king died and then the queen died of grief.” The 

queen dieing of grief indicates causality, a plot emerges, and a narrative is formed. 

Narratives are interpretive (Reissman, 1993) and the stories that are used for the 

construction of narratives are subjective (Lieblich et al. 1998). Reissman (1993) explains 

meaning is collaboratively produced by the teller, analyst, and reader and may vary from 

person to person. 

“A narrative never provides a perfect copy of the reality constituting its 

subject. A person who narrates what has happened to him will always 

summarize, expand, embellish, and leave out certain aspects of his 

experience. Since a narrative text is restricted to language, it will never 

show reality directly.” (Herman and Vervaeck, 2005) 

In the present case of this Project, the researchers are responsible for representing the 

participant as accurately as possible through the process of interpretation because it is in 

interpreting the narrative that its’ meaning is derived. Without interpretation, the 

narrative would be based solely on the participant’s version of reality. 

Writing the narrative is an essential step in the research process because it takes 

chronological events and arranges them in a way to tell a story, complete with a 

beginning, middle, and end, as well as a plot. Berger and Quinney (2005) explain that 

having people tell their own stories in the form of an interview is a unique opportunity as 

story telling extends the reality of our experiences: 
 69 

 “Stories are ways not merely of telling others about ourselves but of 

constructing our identities, of finding purpose and meaning in our 

lives...In the telling we remember, we rework, and reimagine the past, 

reflect back upon ourselves, and entertain what we have and could 

become.” 

Like all forms of data collection, narratives have limitations. Because researchers do not 

have direct access to a person’s experiences they must deal with ambiguous 

representations that do not allow for the purported neutrality and objectivity of 

quantitative methods: a researcher cannot represent a participant’s story without 

interpreting it. As Reissman (1993) says, 

“Meaning is ambiguous because it arises out of a process of interaction 

between people: self, teller, listener, recorder, analyst, and reader. 

Although the goal may be to tell the whole truth, our narratives about 

others’ narratives are our worldly creations...All we have is talk and 

texts that represent reality partially, selectively, and imperfectly.” 

Along with this co-construction between participant and researcher of reality comes 

another limitation: the co-construction of reality allows for the avoidance of some facts 

(Schram and Neisser, 1997). Writing a narrative takes caution and a focus on details in 

order to maintain the integrity of the participant’s story without injecting the researcher’s 

own agenda or biases.

The Value of Narratives 

Narratives are valuable to the research process for several reasons. According to 

Reissman (1993), having participants tell their life stories allows them to use human 

agency and imagination to determine what to include, how events are emplotted, and 

what they mean. Similarly, Lieblich et al. (1998) explains that the life story creates and 

transmits a person’s individual meaning in addition to cultural meanings. This allows the 

researcher to understand what the participant believes as well as what their culture 

prescribes. 

A personal experience can be too narrow to highlight important social debates; the 

personal experience becomes compelling when multiple people duplicate it, therefore, if 

several participants cite the same issues in their narratives then these should be looked at 
 70 

closely (Berger and Quinney, 2005). This is largely important to policy makers. Schram 

and Neisser (1997) argue that narratives help realize political space and those in the 

political sphere use stories to engage in political change. For example, urban legends 

about international terrorism give voice to anxiety about personal control, which in turn 

legitimates forms of state action and surveillance. Stories lead to political action; 

narratives can be used to stimulate change. It is crucial to understand people’s stories in 

order to understand what is happening in society as a whole. A compelling story has the 

ability to connect personal experiences to public narratives, essentially allowing society 

to speak through each individual (Berger and Quinney, 2005). This is highly valuable 

when dealing with public policy and cultural change because it can allow the researcher 

to foresee the reaction of the general population and suggest alterations to attempt to 

affect the speed and direction of change. 

How do We Create Household Narratives? 

Narrative creation begins with the household interviews. Interview protocols, i.e., an 

outline of topics to be included in the interview. These topics come from the research 

questions for this Project. The protocols use open-ended questions to allow the 

respondents the freedom to go in directions they choose. The interviews are recorded and 

the mid-term and final interviews are transcribed.22 Referring back to both, the interviews 

are coded by a researcher reading through the entire record several times to locate 

patterns or reoccurring themes. A list is made of all the themes and they are put into subcategories determined by the scope of the study. As Lieblich et al. (1998) explain, a 

separate read-through is done for each theme and notes are based on the researcher’s 

initial conclusions. Analysis is drawn from these notes, an overall picture of the 

participant’s story is created, and a narrative is written. Additional material is brought in 

from the on-line questionnaires, especially as one of the topics for the final interview is to 

review the PHEV designs created by households in the final questionnaire. Further, as 

 

22 The initial interviews that are part of the vehicle drop-off procedures are not transcribed in-full primarily 

because they largely consist the formalities of completing paperwork, checking on the intended parking and 

charging location for the vehicle, and explaining the vehicle operation and research process. That is, too 

much of these initial “interviews” consist of the researchers talking, not the households, to warrant the 

transcription of the audio recordings. The recordings are reviewed and relevant passages are noted. 
 71 

was done for the Kermodes in the previous section on recharging, data from the vehicle is 

analyzed and incorporated in the story about each household’s month with a PHEV.

Illustrative Stories from Three Households 

There are three major types of household narratives that have emerged from the first 34 

households to participate in the Project. The first type consists of people who understood 

the PHEV technology before they started their demonstration, represented here by Rick 

and Samantha Lake.23, 24 The second type did not understand the PHEV technology—

even after their PHEV trial period, represented by Nancy. The third type started out their 

PHEV trial not understanding the PHEV technology but developed a better understanding 

over the course of their trial, represented by Octavia. Brief introductions to these three 

households’ narratives are presented here; fuller versions are included in Appendix F. 

(They are also discussed in the previous recharging section.) 

The Lakes 

Rick and Samantha Lake are married with two young children and live in a large house in 

a gated community. Rick drives a 2002 Honda Accord, mostly to commute to work; 

Samantha drives a 2004 Honda Odyssey to run errands, shuttle children, and generally 

run their household. The Odyssey is also used for longer family road trips. They 

substitute the PHEV for the Accord. 

Prior to the trial, Rick and Samantha were fairly familiar with electric-drive vehicles, 

especially compared to other households in the study. They knew neighbors that drove 

neighborhood EVs, such as the GEM, and Rick had ridden in a hybrid Civic. Rick had 

seen a news clip featuring UC Davis PHEV Research Center Director, Tom Turrentine, 

showing off the battery of the PHEV-conversion. Rick recalled the statement that a driver 

could get 100 mpg for the first 40 miles, so he was “shooting for 100 mpg.” 

 

23 “Understanding” is a relative concept in this context. No household had a sophisticated, expert 

understanding of PHEVs. The group referred to here understood that the car ran on both gasoline and 

electricity, that it could be plugged into the electrical grid. 

24 As noted in the previous section, all names used throughout this report to refer to participants are 

pseudonyms. 
 72 

The Lakes enjoyed driving the PHEV. Rick drove it for his 19-mile roundtrip commutes 

most days. He said, “...for day-to-day commute, it’s great” and fit into their lifestyle 

“fairly seamlessly.” Rick was “expecting high mileage and it delivered.” Rick’s 

assessment of the PHEV was at least partially related to his perceptions of pure EVs, “for 

me it was the combination of having the gas and electric assist, it made it easier to 

integrate into our life than pure electric, because it had that gas component you never 

really worried.” Rick was frustrated that the engine would come on even during short 

trips, when “it’s burning gas, and I don’t need it...just a half mile...why doesn’t it just 

run on electricity?” Every night Rick plugged in the PHEV and unplugged it every 

morning. Sometimes he would plug it in during the afternoon if they were going to use it 

at night. Samantha drove the car only five or six times, mostly for errands or taking the 

children to school. 

Rick liked to monitor how he was doing by watching his fuel economy as well as the 

Energy Monitor screen in the vehicle to see if the [supplemental conversion] battery was 

being used.25,26 He would experiment with different behaviors, “I’d gas it and watch 

it...put my foot off the throttle and watch it...out of curiosity to see how my actions 

affected things...air conditioner, no air conditioner.” Rick was also motivated by his goal 

of achieving 100 mpg or higher, which he successfully reached several times according to 

data from the vehicle. 

In contrast to Rick’s initial focus on the energy instrumentation, Samantha said, “I’m the 

opposite, oblivious...just driving...I pay attention to the road mainly.” She figured that 

the PHEV was “gonna do what it was gonna do.” Once the Lakes were given access to 

their data on the V2Green website, Rick visited the website often and seemed to integrate 

the provided information into his assessment of the vehicle. 

 

25 Throughout these discussions of the households, the phrase “fuel economy” refers only to gasoline use. 

This corresponds to the households’ understanding and use of language regarding these vehicles. 

26 Detailed descriptions of the in-vehicle instrumentation and the website providing further information 

about the vehicles’ performance are given in the next section on interfaces and information. 
 73 

The Lakes seemed especially interested in two topics relating to the PHEV: the idea of a 

payback period and helping the environment. When discussing whether he would 

purchase a PHEV, Rick said, “I would do a little cost-benefit analysis...you can kick in a 

little premium, maybe a 10% premium just to go green or do your part for the 

environment to be a good citizen.” When asked specifically what he liked about the 

PHEV, Rick included the potential to reduce CO2 emissions through reduced gasoline 

use, at least “in theory.” He further states, “I don’t know whether or not it really reduces 

pollution...but it’s nice to think it does...nice to have the perception that you are doing 

something to help out.” Rick’s uncertainty seems to stem from a lack of information 

about the pollution from electricity generation and battery production. 

Yet despite his repeated claims to subjecting their PHEV choice to a payback analysis, it 

is clear that Rick did not subject his PHEV design with 10 miles AER (in the design 

games in the final questionnaire) to such an analysis.27 Despite his repeated stories and 

claims, and despite responding to Samantha’s challenge in the final interview about 

whether CS fuel economy would payoff,28 the PHEV capability Rick has decided he 

wants—to be able to drive back and forth between home and work using only 

electricity—is something he is willing to do without calculating costs and benefits, by 

shifting his travel times, by attempting to get a plug installed, and even by using a plug he 

has previously deemed unsuitable (because it is located between elevators). 

Samantha brought in more global resource concerns. She described how, when gas prices 

recently went up, they saw more television shows talking about natural resources: “...how 

much we have and why, and the other developing countries like India and China who are 

now playing a bigger role in wanting the resources...I think we need to figure out ways to 

 

27 The households complete the final questionnaire before the final interview. In the final interview selected 

questions from all the questionnaires are reviewed with the household. These include the PHEV designs the 

household creates. This allows the researchers to explore with the households why they created the designs 

they did, and to have the kind of exchange with the Lakes described here. 

28 Rick designed his PHEV in the final questionnaire without consulting Samantha. In the final interview, 

she challenged his design, which did not include CS fuel economy improvements. She felt CS fuel 

economy improvements would be “worth it.” Rick got up from the interview, retrieved his calculator, 

returned, made some quick calculations, and concurred with Samantha. The interviewers did not press him 

to share his calculations. 
 74 

make sure that globally everyone gets what they need...we’ve got to pass on the world to 

the next generation.” 

Overall, the Lakes enjoyed using the PHEV. When asked if they would consider 

purchasing a PHEV Samantha said, “The increased fuel economy sounds good, to save 

money and contribute to the solution of global resource problems. But we are not willing 

to compromise much on functionality, the vehicle would have to fit into our family’s 

lifestyle, such as storing groceries and allowing long road trips.” 

Nancy 

Nancy is a single, retired grandmother who lives in an older, modestly sized, attached 

home. She is the primary caregiver for her young grandson. As a caregiver with a single 

income, Nancy admittedly watches her money closely and is always looking to get the 

most for it. She substituted the PHEV completely for her only vehicle, a 1991 Toyota 

Camry with 253,000 miles. 

Nancy did not know what to expect from the PHEV. Having no experience with any 

hybrid vehicle, she seemed to struggle with the concept of how the car worked and how it 

was different from a conventional Prius. However, she was quick to understand that using 

electricity could save her money on gasoline. 

Nancy did not notice a difference between when the vehicle was in CD or CS operation. 

Nor was she aware of where the energy to move the vehicle was coming from. She said, 

“I don’t know when it’s using gas...or electricity. I can’t tell. Am I supposed to be able to 

tell? Can you tell?” Nancy knew that by using electricity she got “good mileage.” She 

said, “I’d rather use the battery, then you don’t have to fill up as much. The gas will last 

longer.” Nancy explained that she had a feeling she was getting good mileage based on 

how far she could travel on $20.00 worth of gas, and that as a consumer she generally has 

an instinct for good value: she “just knows” when she is getting her money’s worth or a 

good deal. 

Nancy claimed that looking at the fuel consumption and energy monitor displays did not 

influence her driving. She saw the instantaneous mpg reading, but the numbers “kept 
 75 

changing from 17 to 99 mpg” and she found it too much to process. She was also 

confused about what the arrows meant on the Energy Monitor screen, or what the display 

was telling her. She said, “I try to watch (the screen)...I thought I was getting it...but I 

think I am just confused.” 

Nancy found charging the PHEV to be very easy, both at home and on a trip to Southern 

California. When at her own home she only charged at night and was adamant that this 

was the way to go, calling herself a “nighttime charging gal.” Nancy charged the vehicle 

18 times during her four weeks with the PHEV, usually plugging in between 8:00 pm and 

12:00 am and unplugging the next day before a trip. She seemed to fall into a charging 

routine with the vehicle even though she could not tell when the battery was discharged. 

Despite her confusion about how the car worked, Nancy enjoyed driving the PHEV. She 

especially enjoyed showing off the vehicle to her friends and family during a trip to 

Southern California. Overall, Nancy concluded, “I never would have picked that car, but 

after driving it for a month, it just feels right. I really would like to buy one with a plug if 

I could afford it, because I really feel like I am getting the most for my money when I use 

the electricity.” 

Octavia 

Octavia is a middle-aged woman who lives with her retired mother in an attached home, 

works as a librarian, and drives a new Honda Civic. She was not familiar with any hybrid 

vehicle technologies prior to this study. She completely substituted the PHEV for her 

Honda Civic. 

Octavia said the car performed “great” without any “compromise” for the added benefits 

of fuel economy. She felt the PHEV was quiet and smooth, although she did occasionally 

feel a “lurch” when the engine kicked in. While driving, Octavia focused on the fuel 

economy information in the vehicle; she found the battery state of charge indicators to be 

confusing. She was surprised by the “phenomenal” increase in gas mileage relative to her 

Honda Civic and said the accompanying reductions in carbon emissions were “even 

better.” She linked gas savings with energy independence and reducing environmental 
 76 

impacts. Octavia said that in the world today, “we have people dying...corruption and big 

business...due to the whole dependence on oil...we are in trouble...we can’t keep going 

this way.” She felt that the PHEV gauges would help people make a stronger connection 

between their personal actions and global problems. 

Octavia greatly changed her recharging behavior over the course of her four-week trial. 

During the first two weeks she was unsure how to judge the battery’s state of charge and 

would plug-in for 3-5 hours every other day or so. She was just “guessing” and did not 

follow a consistent pattern. After being introduced to the V2Green website, she saw that 

there was strong potential for her to improve her fuel economy. She felt her 

understanding of the car improved further a week later when she read the PHEV “buyer’s 

guide” in preparation for her PHEV design exercises in her final questionnaire. With this 

information she said, “Now I get it...I’m not charging it enough...I’m (switching) to 

gasoline half way through my day...I’m not utilizing the battery component...I need to 

start at 100% every day.” The handout helped her pull together the information of how 

long it took to recharge the vehicle to maximize her gasoline savings. 

At the close of her PHEV trial, Octavia really liked the car and regretted having just 

bought a new Honda Civic without at least test-driving a hybrid. In the future she would 

consider PHEV options, but would have to think further about the specific attributes she 

would like, such as all-electric vs. blended operation. She also noted that for a longerterm scenario she would likely seek out additional recharge opportunities other than her 

home, and potentially modify her driving behavior to further reduce gasoline usage. 

Themes from Households’ Narratives 

Here, we use elements from these three narratives to illustrate the themes that emerge 

from narratives of the first 34 households. Supporting material from other household’s 

narratives will also be included. These themes relate to driving and recharging behaviors, 

confusion about PHEVs, and the issue of whether and how households think about 

payback periods when evaluating whether a PHEV is a good idea. 
 77 

Changing Driving Behavior 

Some households discussed a change in their driving behavior, specifically accelerations, 

top speed, and coasting. Like Rick Lake, these drivers stated that seeing their 

instantaneous fuel economy affected how they drove because they could determine what 

behaviors led to a drop or rise in mpg. Rick’s monitoring and experimentation, “I’d gas it 

and watch it...” seemed to be a fairly common behavior among those households who 

watched the in-vehicle screens. Another participant discussed a change in his behavior, 

“...it helps you watch your driving habits, like not driving too fast...if I’m going to point 

A and point B I don’t want to drive too fast because...you’ll be using more gas. If I slow 

down...then you’re using both gas and electric...” The instantaneous fuel economy 

reading on the Energy Monitor screen created an opportunity for nearly constant 

monitoring of driving behavior for some participants. These drivers were aware of how 

their actions were impacting the performance of the car and their overall fuel economy. 

Others, and most so far are women, said they drove the PHEV like their normal car, and 

did not continuously monitor their fuel economy. Recall that in contrast to Rick’s initial 

focus on the energy-use instrumentation, his wife Samantha stated: “I’m the opposite: 

oblivious...just driving....” She reasons that because she is driving fast she has “got to 

pay attention [to the road],” and thinks that Rick looks at the Energy Monitor too much. 

She and many like her did not make the connection that their behavior impacted the fuel 

economy of the vehicle. 

Several people, especially those who constantly monitored their fuel economy, saw 

driving as a test or a game and tried to attain a certain mpg or maximize the distance over 

which the supplemental battery charge would last. A few households were able to enact a 

friendly competition between household drivers to see who could get the highest fuel 

economy. Rick Lake used the information from V2Green to (playfully) compare his fuel 

economy with Samantha’s: 

Rick: “When I drive it’s about 75 [mpg], when [Samantha] drives 

it’s about 50...I looked on the Internet (laughs). 

Samantha: “...what does that mean—highway vs. city? 
 78 

Rick: “...could be...or more aggressive accelerations...I coast a 

lot. 

Samantha: “...I’m in a rush to get somewhere... 

Rick: “...right, nobody passes mommy (laughs).” 

Rick Lake used the vehicle information reported and summarized on the website to 

determine whether he or Samantha was the more economical driver, but she would not 

engage in a competition. 

Other households though were able to use their energy information to stimulate a 

competitive game between drivers in a household. When asked if they looked at the 

average miles per gallon during the trial, one household responded, “...yeah, I looked at 

that, and so my husband would have a contest, okay, let’s see who had the best.” It was 

not uncommon for households with more than one participating driver to engage in a 

friendly competition to see who could get the higher fuel economy. This seemed to turn 

driving the PHEV into a game and allowed the households to engage the car in a way 

they had not prior vehicles. 

Recharging Habits and Etiquette 

Most households spoke of recharging becoming part of their daily routine, like 

recharging a cell phone or feeding the dog. Some, like Nancy, referred to it as an 

additional daily chore. The majority of participants said plugging-in was easy and not a 

hassle, except for the awkward extension cord—many observed that a retractable cord 

would be a welcome change. Most people recharged at home because of the time needed 

to recharge the battery, availability of an electrical outlet, and safety of the car (and cord). 

Most stated that recharging at night was ideal because they could plug-in the car when 

they got home and un-plug it in the morning before heading to work. Several, including 

the Lakes, Nancy, and Octavia, were concerned about plugging in their car if it was 

parked outside of their garage for fear of a tripping hazard or someone stealing the cord. 

Some looked for recharging at local malls, job sites, or during out-of-town trips; none 

found it easy to locate an appropriate outlet. They report no etiquette for recharging 

behavior, so they were unsure if asking to plug in would be rude or presumptuous. One 
 79 

participant, Casper, who worked in construction, discussed his hesitancy to recharge at a 

work site he had to visit, “...it didn’t seem like it would be appropriate to just pull right 

in there and plug into their power.” Without making a calculation, Casper rationalized 

that normally plugging in at a job site would not be a problem because, “...the amount of 

energy that I’m going to take from him [the contractor who pays the electricity bill] 

doesn’t even equal six guys with power saws cutting lumber...all day.” However, several 

times during his interviews, Casper wondered whether it would be appropriate or not to 

plug in at a variety of other places. 

Several participants specifically related that they did not ask to recharge at the houses of 

friends or family because they were unsure of the etiquette, while others saw recharging 

away from home as an opportunity to show off the car and explain the technology. A few 

of the households said they would request an outlet be installed at their work location 

and/or around their community if they were to own a PHEV. 

One issue of particular importance to the larger social and policy discourse about PHEVs 

is recharging frequency. By the end of their PHEV trials, if the participants understood 

how to maximize the use of the supplemental battery, they were recharging every night. 

Those who did not understand battery SOC, or PHEV technology in general, did not 

necessarily recharge nightly or, in some households, in any apparent pattern. 

When asked about recharging, most participants discussed the actual act of plugging in 

the cord but not the frequency with which they recharged. Despite several households 

questioning us about how often to recharge when the PHEV was first delivered to them, it 

appears that recharging either 1) quickly became a daily routine or chore—irrespective of 

the level of understanding of why they would plug the car into the grid—or 2) that 

differences in the performance of the PHEV in CD and CS mode were not adequately 

represented to some households for them to understand why and when to recharge the 

car. We will return to this latter possibility in the section on interfaces and information. 
 80 

Confusion 

As might be expected from a group of people in which few had prior experience with 

electric-drive vehicles, many respondents were initially confused by the idea of a PHEV. 

Whether this confusion remained or was replaced by a more grounded understanding 

over the course of their trial month distinguishes some households from others. For 

example, Nancy and a few other households knew recharging helps increase fuel-only 

economy but did not understand how. Nancy did not notice a difference between when 

the vehicle was in CD or CS operation. Nor was she aware of where the energy to move 

the vehicle was coming from. Nancy was arguably the most confused participant, but 

many households were unfamiliar and uncomfortable with the PHEV technology—some 

even after they had spent a month with the vehicle. 

Most of the households were confused about the state of charge of the battery. The 

battery SOC indicator on the Energy Monitor screen will flicker and then switch between 

two colors as the vehicle transitions from CD to CS operation. This bit of feedback was 

missed by most people and understood by few. Some thought they could determine when 

the supplemental battery expired based on the relatively large drop in fuel economy when 

switching from CD to CD operation. Drivers were more likely to notice this change in 

fuel economy if it happened to coincide with some regular set of trips. For example, one 

household determined that if he paid attention to moderating his driving, his one-way 

commute trip was just about as long as he could keep the car in CD mode. 

But many drivers had no idea. This—combined with incorrect mental models of 

batteries—caused some participants, like Octavia initially, to recharge less frequently 

than they would have if they had known how to determine the state of charge of the 

battery and if they had understood what the benefits might be. Octavia cited the example 

of her cellular phone—so long as it had some charge, she derived full value from the 

phone calls she made or received on it. Many households voiced a desire to have a clear 

reading of the state of charge of the battery in order to determine how far they could 

travel using the battery and when it should be recharged. 
 81 

Most found the in-vehicle instrumentation to be poorly designed, but only a few did not 

understand the information being displayed. Nancy was one who never seemed to learn 

what the car might have been trying to tell, rather she felt overwhelmed by the PHEV 

display screen. She saw the instantaneous mpg reading, but found it too much to process. 

She was also confused about what the arrows meant on the Energy Monitor, and about 

what the display was telling her. She said, “I try to watch [the screen]...I thought I was 

getting it...but I think I am just confused.” 

Payback 

Many households discussed using some form of a cost-benefit analysis to determine 

whether the PHEV was “worth it.” Most of these households discussed simple payback 

analysis comparing differences between a higher purchase price and lower operating cost. 

A few households discussed more sophisticated net present value calculations. Despite 

these discussions, no households appear to have completed either simple payback or net 

present value calculations. Most households made mistakes in describing how to make 

such calculations and demonstrated they did not know the values of the costs and benefits 

that would enter into such a calculation. 

Throughout the trial Rick Lake repeatedly discussed the idea of payback and whether the 

PHEV was “worth it.” However, during the design games prior to the final interview he 

used no such calculation to determine his PHEV designs. When asked if he performed a 

payback calculation he admitted that he had not; he did do one during the final interview 

on a PHEV design that Samantha suggested as an alternative to his. That Rick had not 

done this calculation for his design was shocking to the researchers because he (and 

Samantha) had repeatedly emphasized how important such calculations are to him, even 

telling a story about a (friendly) argument between Rick and his brother-in-law regarding 

the payback time for an on-demand water heater. 

Even for those who discussed payback, existing prices were not always the preferred 

values. As an adjustment to such calculations, many households factored in the 

environment and “doing their part,” for example Rick and Samantha Lake who stated, 
 82 

“you throw in another 10 percent for the environment.” They saw helping reduce 

environmental concerns as a benefit and worth the cost of the additional battery. 

In contrast, other people made more intuitive evaluations. For Octavia, using less gas 

“was a great feeling” because it “has got be a good thing.” She linked gas savings with 

energy independence and reducing environmental impacts. Octavia felt that the PHEV 

instrumentation would help people make a stronger connection between their personal 

actions and such global problems. For her, this awareness was a large benefit to driving a 

PHEV. She figured that most current HEV buyers were driven by financial motives, 

whereas if she were to buy an HEV, it would be for environmental reasons. She believed 

that climate change is a real, human-caused problem that, along with air pollution and the 

nation’s dependence on foreign oil, requires urgent action. She sees owning a PHEV as 

part of the solution for these problems. 

Narrative Conclusions 

This form of data collection, analysis, and synthesis allows the researchers, policymakers, 

and manufacturers to understand people’s beliefs and the motivation behind their actions. 

By listening to people’s stories researchers in this Project were able to focus on what and 

how the participants communicated their experience. Some people changed how they 

drive the car after seeing their instantaneous fuel economy; others drove the PHEV as any 

other car, and specifically like they had no particular control over energy use. Some 

people likened plugging in the PHEV to recharging a cell phone and made it part of their 

daily routine, but were hesitant to recharge outside of their homes due to a lack in social 

etiquette and concerns for safety. This group may feel a need for recharging locations in 

the public sphere to solve the problems of social relations as much as to maximize their 

CD miles. Many people were confused about the state of charge of the battery; this 

influences how often they recharged. Some were concerned about the cost of the PHEV 

and payback; they saw PHEVs as helping with environmental problems but wondered 

how much they were paying to do so. 

In the context of the present Project, locating the reasoning behind people’s actions and 

decisions allows for researchers, policymakers, vehicle manufacturers, and electricity and 
 83 

fuel suppliers to recognize how households arrive at actions and decision. This is useful 

because it allows those interested to shape the direction of the market and the future of 

the product, in this instance, PHEVs. Narratives are a vital part of this study as they help 

formulate a comprehensive view of each household and their reaction to PHEVs. 
 84 

3D. PROJECT RESULTS: INTERFACES AND INSTRUMENTATION

In this section we describe the information interfaces that were available to drivers of the 

PHEV-conversions used in this Project and the observed impacts of and problems with 

those interfaces. The first part of this section describes each interface (Figures 28 through 

34). The second part of this section describes the reactions of PHEV drivers to the 

information in the form of themes that arose from the household interviews. Finally, the 

possible impacts of the interfaces on driving behavior are discussed. 

The people we discuss in this section were in the first twenty-one households in the 

Project. 29 These households all had the PHEV-conversions for four weeks; the vehicles 

had the conversions on-line for the entire time. However, we did not provide these 

households with access to their vehicle data via a website until our mid-term visit to the 

household two weeks subsequent to the delivery of the car. Thus, these households first 

had access only to the instrumentation in the car, then were provided with an explanation 

of, and access to, the website for the last two weeks they had the PHEV. 

Interface Details 

There are two main sources of vehicle information available to study participants. First, 

the primary vehicle interface is the stock display console screen in the 2007 and 2008 

model Priuses used in the Project. The Energy Monitor screen shown in Figure 28 is a 

schematic representation of energy flows in the vehicle as well as the instantaneous fuel 

economy (labeled “Current” at the bottom of the screen). The schematic shows the type 

of energy (Gas, Electric, Electric Regenerative) by both arrow color and direction. 

The PHEV conversion process amends the Energy Monitor screen to distinguish between 

the stock Prius battery and the supplemental conversion battery. The Energy Monitor 

screen was probably the most viewed by drivers in the study, at least in part because it is 

programmed to appear automatically at the start of a trip. Although the interface allows 

 

29 Based on the results reported here, households after these initial twenty-one have been provided with 

access to their data on the website from the beginning of their PHEV trial. 
 85 

users to turn off the screens, the PHEV-conversions tend to switch the screen on when the 

car is started even if a driver had previously turned it off. The in-vehicle interface was 

fairly successful in generating interest from participants because of its place as the default 

screen option in the vehicles, as well as its relative simplicity. 

Figure 28: Energy Monitor 

The Consumption screen shown in Figure 29 shows instantaneous fuel economy as a 

column chart on the far right. To the left appear columns indicating five-minute averages 

of fuel economy, with the most recent five-minute period on the right. Every five minutes 

the chart indexes one place to the left and the new five-minute-average column appears at 

the right-hand side of the graphic. In addition, small green car icons, or “turtles” as some 

of the households called them, appear within the columns of this chart. Each represents 

fifty watt-hours of regenerated electricity from the generator, as noted in small text below 

the screen title at top-left. From right to left at the bottom right of the screen there is a 
 86 

button to reset average fuel economy, the distance driven since the last reset, and the 

average fuel economy since the last reset. 

Figure 29: Consumption Monitor 

Second, participants had access to the data they generated through driving, recharging, 

and refueling the vehicle via a website designed by the on-board data system provider. 

The website displays vehicle summary data as well as the location and status of the 

vehicle. The web tool was not originally intended for use by individual drivers, but rather 

by fleet managers, and although changes were made to make the site accessible by the 

participants in this study, the information is in general highly detailed, located across 

multiple pages and behind tabs, and presented (with one exception) in numeric and 

tabular form rather than iconic and graphical forms that might illustrate relationships. 

Example screenshots of the web-based interface are shown in Figures 30 through 34. 

Although the website provides detailed summary information—for example, driving data 

are summarized by trip, day, week, fortnight, and month—few participants reported 

being influenced by the website due to the effort required to access and then interpret the 
 87 

information. The website requires participants to view their vehicle’s information on a 

web-connected device—typically, the household’s home computer—rather than having it 

presented to them automatically and in the vehicle. Furthermore, once a participant views 

the website, they must then exert additional effort to make use of the resource due to the 

variety and complexity of the information presented. 

Figure 30 displays the entry page of the website. The graphic at the top is enlarged in 

Figure 31. This graphic remains across all pages and tabs. The top half of the graphic 

shows the distance driven each day (bar height) as well as the proportion of electric and 

gas energy used to accomplish that driving (green represents electric energy). The bottom 

half of the graph shows the supplemental battery’s SOC (green line). 

Figure 30: Entry Page 
 88 

Figure 31: Entry Page Energy Use Chart 

The Performance Comparison table at bottom-left of the entry page (shown in Figure 32) 

summarizes the driver-vehicle’s (gasoline-only) fuel economy, carbon-dioxide equivalent 

per mile (CO2e/mi) emissions, and estimated cost per mile—all over three time spans and 

in comparison with the fleet of PHEV-conversions in the Project (Fleet), and estimates 

for the national US light-duty vehicle fleet (National Average). In general this table 

didn’t attract the interest of participants, though a few households reported that the cost 

per mile information was useful to them. 

Figure 32: Entry Page Performance Comparison 
 89 

The Detail Table shown in Figure 33 shows various indicators for the car over three time 

periods. Very few participants reported using this table. 

Figure 33: Entry Page Detail Table 

Clicking on the Trips tab on the Entry Page causes the table shown in Figure 34 to appear 

underneath the graphic shown in Figure 31. This table was by far the most interesting part 

of the website to the largest number of participating drivers. Summary information about 

each trip, including duration, distance, battery SOC at the beginning and end of the trip, 

(gasoline-only) fuel economy, and (gasoline plus electricity) estimated cost are presented. 

The indicators are then reported for the whole day in aggregate. Many users were 

particularly interested in trip fuel economy. 

Figure 34: Trips Tab 
 90 

An additional bit of feedback technology was not installed or visible in all vehicles: a 

small LED that lit when the supplemental conversion battery was active. Some 

participants found that it was a useful piece of information. 

Interface Themes from Household Interviews 

Participant perceptions and use of the interfaces were included in the household 

interviews to varying degrees depending on participant’s interest. These responses were 

then integrated into the household narrative using the methods described in the Narrative 

Analysis section. Relevant narrative excerpts from all of the 21 households were then 

collected into a single document and read specifically for the purpose of interface theme 

development. Common ideas, perceptions, or statements of interest relevant to the 

interfaces were identified and followed through the set of narratives. In describing the 

themes that were found, the greatest weight was placed on themes that occurred in many 

households, although ideas found in as few as two households are discussed here. In 

addition, an attempt was made to qualify the extent to which a given theme is common or 

uncommon across the twenty-one households in the group; interesting statements from a 

single household were identified as being singular. 

Limited use of Web Resources 

Accessing the website was a major barrier to some households due to inconsistent 

Internet access, the complexity of the information presented on the website, or simply 

because it required additional time and effort on the part of the driver. In addition, 

household-specific dynamics caused problems in some households. For example, Nancy 

cares for her elementary-school aged grandson. When asked about the website, she 

replied that her grandson was too much of a distraction to let her concentrate on the 

website for long. Rick Lake also commented his children made it difficult to peruse the 

website at home. Still, children were not the only cause of inattention to website; several 

households without children also found that logging on to the website was one more task 

they were unable or unwilling to fit into their daily lives. 
 91 

Abstract Information 

Many participants had trouble placing the information from the interfaces into a useful 

context. In particular, instantaneous and even time-averaged fuel economy available in 

the vehicle seemed to raise, rather than answer, questions: “[the interface] doesn’t really 

tell me if I am doing better than yesterday,” said Frank. Similarly, Sarah told us, “I did 

notice that the car was using more battery, but there was nowhere I could see how the car 

performed differently when the battery was charged or depleted.” Many participants did 

not perceive that they had control over fuel economy, as reflected in Samantha Lake’s 

comment that, “the car is going to do what it is going to do.”30 

Although the vehicle and website interfaces gave users detailed information about this 

vehicle, it was a challenge for participants to integrate this information into an overall 

sense of savings, in part because the concept of savings requires a comparison to another 

vehicle. Possibly for this reason, many participants estimated their savings by using the 

difference in the total cost of a tank of gasoline, gallons pumped, or refueling frequency 

between the PHEV and a familiar household vehicle.

Confusion 

The in-vehicle screens and website both caused considerable confusion among many 

study participants. As Nancy told us referring to the in-vehicle interface, “I watch. I try to 

watch...I thought that I was getting it, but I think I am just confused.” A few of the main 

sources of confusion are outlined below. 

Conversion Battery Information 

There was no clear indicator of the energy battery charge state and most users 

wanted a clearer indicator. Again, Nancy had difficulty, saying, “I am not sure 

when I’m using the gas or the battery.” 

 

30 It is not clear in this context whether information and feedback would help these people develop a sense 

of control, or that a sense they lack control is a more pervasive stance that these people have toward 

automobiles or even life more generally. This will be explored in subsequent research. 
 92 

IFE (Instantaneous Fuel Economy) Fluctuation 

Drivers were generally unable to draw conclusions from the IFE reading on the 

Fuel Consumption screen. Some were put off by the rapid fluctuations, and many 

reported they were unable to make a good measure of overall fuel economy from 

that metric. When asked to estimate his fuel economy, Rick Lake said he 

observed the IFE indicator to be “99.9 half the time, and 50 otherwise,” making a 

precise estimate impossible for him. 

Reinforcement of Counter-productive Braking Behavior 

The IFE and “turtles” displaying regenerative energy both perversely indicate that 

decelerations and braking result in the highest fuel economy, whereas any 

unnecessary deceleration is always a loss of energy from a system perspective—

even if some of that energy is recaptured through the electric drive system. Many 

drivers seemed to be attracted to the 99.9 IFE readouts and the accumulation of 

turtles, without correctly connecting those to the effect on fuel economy. As 

Penny said, “[I] tried to get the little green cars going.” 

Novelty 

For some users, the screen information is reported to be interesting only for a short 

period, and these users don’t think they would stay engaged in using the information to 

drive more efficiently over the long term. Similarly, some participants enjoy looking at 

the interfaces, but don’t consciously connect that information to possible behavior 

change. Billy Woods told us, “It’s like changing stations on the radio,” and, “I’m always 

looking at that screen...out of curiosity...I’m going this speed, is it using gas? Are the 

tires generating [electricity to] the battery...and more so during the beginning of the 

study because I was trying to figure out how everything was going.” Similarly, the 

Millers also reported that the V2Green website was interesting, but only the first few 

times they viewed it. 
 93 

Learning from Interfaces 

Slowing Down 

Many drivers report slowing down on the freeway due to the low IFE readings 

during high-speed driving. Some of these readings appear to have been 

misinterpreted due to the mixed effects of vehicle cruising speed, accelerations, 

and decelerations. However, the overall behavior changes reported by drivers 

using the IFE measure were sensible, such as driving more slowly than their 

normal freeway cruising speeds. Casper told us that when observing the in-vehicle 

interface he would “slow down a little more,” on the highway, reducing his 

cruising speed from 80 to 70MPG in order to achieve higher fuel economy. 

Devon seemed even more motivated by the in-vehicle display, stating, “Coming 

home I stayed in the slow lane, 65 or not even 65, to get the [consumption screen] 

bars all the way [up], watch[ing] to see the consumption.” 

Learning to use Lower Accelerations 

Some drivers reported attempting to keep the IFE high by accelerating slowly, 

and generally assumed the instantaneous impact correlates with overall reductions 

in fuel use, “if you are nicer to the [accelerator] it gets a lot better mileage,” said 

Cindy Mackson. Sarah told us, “It gets me to slow down, rather than giving you 

that gunshot start...It gets you in that gear to pay attention to how fast you are 

starting up, versus just going in a normal car.” 

Learning to Recharge 

The website was instrumental in teaching a number of participants to recharge 

their PHEV-conversions more often. Some had either incorrectly plugged-in the 

vehicle or erroneously assumed that the battery was still charged. Said Billy 

Woods, “that’s how I knew that the socket was bad at my girlfriend’s house...I 

went into the website and it said I was disconnected.” Devon simply didn’t realize 

how much of a difference the battery made until he was given access to the 

V2Green website. After receiving the login information Devon reported looking 
 94 

at the website almost every night. Both the battery SOC as well as trip summary 

mpg information seemed to motivate participants to recharge more frequently. 

Gender Differences 

Many households displayed a gender difference in regards to responsibility for, and 

interest in, fuel economy, watching the in-vehicle interface, and going online to check 

performance summaries. It was common across households with a female and male head 

of household for men to play these roles; more women reported they drive to simply get 

places with less concern for the details. It was clear that these were pre-existing roles in 

many of these households and the in-vehicle and website information were novel sources 

whose use fit patterns of existing behavior. One notable exception is the Mackson family, 

wherein Michael and his daughter Cindy vied in friendly competition to get the highest 

fuel economy (this household is described in more detail below). 

Goal Setting 

Some drivers used the interfaces to set, or check the achievement of, goals. Although a 

minority of participants reported setting fuel economy goals, those who did tended to be 

in households with the highest overall average fuel economy, indicating that goal setting 

may be an important part of achieving and maintaining high fuel economy. Fred Sampson 

used the energy screen to help him drive “to midtown without using the engine at all.” 

Rick Lake used the V2Green website to verify he had achieved his goal of a round-trip to 

work with a trip average of 100mpg. Rainn Thompson used the battery charge indicator 

to try to make a commute roundtrip without exhausting the supplemental battery. 

Impact of Additional Summary information on Fuel Economy 

We hypothesized that the additional information provided by the website would lead to 

an increase in overall fuel economy. However, due to the wide variation in factors 

between the periods when the households had access to different types and levels of 

information, such as city or highway driving proportion, weather, and road conditions, 

long trips taken during either the without- or with-access to the website phases, a wide 

variance was seen between these two phases of the study. The performances of 
 95 

households in these two phases are summarized in Figure 35, which shows the change in 

average (gasoline-only) fuel economy from the without- to the with-website phase for 

each of 20 households.31 Counter to our hypothesis, people who reported using the 

website were more likely to decrease, not increase, their overall fuel economy than were 

non-users of the website. 

Figure 35 Change in fuel economy from without-access to with-access to 

the V2Green website (change is represented as the percentage change 

from the harmonic means of the first and second phases). 

One reason for these changes appeared to be a regression to the mean, as many of the 

households in the website users group had higher fuel economy from the beginning of the 

study, yet lost motivation to continue modifying their driving behavior as intensively—

despite the additional information on the website. Household 5201, who had by far the 

greatest mpg increase, kept the vehicle in CD mode during the entire second half of their 

placement. Their increase was due to 1) changes in driving behavior—the couple 

 

31 Data from one household was excluded due to anomalies generated by the in-vehicle data system. 
 96 

reported that they were interested mainly in the information from the stock Energy 

Monitor and Consumption screens and had used the information to modify their driving 

behavior to achieve higher fuel economy, and 2) an unrelated decrease in trip lengths 

between the without- and the with-website phases. 

Although it would be inappropriate to generalize from a sample with such varied 

outcomes, a few participants related their own experiences clearly enough to discuss at 

greater length below. These two households show the complex relationship between fuel 

economy information, initial knowledge, motivation, and short-term behavior change. 

Michael and Cindy Mackson (5203) 

Michael and Cindy live in an older part of central Sacramento. They both drive Volvo 

station wagons they purchased used. They engage in numerous pro-environmental 

behaviors such as vegetarianism and recycling. From the beginning of the study, they 

were both very interested in the PHEV as a way to reduce their environmental impact. 

When asked about the vehicle interfaces, Michael reported constantly scanning the fuel 

economy information on the Energy Monitor screen. Cindy also reported looking at the 

Energy Monitor and Consumption screens, using them to help keep her accelerations low. 

Both were “feathering” the gas pedal (using a light touch to accelerate and ease off) to 

see if they could get better mileage, a technique Cindy uses with her other car as well. 

They both reported trying to keep the Energy Monitor screen “in the blue,” meaning allelectric operation in CD mode.32 Cindy mentioned that having the screen helps her 

moderate accelerations from stop signs and traffic signals, although she and Michael 

were concerned about irritating other drivers by driving or accelerating slowly. Michael 

mentioned that people driving quickly from the stop sign have a “crowd mentality” that is 

easy to fall back into. He finds himself anticipating lights and leaving more room 

between his car and cars in front of him, both to give him time to look at instruments and 

to stay a little behind traffic. He estimated that half the time he drives normally, the other 

 

32 In the PHEV conversions, the supplemental conversion battery is shown as blue and the stock battery as 

green on the Energy Monitor. 
 97 

half he is actively trying to save gas, and that he could see a 10% overall difference 

between the two. (This seems like he is making a rough estimate, not a careful calculation 

or observation.) Cindy also characterized saving gas as a fun experiment or challenge. 

After giving them access to more information about their vehicle on the website, Michael 

reported looking at it “all the time,” even using it to track Cindy for fun. Michael mostly 

used the website to look at (gasoline-only) fuel economy (mpg) for the day, although he 

would also look at individual trips. They were both interested in tracking CO2 for 

environmental reasons, but Cindy felt that the information on the website was too 

abstract: she didn’t know if a given amount of CO2 per trip, day, week, or month was 

good or bad and wanted an easier way to understand their emissions, stating, “...you 

can’t attach [CO2] to anything to make it make sense.” She mentioned that seeing how 

many trees it would take to soak up her CO2 output would be motivating. Michael wanted 

to see a comparison to well-known vehicles, telling us “You know, if you want to get 

down to nuts and bolts and compare these to like a Honda Civic or a [Toyota] Corolla it 

would be interesting to see how it does against that.” 

Overall, the Macksons increased their aggregate gasoline-only fuel economy from 58 to 

59 mpg from the first half to the second half of the study.33 Although they at first appear 

to be a model household for improvement due to their high level of motivation, their 

previous use and knowledge of fuel economy techniques and high initial average fuel 

economy also means that they had less room for improvement in the second half of the 

study. The Macksons also had a very consistent commute patterns and did not take many 

out-of-town trips, making it easier to compare the first and second halves of their trial. 

Rick and Samantha Lake (6201) 

Rick described a shift in his use of the PHEV over the course of the trial: “it was a 

novelty at the beginning...I was babying it a lot...now I just drive it normal.” At first he 

 

33 The fuel economy numbers discussed by households and presented throughout this discussion are 

aggregate measures covering both CD and CS operation of the vehicle; they do not include any of the 

electricity used in CD mode. We adhere to this incomplete measure of energy use in this discussion 

because it is how these households perceived and reported their experience. 
 98 

liked to monitor his IFE as well as the Energy Monitor diagram of the energy flows in the 

drive system to see if the battery was being used. He would experiment with different 

behaviors: “I’d gas it and watch it...put my foot off the throttle and watch it ...out of 

curiosity to see how my actions affected things.” He said it was this curiosity that caused 

him to watch the instrumentation “more than [he] should.” Rick was also motivated by 

his goal of achieving 100 mpg or higher during his commute. 

In contrast to Rick’s initial focus on the fuel economy instrumentation, his spouse 

Samantha stated: “I’m the opposite: oblivious...just driving...I pay attention to the road 

mainly.” She reasons that because she is driving fast she has “got to pay attention,” and 

thinks that Rick looks at the screen too much. As Rick talked about trying to achieve an 

IFE of 99.9 mpg on the highway, Samantha added, “People are honking at you.” 

Once the household was given access to the website, Rick made regular use of it, but 

Samantha reported that she did not use it. At the midterm interview, prior to being given 

website access, Rick was highly uncertain about his overall fuel economy. He noted he 

had not yet had the chance to make a precise estimate because he hadn’t refueled the 

PHEV, and he normally calculates fuel economy when he fuels his vehicle. After getting 

website access, he would regularly scan the website at work, mentioning that the kids 

were too distracting at home. He says he looked at everything on the website, but found 

the trip and daily average fuel economy most useful—the rest was less useful, “gee-whiz” 

information. While he claims not to have used the website to change his driving habits, 

he feels he would use the website at least weekly in the long-term. Due to his continued 

monitoring of his vehicle performance on the website, Rick was more knowledgeable 

about his fuel economy by the end of their four-week PHEV placement. 

Rick and Samantha achieved a relatively high average 63 mpg over their whole four 

weeks driving the PHEV; but it dropped from 75 to 61 mpg from the without- to the 

with-website phase. Rick and Samantha identified two reasons for the sharp drop: longer 

trips out of town in the PHEV and Rick driving “more normally, more aggressively” in 

the second two weeks. Although we don’t know the relative impact of those two factors, 

Rick’s behavior vis-à-vis the additional information on the website was prevalent among 
 99 

the group with the highest fuel economy in the first half of the study—they lost 

motivation to maintain new driving practices that allowed them to achieve high fuel 

economy in the first half of their PHEV trial. 

Information Interface Conclusions 

It is impossible at this time to generalize the impact of in-vehicle and internet-based 

information interfaces on fuel economy based solely on the information gathered as part 

of this Project. Certainly it is not possible to conclude that energy interfaces have no or 

deleterious effects on energy use, despite the data in Figure 35. Each participant 

interacted with the available vehicle information in a different way. Some of the major 

reasons for the differences seemed to be their prior interest in fuel economy (interest in 

fuel economy changed and often increased over the course of the study), technological 

fluency, their role in the household in regards to vehicles or technology, as well as many 

other factors. Some participants completely ignored the information while others found 

the information to be a stimulating and engaging learning tool. From the themes 

identified in this section, we propose a few basic lessons that may help future interface 

designs facilitate driver improvement in fuel economy: 

• The closer the information is to the point of interest and action, i.e. in the car vs. 

on the home computer, the more likely it is that the information will be used. 

• Simplicity in representation and interpretation is critical to driver understanding. 

• The interface should support drivers in setting and achieving goals by providing 

relevant summary information. 

• Instantaneous Fuel Economy can provide drivers with erroneous information, 

especially during braking events. 

• Whenever possible, information should be presented in a grounded context so that 

drivers can quickly understand the relative impact of their behavior. 
 100 

Although these general lessons are by no means definitive or complete, they represent a 

simplified interpretive summary of the many participants’ responses to the interfaces 

included in this study and as the basis for the design of ongoing research to elaborate and 

specify these lessons. 
 101 

3E. PROJECT RESULTS: SOCIAL INFLUENCE

Background 

The question of how and why consumers buy new products is central to the successful 

deployment of alternative fuel and electric-drive vehicles. In conceptualizing the role of 

interpersonal interactions in the adoption of new products, one approach has dominated: 

diffusion of innovations (DOI), conceptualized as the process of information diffusing 

from innovators and early adopters to the remaining majority via interpersonal 

communication.34 DOI offers some advantages, e.g., a common language across 

disciplines, but it has important limitations that are exacerbated when DOI is uncritically 

applied to the adoption of complex technologies and ideas. Electric-drive vehicles 

exemplify such complexity; they are innovative in a technological and functional sense, 

but also present a radical shift in symbolic, and in particular, pro-societal benefits.35 In 

the DOI approach, a PHEV or another electric-drive vehicle is typically labeled a 

technological “innovation” (e.g. Rogers, 2003). From a manufacturers’ perspective what 

is new about electric-drive vehicles (EVs, HEVs, and PHEVs) is that electricity is used to 

power the vehicle. Consumer perceptions are more complex and amorphous than this. 

Not only must we consider how an innovation is functionally different from its 

predecessor, but we must also ask how the new functional and symbolic attributes of this 

technology are important to consumers. Table 6 presents a conceptualization of PHEV 

attributes according to two dimensions: functional/symbolic and private/societal. 

PHEVs and other electric-drive vehicles are innovations because of what they can 

physically do: new battery and drivetrain technology allows users to offset gasoline use 

with electric-drive capabilities and to plug-in to the electrical grid, often at home. From a 

functional perspective, consumers may interpret the desirability of electric-drive 

 

34 Due to the ubiquity of DOI, before we introduce alternative perspectives we will rely on DOI 

terminology, including: “innovation” as the object, idea or practice of interest; “adoption” as the purchase 

or taking on of the innovation; and “diffusion” as the spread of information about the innovation through a 

social system. 

35 Both the terms “pro-societal” and “pro-social” refer to benefits that can only be collectively realized by 

multiple parties; we use the former term to avoid confusion with the social processes discussed here, i.e. 

interpersonal interaction. 
 102 

technology according to its ability to save them money on transportation, to improve 

drivetrain reliability, or to simply improve the experience of driving. 

Table 6: Conceptualization of PHEV attributes (hypothetical examples) 

 Functional Symbolic 

Private • Save money 

• Reliable 

• Fun to drive (experiential) 

• Expression of self-identity 

• Convey personal status to others 

• Attain group membership 

Societal • Reduce air pollution 

• Reduce global warming 

• Reduce oil use 

• Inspire other consumers 

• Send message to automakers, 

government, oil companies 

However, a singular focus on function neglects important aspects of human behavior. 

Hirschman (1981) proposes a second category of innovation: symbolism. In addition to 

tangible and functional services, Hirschman (1981, p537) defines symbolic innovations 

as being able to communicate a “different social meaning” than a previous technology, 

and hypothesizes that such innovations may “possess fundamentally different properties 

and diffuse according to fundamentally different principles” relative to purely 

technological innovations. Heffner et al. (2007) investigated the role of symbolism 

among HEV owners, finding five general symbolized meanings that motivated HEV 

purchase: preserve the environment, oppose war, manage personal finances, reduce 

support to oil producers, and embrace new technology. 

In addition, electric drive vehicles embody another class of attribute that differentiates 

them from conventional vehicles: the potential to benefit society. Green (1992, p133) 

provides a framework to classify goods on a private/public scale, where private good are 

characterized by “exclusive and personal consumption and individual payment; not 

associated with the public welfare,” whereas societal or public goods are characterized by 

“nonexclusive consumption and collective payment” such as “clean air” and “saving 

endangered species.” Canzler (1999, p25) asserts that to date, motor vehicles have been 

primarily perceived as private goods, dating back to the original “race-travel-limousine” 
 103 

of early car buyers motivated by goals of luxury and prestigious racing. However, 

electric-drive vehicles may present a divergence from private goods due to their potential 

to produce pro-societal benefits, such as contributing to reductions in air pollution, 

greenhouse gas emissions, and oil dependence—or by encouraging others to think of and 

act on such issues. Thus, electric-drive vehicles can be associated with public welfare, 

leading Brown (2001) to classify the EV as a mixed good, that is, having aspects of both 

a private and a public good. Further, such interpretations and reinterpretations may 

develop over time; for instance, Gjoen and Hard (2002, p264) describe how one 

consumer’s experience with an EV led her to “become an agent contributing to the 

deconstruction of what a car is meant to be and to the construction of a new sense of 

mobility.” In summary, the so-called “diffusion” of electric-drive vehicles will entail an 

ongoing social discourse about the functional, symbolic, and pro-societal benefits. 

To investigate the role of interpersonal influence in the formation of functional, symbolic 

and pro-societal interpretations of electric-drive vehicles, three general research questions 

are posed: 

1. Do interpersonal interactions play a significant role in the assessment and 

adoption of electric drive vehicles? 

2. If so, how can we characterize the interpersonal interactions that influence 

consumer perceptions of functional, symbolic, and pro-societal attributes? 

3. Under what social conditions might households adopt electric drive vehicles and 

the pro-societal car? (And how might policy create those social conditions?) 

Methods: Observing Interpersonal Influence 

To explore the potential roles of interpersonal interactions in the adoption of pro-societal 

cars, an extended methodology is being applied to the social networks of a subsample of 

10 to 15 households participating in the Project; analysis of the networks of four 

households have been completed as of the writing of this report. Researchers work with 

each of these households to map, measure, and stimulate episodes of social interaction 

within the households’ social networks, as illustrated in Figure 36. 
 104 

Social network analysis has been frequently applied to diffusion studies; instead of 

emphasizing the individual as the unit of analysis it explores the role of linkages between 

individuals (Rogers 2003). Social network analysis investigates how the structure of these 

linkages (or ties or relationships) influences the diffusion process (Granovetter, 1973; 

Degenne and Forse, 1994). While it may be ideal to study social processes and structure 

at the “total” network level—by accounting for every link among all individuals in a 

social system—in most situations it is only feasible to collect data from different personal 

networks (Degenne and Forse, 1994; Carrasco, Hogan et al., 2008). A personal, or 

egocentric, network is represented by: i) the primary individual (the grey and black circle 

in Figure 36), ii) the other individuals they are socially connected to (the white circles), 

and iii) characterizations of the relationships, or ties, between all individuals (the 

connecting arrows) (Carrasco, Hogan et al., 2008). 

Figure 36: Stimulating Social Networks with PHEVs 

Stage 1: Primary Informant Constructs Personal Network

Screener

Interview to Map

Personal Network

and Elicit Contacts

Stage 2: Collect Baseline Information From Network

Online Survey

Screener

Elicit Personal 

Network Info

Online Survey

Stage 3: Stimulate Network with PHEV Trial

Stage 4: Network Questionnaire and Selected Interviews

Closing Interviews

(Selected 

Respondents)

Online Design

Game

Checkup Interview

Closing Interview

Design Game

PHEV Placement

Eliciting personal network data can be very challenging, including efforts to scope 

network size, overcome limitations in respondent recall, and mitigate respondent burden 

(Marsden, 1990; Carrasco, Hogan et al., 2008). In this project, we use a technique 
 105 

outlined by Hogan et al. (2007), which assists participants in the creation of a 

sociogram—a graphical depiction of their personal network. Participants are asked to 

generate a list of “very close” and “somewhat close” contacts—terms kept intentionally 

vague—on a series of post-it notes, then arrange the names on a poster with four 

concentric circles representing social closeness. 

This project follows a “multi-method” approach (McCracken, 1988, p28) including 

structured interviews and internet-based questionnaires, as well as social episode diaries. 

In social network studies, asking respondents to keep diaries of social episodes can be 

invaluable to enhance recall of interactions with other contacts during a particular period 

(Degenne and Forse, 1994, p19). The four stages illustrated in Figure 36 are implemented 

as follows. 

Stage 1: Contact primary household and elicit personal network. 

Households were selected from the same sampling frame used for all Project participants. 

Along with being screened for eligibility and completing the online questionnaire, the 

Project participants in this personal network study (Primary Households) engage in an 

extended household interview, including: 

1. Household vehicle purchase history: draw out narratives of the vehicles 

currently and previously owned by the household, including the perceived 

benefits and drawbacks of each. 

2. Future vehicle purchase intention: elicit potential future plans to purchase 

a new vehicle, including the primary objectives of purchase and any 

specific models being considered. 

3. Personal network mapping: identify a network of people who are “very 

close” and “somewhat close” to the household’s, i.e., the “ego” in an 

egocentric network. Primary households are then instructed to personally 

invite members of their network to the study. 

4. Social-episode diary: provide a diary for the primary household to make 

brief notes regarding any social episodes in which they discuss PHEVs, 
 106 

electric drive, or vehicle purchases in general over the multi-week period 

of the PHEV trial in Stage 3.

Stage 2: Collect baseline information from the personal network. 

The primary household recruits members of their primary personal network to the study 

(secondary participants). Those network members willing to participate complete the 

same screener and internet-based questionnaire as the primary household. Secondary 

participants confirm the existence and nature of the relationships (connecting lines in the 

sociogram) as elicited from the primary household 

Stage 3: Stimulate personal network with PHEV trial. 

After the personal network has been mapped, the primary household begins their PHEV 

trial, completing several tasks, including: 

1. The social episode diary.

2. The online PHEV design questionnaire. 

3. Midterm interviews every two weeks. 

4. A closing interview, consisting of questions regarding the following: 

a. The household’s overall experience with the PHEV (narrative). 

b. Recharging, driving, and fueling behavior. 

c. Functional, symbolic, and pro-societal interpretations of the 

vehicle, and the dynamics of these interpretations over the course 

of the trial. 

d. Contacts with members of the personal network (and others) 

including the content and frequency of such discussions, as well as 

the perceived influence over the primary household’s assessment 

of PHEV technology. 

e. Assessment of interests in future vehicle purchases (assisted by 

previously elicited responses in the PHEV design questionnaire). 
 107 

Stage 4: Network questionnaire and selected interviews. 

At the close of the primary household’s PHEV trial, secondary participants are again 

contacted to share their observations of the primary household’s PHEV trial. All 

secondary participants complete the online PHEV design questionnaire, which also elicits 

information about any social episodes that occurred with the primary household during 

the trial. A subset of secondary participants take part in a telephone interview, including 

details of any experience with the PHEV, interpretations of the vehicle over the trial, 

specific social interactions with the primary household or others during the trial, and 

interests in future vehicle purchases. 

Some Preliminary Results 

To illustrate the methodology used to elicit network data, Figure 37 portrays the 

sociogram of Billy Woods, as well as the patterns of interaction observed within his 

network during his PHEV trial. Billy identified 44 people as “very close” or “somewhat 

close” as categorized on the y-axis—circles closer to Billy, i.e., closer to the bottom of 

the figure, represent a closer social relationship to Billy. Billy mentioned or discussed the 

PHEV with 11 of these contacts during his trial, identified by letters A through K. Billy 

also mentioned or discussed the PHEV with eight casual acquaintances (letters I through 

Q) who he did not place close to him in his network map, and one stranger that he met 

during his PHEV trial (letter R). Figure 37 also groups Billy’s social contacts according 

to his descriptions of how close they are to one another (with line thickness proportional 

to the strength of ties), with subgroups labeled where possible, such as “family,” 

“coworkers” and “golf buddies and friends.” People recruited as secondary participants 

are identified with a thicker circle (F, J, K and R). Finally, the darker shading in circles 

indicates that Billy considered interactions with that individual to have had relatively 

higher influence on his assessment of PHEV technology. Thus, his interactions with the 

stranger “R,” casual acquaintance “L,” and friends “D” and “E” were more influential to 

Billy than his interactions with family members “A” or “B,” his girlfriend “F,” or others. 

Figure 37 can be viewed as one map of Billy’s social network as well as an overview of 

how his PHEV trial stimulated this network. 
 108 

Table 7 provides summary details of the four networks investigated so far, including the 

primary households—Billy Woods, the Noels, the McAdams and the Rhodes—and the 

secondary participants they recruited. Table 7 also shows the primary households’ 

perspective of the social proximity of the secondary participants and the influence of 

interactions with them, as well as the perspective of the secondary respondents. These 

perspectives are not always symmetrical; for example, although “Chris” (K) considers 

Billy to be a very close friend who had a strong impact on his perception of PHEVs, Billy 

did not recall having spoken with Chris during his trial. Asymmetry occurs in the other 

direction also; Billy rated his interaction with a stranger who was an EV driver, Harry 

(R), to be highly influential, while Harry in turn did not consider the interaction to be 

influential for himself. 

Figure 37: Billy Woods’ Sociogram 

1st Circle

2nd Circle

3rd Circle

4th Circle

Casual

Acquaint.

Stranger

Family

Out-of-State

Friends

Former

In-Laws

Longtime

Friends

Golf Buddies

and Friends

Coworkers

Girlfriend and

Her Daughter

Social Proximity to Billy

Didn’t discuss PHEV w/ Billy

Lower influence interaction

Mod influence interaction

Higher influence interaction

Interviewed secondary

Somewhat close tie

Very close tie

X

X

X

X

Billy Woods

While Figure 37 and Table 7 provide interesting overviews of some general patterns of 

interpersonal interaction, they exclude important finer details. The data collected in this 

Project is quite extensive, with over 100 person-to-person interactions described by the 

four households—most are brief, but some are very important to either the primary or 

secondary participants’ evaluation of the PHEV-conversion and PHEVs more generally. 
 109 

One starting point for differentiation among these interactions is the networks 

themselves, which include individuals engaged in different lifestyle practices, resulting in 

different levels of experience and interest with electric-drive vehicles, “green” 

technology, and pro-societal behavior. Giddens (1991) describes a lifestyle as a package 

of practices associated with an individual’s particular trajectory in which behavior is 

guided by efforts to establish a sense of order, direction, and development for the 

individual’s self-concept. These practices include fashion, eating, and any other “means 

of symbolic display...giving form to narratives of self-identity” (Giddens 1991 p. 62). As 

discussed earlier, the symbolic aspects of automobiles place the purchase and use of 

motor vehicles within this process of creating and enacting a lifestyle. This differentiation 

of lifestyles is illustrated with a brief summary of each of the networks in Table 7. 

The Noels as electric-drive novices 

Rupert and Amy Noel live with their three young children in Sacramento. They are 

highly family-oriented—demonstrated not only by their devotion to their children, but 

also by frequent interactions with their large extended family. The Noels had no 

experience with electric-drive vehicles prior to their PHEV trial and they have no 

electric-drive experts within their social network. Throughout their trial, Rupert’s 

interactions mainly consisted of “showing off” the vehicle to friends and coworkers, but 

he reported these interactions had little influence on him. In contrast, Amy more actively 

attempted to advance her functional understanding and assessment of the PHEV by 

eliciting the perceptions of friends, family, coworkers, and even her dentist. Above all 

else, the Noels’ agreed that the most influential interactions they had were in sharing the 

PHEV experience with their own children, such as adding the words “hybrid” and “plugin” to their 4-year-old’s vocabulary. In all their conversations with members of their 

personal network, the Noels’ talked only about basic private-functional aspects of the 

PHEVs, e.g. recharging and fuel economy. These concepts were not well understood by 

the Noels or clearly communicated to others—all interviewed secondary participants 

(John, Ray and Anita) were unsure of the differences between an HEV and PHEV, and 

none had a strong sense of what benefits the PHEV offered, beyond generally improved 

fuel economy. 
Table 7: Summary of primary households and secondary participants in the personal network study to date 

 110 

For primary: For secondary: Primary household 

(network size and interactions) 

Secondary 

participant 

Age Household 

income 

Lifestyle 

and values 

Relationship 

to primary Social 

proximity1

Infl. Social 

proximity 

Infl. 

Billy Woods 40s $100-124k Recreation  Total close: 44 Pat (F)2 40s $70-80k Family Girlfriend 2nd circle Lo Very close Hi  Close contacted: 11 June (J) 40s $80-90k Recreation Friend/coworker 4th circle Hi Very close Hi  Total contacted: 18 Chris (K) 40s $80-90k Recreation Friend 4th circle n/a Very close Hi  Harry (R) 40s $125-149k Enviro./tech. Coworker Stranger Hi Stranger Lo Rupert and Amy Noel 40s $80-89k Family  Total close: 101 John 60s $125-149k Family/tech. Coworker 4th circle Mod Casual Mod  Close contacted: 29 Ray 20s $70-79k Family Friend 3rd circle Hi Very close Mod  Total contacted: 31 Anita 30s $125-149k Family Friend 1st circle Mod Very close Hi Craig and Siobhan McAdam 40s >$150k Enviro./tech  Total close: 50 Hannah 30s $20-29k Enviro. Friend 1st circle Mod Very close Hi  Close contacted: 14 Steve 40s >$150k Enviro./tech Friend 1st circle Mod Very close Mod  Total contacted: 31 Donna 20s $20-29k Unknown Coworker Casual Lo Some. close Mod Larry and Cheryl Rhodes 30-

40s 

>$150k Family/enviro. 

 Total close: 49 Nicole 50s $100-124k Family/enviro. Neighbor 3rd circle Lo Some. close Lo  Close contacted: 23 Betty 30s $100-124k Family/enviro. Friend/teacher 3rd circle Hi Some. close Lo  Total contacted: 26 

1. Smaller numbered circles represent closer social ties. 2. Letters correspond to those in Figure 37. 
 111 

Billy Woods as an electric drive novice with an EV enthusiast in his network 

Billy Woods lives alone in a detached home. He engages in many social and recreational 

activities—frequent golfing, skiing, and visiting bars and clubs. As a self-described 

“social guy,” he discussed the PHEV extensively within his large social network, 

including his technology-oriented coworkers at a computer company. He explored the 

PHEV’s “bells and whistles” with June (J), a close work friend and mentioned the car to 

other coworkers, golf buddies, and family. Many of his conversations consisted of “small 

talk” and “showing off” the PHEV’s private-functional attributes, but he considered such 

interactions to be of low influence on him. At one point he brought up the idea of prosocietal attributes among coworkers by asking them which would provide the greater 

motivation to purchase a hybrid: the ability to save money or the environment. 

Ultimately, he agreed with his coworkers that saving money was more motivational. 

However, Billy demonstrated an openness to alternate interpretations. Interestingly, some 

of Billy’s friends thought he was driving the PHEV in an effort to be green. Billy’s most 

influential interaction was a with an EV driver at work, Harry (R), who was concerned 

the PHEV might overload the circuit they were sharing to recharge their vehicles at the 

workplace parking lot. This interaction seemed to be Billy’s only contact with an electricdrive expert—a man who built his own EV and charged it at home via a solar array—but 

the conversation didn’t progress beyond a brief functional explanation by Billy of the 

PHEV demonstration. From the perspectives of others in Billy’s network, including Pat 

(F), June (J), and Chris (K), Billy’s trial was more of a functional demonstration that an 

electric-drive vehicle could be easy to recharge and provide performance comparable to a 

conventional vehicle. 

The McAdams as pro-societal technology enthusiasts 

Craig and Siobhan McAdam have strong environmental and pro-societal values which 

are demonstrated throughout their home, including solar panels, a high efficiency electric 

heater and air conditioner, efficient light bulbs, and a Toyota Prius in the driveway. Craig 

sees the PHEV as an extension to his Prius, i.e., a way to further reduce their 

environmental impacts and dependence on foreign oil, as well as sending a message to 
 112 

automakers to support the technology. The McAdams’ social network includes people 

with similar pro-societal values and interests in advanced technology—Craig has already 

influenced at least three of them in their purchases of HEVs. Surprisingly, the PHEV trial 

did not stimulate many “real conversations” in the McAdams’ network; Craig and 

Siobhan explain that because environmental issues and actions are already such a big part 

of their lives, the trial of a PHEV-conversion did not have an enormous impact. Two 

secondary respondents in the McAdams social network described how they already have 

ongoing dialogues with Craig about different environmental technologies and were 

already aware of PHEV conversion kits—the McAdams’ PHEV trial was just another 

experience in lifestyles they regarded to be pro-societal. Craig also mentioned his PHEV 

trial to more socially distant coworkers, but he found them to be generally disinterested—

a fact that the McAdams’ found to be disappointing. 

The Rhodes as pro-societal technology enthusiasts with family values 

Larry and Cheryl Rhodes blend environmental sensibilities with family values. Larry 

considers that he is a “tree hugger” and tells everyone how much he loves the fuel 

economy of his Honda Civic hybrid. He and Cheryl dream of living in an off-grid home 

powered by solar and wind energy. But they see such environmental action not just as a 

way to reduce their environmental footprint, but also as a way to shape and support prosocietal actions in the next generation, starting with their preschool aged son, Tristan, and 

his schoolmates. The Rhodes’ liked that Tristan was excited about their PHEV trial—he 

would enthusiastically demonstrate the car’s features to friends and teachers. Around the 

same time, Larry taught a class at the preschool on batteries, bringing even more attention 

to the electric-drive vehicles. With the excitement of these children, Cheryl felt she might 

be witness to “a societal shift in perspective...that they’re saving things the earth needs.” 

Preliminary Discussion and Conclusions 

The first question in this research asks whether interpersonal influence plays a significant 

role in the assessment and adoption of electric-drive vehicles. Table 7 suggests that the 

observed social interactions are influential for primary households and secondary 

participants. The second research question delves deeper to explore and characterize 
 113 

specific processes of social interaction and influence. We describe these interactions from 

five perspectives: contagion, conformity, dissemination, translation, and reflexivity. 

Table 8 illustrates these perspectives as demonstrated by the primary households. 

First, contagion describes social interactions as the point-to-point communication of 

information. Contagion includes diffusion of innovations (DOI). In DOI, adoption is 

driven by communication, including word-of-mouth and mass media, but communication 

that is primarily in one direction, flowing from earlier adopters, e.g., “innovators,” to 

later adopters, e.g., “early adopters.” This approach superficially describes some patterns 

of interaction observed in this study, such as the “showing off” of the PHEV and 

engaging in “small talk” about its basic features. For example, Billy Woods frequently 

informed people he was driving a PHEV and briefly explained that it was different from 

regular HEV. Such information could be described as diffusing through his social 

network, where secondary participants became aware of Billy’s trial and were able to 

grasp what was new about the PHEV. However, the notion of contagion neglects many of 

the subtle but important nuances of interpersonal influence, such as why particular types 

information are selected to share, why particular types of information are remembered by 

the listener, and how such information is interpreted in various contexts. 

Further, the notion that information diffuses in one direction, from innovators toward the 

majority, is limiting. While it may be tempting to label the McAdams or Rhodes as 

electric-drive “innovators,” even they learn from, and exchange information with, others 

(and others who are not “innovators”) on an ongoing basis. Similarly, Billy Woods, the 

Noels, and their network members did not draw their perceptions from one particular 

“innovator” or set of experiences. Rather, they formed a general understanding of the 

PHEV through an ongoing discourse of social interactions that they integrated with their 

existing background knowledge. In addition, although notions of contagion and diffusion 

may apply to certain “simpler” interactions, such interactions are typically identified by 

participants as less influential. 

Second, conformity focuses on individual’s perception of social norms and the actions of 

others. The approach typically includes the idea of thresholds, i.e., the proportion of the 
 114 

relevant social system that must engage in the behavior before the observed individual 

will join (Strange and Soule, 1988). Thresholds may vary according to the strength of ties 

with other individuals, physical proximity, or other factors (Granovetter, 1978; Valente, 

2005), which can be linked to social norm theory (Cialdini, 2003). 

Table 8: Characterizing interpersonal interaction in each social network 

Network 

Approach: Billy Woods The Noels The McAdams The Rhodes 

Diffusion Explaining how 

the PHEV differs 

from an HEV 

Telling others the 

PHEV saves trips 

to the gas station 

Explaining they 

are taking part in a 

PHEV trial. 

Detailing the fuel 

economy of the 

PHEV relative to 

their HEV. 

Conformity Perceiving that 

PHEV is not 

attractive enough 

for bar/club scene. 

Perceiving the 

PHEV as “turning 

heads,” as a “status 

symbol.” 

Seeing the PHEV 

as fairly normal in 

their social circle. 

Feeling an added 

sense of “fitting 

in” with a proenvironmental 

reference group. 

Dissemination Not observed. Not observed. Advocating 

electric-drive 

technology, and 

buying their Prius 

to promote 

production of 

green technology. 

“Spreading the 

word” about 

PHEV technology 

to improve the 

technology—also 

taught a preschool 

class on batteries. 

Translation Interpretive 

flexibility: asking 

others if cost 

savings or 

environment is 

more important 

motive for electricdrive. 

Interpretive 

flexibility: learning 

about different 

functional benefits 

of the PHEV, such 

as “less trips to the 

gas station.” 

Interpretation: 

seeing the PHEV is 

an extension of 

their Prius—proenvironment and 

supporting green 

technology. 

Interpretation: 

seeing the PHEV is 

a good way to 

reduce oil use, but 

renewable energy 

source is needed to 

make it truly 

“green.” 

Reflexivity Using the PHEV to 

learn more about a 

pro-societal 

lifestyle trajectory, 

but remaining 

more engaged and 

interested in his 

recreational 

lifestyle. 

Becoming vaguely 

aware of a prosocietal lifestyle 

trajectory, but 

remaining far more 

concerned with 

family-oriented 

living, such as 

emphasizing 

vehicle space and 

cost savings. 

Remaining fully 

engaged in a prosocietal lifestyle, 

where PHEV is 

just another stage 

of the trajectory—

supporting further 

production, but not 

as big a step as 

purchasing their 

conventional Prius. 

Remaining fully 

engaged in a prosocietal lifestyle, 

using the PHEV to 

further “spread the 

word” about green 

technology—

seeing the PHEV is 

a “stop-gap” to 

clean technology, 

and encouraging 

the next generation 

(e.g. their son). 
 115 

Examples in this study illustrate how parting from certain norms can be undesirable or 

desirable. Billy Woods describes that although he generally liked the PHEV, he thought it 

was ugly, and as a “single guy” he can’t drive around “in a car that looks like an egg.” 

Billy was not describing a particular interaction, but a general perception of the 

expectations and norms of one of his reference groups—the clubbing crowd—that a car 

should be attractive. On the other hand, the Noels’ excitedly describe how driving the 

PHEV would “turn heads” because it was a “status symbol” potentially in a sense of 

wealth as well as environmental motives. For the McAdams, driving the PHEV supported 

existing norms of their social network; Siobhan explains: “the idea of...plugging in a car 

is not that...‘Jetsons’ to our group of friends.”36 While the Rhodes expressed similar 

sentiments, Cheryl Rhodes added that relative to her SUV, driving the Prius (whether or 

not it was a plug-in conversion) made her feel “more self-righteous” when she shopped at 

a pro-environmental grocery store in her area—“like I really fit in.” 

Third, dissemination is “diffusion that is directed and managed” by an organized group 

(Rogers, 2003, p6), including processes of collective action in the provision of prosocietal goods. To date, this Project has not included any participants that are members of 

any formal groups of PHEV dissemination, e.g. Plug-in America. Further, while Billy 

Woods and Noels did describe “showing off” the PHEV in many instances, such 

interactions were not dissemination—they were more of a reaction to the novelty of the 

PHEV trial. However, the McAdams did describe themselves as advocates for electricdrive technology and Craig explained one motive for buying his Prius was to “promote 

the production of further hybrid cars.” Similarly, Larry Rhodes described how during his 

PHEV trial he would talk to others in order to “get the word out...(to) proselytize the 

eco-friendliness” of the PHEV. 

Fourth, translation defines innovations as dynamic, socially-constructed artifacts (Bruun 

and Hukkinen, 2003).37 At first, a newly introduced artifact has a high degree of 

 

36 The Jetsonswas a cartoon television show in the US first produced in the 1960s. It was set in a future of 

flying cars, robot housekeepers, levitating chairs, and other technological wonders. 

37 As used here, translation is a combination of two related sociological approaches to innovation: social 

construction of technology (SCOT) and actor-network theory (ANT). 
 116 

interpretive flexibility, where different social groups’ differing interpretations of its 

meaning and content influence further technological development (Pinch and Bijker, 

1984). Eventually the stages of interpretive flexibility reach a state of closure and 

stabilization as the perspectives of various social groups converge (Bruun and Hukkinen, 

2003) or align (Callon, 1991; Hannemyr, 2003). Participants with less electric-drive 

experience are in a state of interpretive flexibility: the Noels were coming to terms with 

the basic functions of the PHEV, and became excited when someone made the simple 

observation that it allowed them to “make less trips to the gas station” and while Billy 

Woods was quicker to understand the PHEV’s basic functions, he became interested in 

talking to others about the broader interpretations of electric drive—private, e.g., saving 

money, versus pro-societal, e.g., environmental motives. In contrast, the McAdams and 

Rhodes already had established understandings of electric-drive and alternative fuel 

technology, and saw the PHEV as further articulation of their understandings. 

Fifth, reflexivity as we use the term here is not limited to innovation, communication, or 

social influence. Giddens’ (1991) structuration approach describes personal selfdevelopment in an uncertain, social world, i.e., modernity, which lacks the set roles and 

expected behaviors enforced by tradition. Individuals must actively seek out and define 

their self-identity through “a reflexive project” (Giddens, 1991, p32). Reflexivity is the 

dynamic, continuous process of defining and expressing oneself: it moves us beyond 

assessment of the specific features of PHEV technology to focus on how individuals 

incorporate technology into their lifestyle trajectories. Reflexivity can be used to better 

understand the underlying motives of each participant, as well as integrating patterns 

described by the other perspectives. For instance, Billy Woods takes part in recreation 

and social activities he links to his interest in having an attractive vehicle. However, 

several individuals in his network are interested in other trajectories, such as green living 

and technological development. To an extent, Billy used his PHEV trial as an opportunity 

to try an alternative lifestyle trajectory and learn more about how it fit within his current 

trajectory as represented by his social network—demonstrated by his query to coworkers 

about their private versus pro-societal motives. In contrast, the Noels have far fewer 

connections with environmental and pro-societal groups, and far more integration into a 

family-oriented community, so they focus on the family aspects of the PHEV, such as 
 117 

enjoying the excitement of their children and judging they would need a PHEV larger 

than the Prius to accommodate their family. The McAdams are already fully engaged in a 

pro-societal lifestyle and see the PHEV as another step in their trajectory. The Rhodes are 

of a similar mind to the McAdams, but also link the PHEV to their family values, going 

out of their way to induce interest and support for green technology among a younger 

generation. In summary, from the perspective of reflexivity, when participants talk about 

the PHEV, they not only share information about the technology, they are also share 

information about different identities and ways of living. 
 118 

4. DISCUSSION AND CONCLUSIONS

Putting Discussion and Conclusions in Context 

The discussion presented here summarizes and interprets the preceding analyses. 

Conclusions, such as may be drawn, should be regarded as provisional and subject to 

elaboration or even contradiction as the Project continues and we learn from more 

households how they drive, recharge, and value PHEVs, and in particular, the specific 

incarnation of a PHEV they are driving. In general, we believe the behaviors we observe 

are more likely to be generalized than are the specific numerical results. 

To remind the reader of some of the important context in which the Project is being 

conducted, it is one in a series of related research tasks at the UCD PHEV Research 

Center focusing on household markets for PHEVs. In particular, one prior research 

activity was a large-sample internet-based survey of new car buyers. That survey was 

based on a nationally representative sample, with over-samples of California and northern 

California. The results from those over-samples and the participants in the present Project 

are compared where possible. Regarding the PHEVs in this study, they are conversions of 

Toyota Priuses using A123Systems’ conversion. The conversion involves the installation 

of a 5KWh (nominal) lithium-ion battery in the spare tire well and the necessary 

electrical and communications connections to incorporate the battery into the vehicle’s 

drive system and to recharge the battery. The battery charges from a standard US threeprong, grounded, 110-volt outlet. A “fully” discharged battery takes approximately five 

hours to recharge. The PHEV-conversions are still subject to the underlying architecture 

and control strategy of the stock vehicle. Notably, during CD mode, the vehicles more or 

less continuously “blend” electricity and gasoline to power the car, though using far more 

electricity in CD than CS operation. It is easier, though by no means easy, to keep the 

ICE off during CD mode in the PHEV-conversions than in a stock Prius. 

The participating households were selected, in part, because they could recharge the 

PHEV-conversions at their homes. This makes them a sub-set of all car-owning 

households and of all new-car buying households. While this makes them suitable to 
 119 

model the behaviors of other people who can recharge a PHEV at home, clearly their 

behaviors should not be simply extrapolated to the entire car market. (We judged it more 

important to learn what we can from people capable of regularly recharging a PHEV than 

to attempt to represent the entire population of car-owning households by including 

households who cannot regularly recharge at home.) 

Almost all socio-economic and demographic differences between the Project households 

(measured as a group) and the general population and the population of new-car buying 

households flow from this initial recharging capability condition. The Project participants 

are skewed toward people with higher incomes and education—even compared to our 

California and northern California over-samples. Respondents in all three of our CAbased samples are much more likely to be between the ages of 35 and 54 than the general 

population. Our Project and survey respondents are more like to live in detached homes 

than are the general population. The present gender balance of the Project participants is 

similar to that of the general US, California, and California over-sample of new car 

buying households. 

Other than these general correlations between income, education, home ownership and 

new vehicle buying, the Project households cannot be consider to be so pro-PHEV, proelectric-drive technology, or pro-environmental compared to other samples of new car 

buyers as to skew their reports in favor of PHEVs. The Project sample contains a slightly 

higher percentage of people who state that air quality, climate change and oil dependence 

are “serious problem[s], and immediate action is necessary” than in the California and 

northern California over-samples. Still the differences are small and we judge them to be 

unlikely to make a substantive difference to any conclusions we may draw between the 

samples on PHEV designs created by participants in their design games. 

There is little to distinguish the knowledge of electric drive vehicles of the Project 

participants from the survey respondents—except on the specific issue of plug-in hybrids. 

Across all samples, very high percentages of respondents know that a plug-in hybrid can 

be both fueled and plugged-in; the highest percentage is among our Project participants. 

There are a few opportunities for “information leaks” about PHEVs to respondents in the 
 120 

present Project: the recruiting phone call and the information unavoidably provided to 

households when the PHEV is first delivered. (The questions about electric-drive 

knowledge are part of a longer, more substantive questionnaire that cannot be 

administered until after the household is fully enrolled in the Project, which occurs when 

the vehicle is delivered.) 

Most Project participants faced lower gasoline prices during their PHEV trial month than 

did the prior survey respondents. However, the first Project participants were paying well 

in excess of $4.00 per gallon for gasoline in August 2008. Whether they faced higher 

gasoline prices during their PHEV trial period or whether they simply recall such higher 

prices from last summer, we expect that all other Project participants may be more 

sensitive to the uncertainty of gasoline prices than the national and California survey 

respondents. This may make Project participants less like our prior survey respondents, 

but more like their peers, i.e., all present day car-buying households who have lived 

through this same history of gasoline prices. 

Assessing PHEV Purchase Intentions and Design Priorities 

We assess the interest of respondents in buying PHEVs—and which PHEVs—through a 

series of design games. The games rely on two different contexts and have two different 

goals. One explores what is interesting and valuable to respondents about PHEVs per se. 

The other more directly addresses the question of interest in buying a PHEV. We limit 

our conclusions about PHEV designs to the subset of respondents who can recharge a 

vehicle at home (which includes all Project participants) and demonstrate a PHEV 

purchase intention in the highest price version of the PHEV design games. 

It (still) isn’t about all-electric driving; it’s about fuel economy 

In summary, in the Project to date we find more evidence to support our prior conclusion 

from the national survey that consumers create PHEV designs that emphasize (gasolineonly) fuel economy and, conversely find no evidence to contradict our prior finding of 

low demand at present for PHEVs offering all-electric operation in CD mode. Most 

respondents in both studies and across both design games designed PHEVs based on 
 121 

blended operation in CD mode. In effect, they designed PHEVs that emphasized 

improvements in (gasoline-only) fuel economy over designs that emphasized all-electric 

driving. While it is possible that the Project participants PHEV designs were “anchored” 

by their driving a blended-mode PHEV that does not easily provide all-electric operation 

throughout its CD range, it is still the case that experience with a PHEV has not led our 

Project participants to be more likely to emphasize all-electric CD operation than our 

prior survey respondents who had no PHEV experience. This conclusion is further 

supported by the relatively greater emphasis that respondents across all samples placed 

on improving the fuel economy of the vehicle in CS operation than in either dimensions 

of CD performance: all-electric (vs. blended) operation and longer CD driving range. 

Further, only a tiny subset combined both all-electric driving and 40 miles CD range (the 

longest CD range offered in the games) 

Project results do differ from survey results in some important ways 

Project participants who had driven a (blended-operation) PHEV for a month were more 

likely than the previous survey respondents to 1) design a PHEV they are interested to 

buy rather than opt to buy a conventional vehicle, 2) design a PHEV that had better 

PHEV performance than the base PHEV design offered to them, and 3) to chose an HEV 

as the base vehicle they considered for redesign as a PHEV. Still, these differences are at 

the margin, and the overall conclusions one draws from the Project participants are 

similar to those we drew from the survey. The Project does appear to have a slightly 

greater persuasive effect of convincing participants that a PHEV is a worthwhile and 

desirable vehicle for their household, as well as an effect of convincing them that an HEV 

is a worthwhile vehicle for their household. Given that they have designed a PHEV they 

want, few Project participants were interested in faster recharging times than the base 

offering of eight hours—recall, all these households were selected to participate in the 

Project in part because they can recharge a vehicle at home. Project participants are more 

likely than survey respondents to improve CD mode—both operating mode and range. 

Yet as noted above, the slightly higher prevalence of all-electric designs compared to 

previous survey samples (~five percent in the Project compared to ~one percent in the 

survey) does not overrule the larger conclusion that only a small minority of new car 
 122 

buyers presently value all-electric PHEV designs. There is little difference between 

samples in the probability to improve CS fuel economy performance—in large part 

because this is the most common attribute to be improved by respondents in all samples. 

These findings contrast with the earlier findings of Kurani et al.’s (2007) interviews with 

“pioneer” PHEV conversion drivers who exhibited strong interest in maximizing CD 

range in all-electric mode—effectively approaching the capabilities of pure electric 

vehicles. This difference suggests that while all-electric CD operation may presently be 

attractive to a small subset of consumers including those who are already knowledgeable 

and experienced with electric vehicles, at this point in time most households who buy 

new vehicles are more interested in high fuel economy, even after completing a multiweek trial with one (blended) PHEV incarnation. 

If it’s not about all-electric driving now, can it be in the future? 

The wide variety of PHEV designs created by survey respondent and Project participants 

supports the conclusion that the car-buying pubic has widely varying, and perhaps as yet 

unformed, PHEV performance expectations. Their desired PHEV designs and capabilities 

may be subject to change. Project participants and survey respondents had little preexisting understanding of PHEVs and the responses we elicited may be sensitive to the 

PHEV information we provided. As information about PHEV technology, costs, benefits, 

and meanings are transmitted throughout the population, interest in PHEV attributes and 

performances could shift. For example, all-electric CD operation could become more 

meaningful to car buyers as they gain experience with all-electric operation and as they 

participate in the process of identifying just what all-electric operation means to people. 

In the meantime, this analysis provides a baseline of market potential—one that could be 

subject to influence. The messages and actions of policymakers, automakers, electric 

utilities, and other interest groups could have significant influence over future 

development of PHEVs. 
 123 

Charging and refueling behaviors 

Recharging: How often, where, and when 

As outlined in the introduction to this report, the benefits of PHEVs compared to 

conventional vehicles, HEVs, and battery EVs depend on recharging behavior. There 

may be no more fundamental question about PHEVs than whether or not people will 

plug-in a vehicle that does not have to be plugged-in. The answer from the Project 

participants to date is, “Yes, we will.” The households who have participated in this 

Project, on average, plugged-in these PHEV-conversions about once per day, and did so 

more often on weekdays than weekend days. There was large variation in the mean 

frequency of PHEV recharging across households—from zero to 2.6 times per weekday 

and zero to 1.5 times per weekend day. Higher frequency of plugging-in on weekdays is 

associated with 1) recharging at work during the workday, and 2) recharging at home 

during the day by retired households. The frequency of plugging-in on weekend days was 

also lower than on weekdays because the PHEVs were more likely to be away from 

home, and thus away from the households’ primary or sole recharging location. Only a 

few households found away-from-home recharging locations they used on a regular basis. 

These were associated with trips to work; the electrical outlets were either in the 

employers’ parking lots or public parking garages. 

By the end of their PHEV trial, if the participants understood how to maximize the use of 

the supplemental battery, they were recharging every night (that the vehicle was home). 

Those who did not understand the state of charge of the battery, or the PHEV technology 

in general, did not necessarily recharge nightly or, in some households in any apparent 

pattern. When asked about recharging, most participants discussed the actual act of 

plugging into the electrical outlet but not the frequency with which they recharged. 

Despite the fact that most households asked us about how often to recharge when the 

PHEV was first delivered to them, it appears that recharging either 1) quickly became a 

daily routine or chore—irrespective of the level of understanding of why they would plug 

the car into the grid—or 2) that differences in the performance of the PHEV in CD and 
 124 

CS mode were not adequately represented to some households for them to understand 

why and when to recharge the car. 

In general, most households plugged in their PHEVs after 4:00pm on weekdays and left 

them plugged in until 6:00am the next morning. While the weekday electricity demand 

from vehicles being plugged in between 5:00pm and 6:00pm creates a rapid increase in 

grid electricity demand, the differences between “availability,” i.e., when the vehicle is 

plugged-in to the grid, and “demand,” i.e., when the vehicle draws electricity from the 

grid to recharge the battery, show there is opportunity to shift electricity demand for 

PHEV recharging to presently existing off-peak electricity demand periods for these 

households (and vehicles). Weekend days present even greater opportunity to manage 

grid power to the vehicles since 1) fewer vehicles are plugged in, 2) those vehicles that 

are plugged in require less electricity to fully recharge, and 3) those vehicles that are 

plugged-in tend to remain plugged in longer into the next morning. 

While off-peak recharging of PHEVs would be advantageous to electricity providers, it 

could produce other benefits, such as reduced carbon content of the electricity used to 

recharge electric-drive vehicles, given that most wind power is produced during the night. 

Hence, off-peak charging, or even control over the type of electricity used to recharge 

electric drive vehicles, could significantly decrease the carbon emissions of the electricity 

used to power electric drive vehicles, thus providing greater transportation related GHG 

reductions. However, the construction of new renewable energy resources that operate 

primarily during present off-peak electricity demand periods competes with electricity 

providers goal (and one of the oft cited reasons to promote electrifying transportation) to 

increase the value of sunk investments in existing power production through increasing 

capacity factors. 

It is important to emphasize that individual household’s charging behavior, vehicle use, 

and vehicle performance varied across days, recharging intervals, and trips. In an effort to 

demonstrate the different ways households could plausibly use these vehicles, we 

disaggregated the PHEV trial of the Kermode family and constructed an alternate month 

based on their interview data. The two months—the month as measured in the Project 
 125 

including multiple, away-from-home weekend tours and 2) a constructed month that 

substitutes measures of their in-town weekend travel for the longest of these tours—

provide descriptions within which most of the Kermodes’ vehicle use is likely to fall. 

Depending on which month and which comparative vehicle(s) one references, the 

improvement resulting from the substitution of the PHEV-conversion into the Kermodes’ 

life on the gasoline-intensity of their travel is bounded by estimates of ten to 180 percent. 

Total Energy, with and without recharging 

We compared the total energy (gasoline plus electricity) used by the households to drive 

the PHEV-conversions for their four-week trial to the gasoline they would have used had 

they not recharged at all. This is a close approximation to the question, “What difference 

does it make that this PHEV-conversion can be plugged into the electrical grid?” The 

gasoline displaced by electricity ranges from one to 19 percent of the gasoline that would 

have been consumed if the households had not recharged at all. This is not the same as 

the question of what difference it might make if any of these households would buy, 

drive, and recharge a plug-in vehicle rather than continue to drive any of their existing 

household vehicles or buy and drive any other conventional (or hybrid) vehicle they 

might buy. 

Recharging causes differences in total energy use through the frequency of recharging, as 

moderated by the (mis)match between households’ travel distances per recharging 

interval and their achieved CD range. Those households who closely match their travel to 

their achieved CD range of these PHEV conversions are able to achieve a much higher 

percent of their travel in CD mode (70 to 80 percent) and thus greater percentage energy 

(gasoline plus electricity) reductions through the substitution of electricity for gasoline 

(17 to 19 percent). These households achieve higher percentages of CD mode driving 

because either their common daily travel is less than their achieved CD range or they had 

access to away-from-home (and in this case, workplace) recharging so that they 

recharged multiple times per day. 

Households are not uniform across their own four-week PHEV trial as to this match to 

their achieved CD range. A household such as the Kermodes accomplished most travel 
 126 

days within their CD range. But their aggregate (gasoline-only) fuel economy, percent 

miles driven in CD operation, and gasoline displacement were among the worst of the 

Project participants to date because of a few multi-day tours out of town. Again relying 

on all the data available to us though, especially from the interviews, a month can be 

constructed that is similar to many months of the Kermodes’ lives. In this constructed 

month, their performance is much closer to the norm of the other Project participants, 

including an increase in aggregate (gasoline-only) fuel economy from 49 to 55mpg, 

percent miles driven in CD operation from 22 to 36 percent, and percent gasoline 

displaced from 4 to 13 percent. 

Such analysis of total energy is entirely a construction of the analysts—no household has 

created an integrated accounting of both their gasoline and electricity use. Not even those 

few households who have used the V2Green website which contains measures of 

gasoline and electricity use and estimates of costs for both have any idea how much 

electricity they are using or what it is costing them. A few households have remarked 

how hard it is to see their electricity use through their monthly utility bill. As one 

households who tried remarked, changes in weather that caused them to begin to use their 

air conditioning during their PHEV trial month meant they could not figure out how 

much their higher electricity bill was due to their AC or the PHEV. 

Recharging Habits and Etiquette: Infrastructure isn’t the only barrier 

From the narrative analysis, we learned that most households spoke about recharging 

becoming part of their daily routine, similar to recharging a cell phone or feeding the dog. 

For a few households, the task took on the slightly negative connotation of “chore” rather 

than a habit or routine. But the majority of the Project participants said plugging-in the 

PHEV was easy and not a hassle. (The exception was the extension cord—almost 

universally households observed that a retractable cord would be a welcome design 

change.) Most people recharged at home because of the time needed to recharge the 

battery, availability of an electrical outlet, and safety of the car (and cord). Most stated 

that recharging at night was ideal because they could plug-in the car when they got home 

and un-plug it in the morning before heading to work. Several were concerned about 
 127 

plugging in their car if it was parked outside of their garage for fear of a tripping hazard 

or someone stealing the cord. 

Some looked for recharging at local malls, job sites, or during out of town trips; none 

found it easy to locate an appropriate outlet. Many situations in which people did not 

recharge away from home can be interpreted as a lack knowledge about the of etiquette 

regarding recharging behavior: people were unsure if asking to plug in would be seen as 

rude or presumptive. Several participants specifically related that they did not ask to 

recharge at the houses of friends or family because they were unsure whether it was 

appropriate. 

It can also be said that it is not merely the lack of knowledge by the Project drivers of 

recharging etiquette, but the lack of a set of social norms and rules altogether. Electric 

vehicle drivers in California in the 1990s did develop some informal rules about sharing 

the limited number of public EV recharging locations. But those EV drivers were too 

small a group to have created a set of more widely recognized and accepted social norms 

regarding the use of electrical outlets over which the driver does not have sole control, 

e.g., at home. Ironically, in and around the cities of Sacramento and Davis, CA the 

lingering presence of public EV parking and recharging facilities caused discussion and 

confusion on the part of some Project participants who recalled hearing about or seeing 

such facilities. Those who actually sought out this EV infrastructure were disappointed to 

find it did not have the appropriate electrical outlet for their PHEV. While some of these 

Project drivers questioned whether they were allowed to park in these EV spaces, others 

simply assumed they were allowed. 

No One Misses Refueling with Gasoline 

We have not presented analyses of gasoline refueling behavior in this report. 

Summarizing discussions with Project households, the long-refueling intervals of the 

PHEVs are noted by almost all households. The PHEVs are routinely refueled much less 

often than the households’ own vehicles for which the PHEV substitutes. This is 

sometimes an important marker for a household—eliciting delight and amazement at the 

long-periods of times between trips to gasoline stations. For some people, this experience 
 128 

was positive, but did not solve any problem (other than paying for gasoline!). For other 

people though, the reduction in trips to gasoline stations was more than a novelty. As we 

have observed in other research (Kurani and Turrentine, 1996; Turrentine and Kurani, 

2007), some people identify gasoline stations as dangerous or dirty locations. We note no 

other reports of changes in refueling behavior. People did not believe they had bought gas 

at different stations, nor at different points in their daily routines; at least, no such 

changes were so remarkable that households could recall them. 

Driving behaviors 

We treat driving behaviors at two scales. The first is a daily-to-monthly scale at which 

measures such as the households’ percent of miles driven in CD mode is one summary of 

the relationship between households driving and recharging behavior. The second is at a 

shorter time scale—within a single trip—where we explored how the vehicle and 

information interfaces may have changed how people drove. 

Summary Measures of Driving and Recharging 

As discussed in the opening of this report, the potential energy and environmental effects 

of PHEVs flow from the amount of electricity that displaces gasoline. This in turn 

depends on the relationship between PHEV designs and capabilities on the one hand, and 

PHEV drivers’ driving and recharging behaviors on the other. The percentage of miles 

driven in CD mode is one measure of how all three interact. 

One way to measure the performance of a particular technical specification for a PHEV is 

to recast it in terms of the realized performance based on our participants’ driving and 

recharging behaviors. In this way the vehicle used in this project can be described as: 

1. A PHEV that operates in blended mode during CD operation; 

2. During which it will return (21 to 101) percent better gasoline-only fuel economy 

than it otherwise achieves in CS operation; 

3. CD operation will last for (25 to 35) miles using a definition of CD range that 

references only when the switch from CD to CS operation occurs; 
 129 

4. In exchange for about 4KWh of grid-electricity; and, 

5. Achieves (38.0 to 51.5mpg) in CS operation (where percent improvement in CD 

operation is positively correlated with CS fuel economy across drivers). 

The ranges of CD and CS performance values above are explained in part by differences 

in aggressiveness of accelerations, top speeds, mixes of driving on surface street vs. 

freeway, amenability to playing energy conservation games through the information 

interfaces, and travel and recharging behavior affecting the match between miles driven 

per recharging interval and each driver’s realized CD range. One measure to encapsulate 

all of this is the percent of miles driven in CD operation. The particular vehicles used in 

this Project were driven, on average across the households’ four-week trials, in CD 

operation for 53 percent of their total miles; the range across household means was 17 to 

81 percent. It is unsurprising, but important, that the range within a single household 

across their recharging intervals can be greater, e.g., from less than two percent to 100 

percent in one household. 

Changing Driving Behaviors through User Interfaces 

It is impossible at this time to generalize the impact of in-vehicle and internet-based 

information interfaces on fuel economy as each participant interacted with the available 

vehicle information in a different way. Some participants completely ignored the 

information; others found the information to be a stimulating and engaging learning tool. 

We can speak about the causes of these differences. Some of the major reasons seem to 

be prior interest in fuel economy (interest in fuel economy changed and often increased 

over the course of the study), technological fluency, and each participant’s role within 

their household in regards to vehicles or technology. 

From the themes identified through the narrative analysis, we propose a few basic lessons 

that may help future interface designs to facilitate greater effects on energy use: 

• The closer the information is to the point of interest, i.e. in the car vs. on the home 

computer, the more likely it is that the information will be used. 
 130 

• Simplicity in representation and interpretation is critical to driver understanding. 

• The interface should support drivers in setting and achieving goals by providing 

relevant summary information. 

• Instantaneous Fuel Economy can provide drivers with erroneous information, 

especially during braking events. 

• Whenever possible, information should be presented in a grounded context so that 

drivers can quickly understand the relative impact of their behavior. 

Although these general lessons are by no means definitive or complete, they represent a 

simplified interpretive summary of the many participants’ responses to the interfaces 

included in this study and as the basis for the design of ongoing research to elaborate and 

specify these lessons. 

Narrative Themes: Confusion and Payback 

Narrative synthesis and analysis plays a confirmatory and explanatory role regarding 

recharging and driving behaviors discussed already. Two additional themes that emerged 

from the household narratives are further discussed here: confusion about PHEVs and the 

use of a payback analysis to assess PHEVs. 

Confusion 

Most Project participants were initially confused by the idea of a PHEV. Some remained 

unfamiliar and uncomfortable with the PHEV technology even after they had spent a 

month with the vehicle. A few households believed that recharging the car would 

increase fuel-only economy, but did not really understand how. Most of the households 

were confused about the state of charge of the battery. This—combined with 

inappropriate mental models of how batteries work—caused some participants to 

recharge less frequently than they would have if they had known how to determine the 

state of charge for the battery and if they had understood what the benefits might be. 

Households cited the example of their cellular phone’s battery—so long as it had some 
 131 

charge, they derived full value from the phone calls made or received on it. The Project 

shows the extent to which experience and instrumentation can assist some households to 

develop more refined understandings of PHEVs, and that more needs to be done. 

Valuing PHEVs: Payback and Intuition 

Many households discussed using some form of a cost-benefit analysis to determine 

whether the PHEV was “worth it.” Most of these households discussed simple payback 

analysis comparing a purchase price and operating cost differences. A few households 

discussed more sophisticated net present value calculations. No households appear to 

have completed either simple payback or net present value calculations, most households 

made mistakes in describing how to make such calculations and demonstrated they did 

not know the values of all the costs and benefits that would enter into such a calculation. 

In contrast, some households offered an intuitive assessment. Octavia, for example, said 

that using less gas “was a great feeling” because it “has got be a good thing.” She linked 

gas savings with energy independence and reducing environmental impacts. She said that 

in the world today “we have people dying...corruption and big business...due to the 

whole dependence on oil...we are in trouble...” creating “untenable situations for our 

country”; “we can’t keep going this way.” Octavia felt that PHEV instrumentation would 

help people make a stronger connection between their personal actions and such global 

problems. For her, this awareness was a large benefit to driving a PHEV. She figured that 

most current HEV buyers were driven by financial motives, whereas if she were to buy 

an HEV, it would be for environmental reasons. She believed that climate change is a 

real, human-caused problem that, along with air pollution and the nation’s dependence on 

foreign oil, requires urgent action. She sees owning a PHEV as part of the solution. 

Social Influence 

We observe the almost complete lack of attention in prior analyses of electric-drive 

vehicles to the importance of social networks. The few examples cited in this report are 

suggestive of the additional understanding of how market, technology, and policy 

processes can be affected by understanding that not only are new vehicles, e.g., PHEVs, 
 132 

socially constructed, but so too are the processes in which they are developed, marketed, 

regulated, and used. In this Project, we are focusing on how our participating households 

construct and communicate their understanding and experience of PHEVs through their 

interactions within their social networks. This aspect of the Project has been deployed in 

only a few households to date, but will continue with the rest of the Project. 

The first question within this social network research task is whether interpersonal 

interactions play a significant role in the assessment and adoption of electric-drive 

vehicles. We have observed that social interactions are influential for primary households 

(the Project drivers and households) and secondary respondents (selected members of the 

primary households’ social networks). The second research question explores and 

characterizes specific processes of social interactions. We described these interactions 

from five perspectives: contagion, conformity, dissemination, translation, and reflexivity. 

Five Approaches to Describing Social Interactions 

Contagion describes social interactions as point-to-point communication of information. 

The concept includes diffusion of innovations (DOI). Our preliminary assessment is that 

the idea of contagion neglects many of the subtle but important nuances of interpersonal 

influence, such as why particular types information are selected to share, why particular 

types of information are remembered by the listener, and how such information is 

interpreted in various contexts. Further, the notion that information diffuses in one 

direction, from innovators toward the majority, appears limiting. We observe households 

and their social networks that did not draw their perceptions from an “innovator.” Rather, 

they formed a general understanding of the PHEV through an ongoing discourse of social 

interactions that they integrated with their existing knowledge. 

Conformity focuses on individual’s perception of social norms and the actions of others. 

This study reveals examples of ways in which the PHEV-conversion—or in some cases, 

the base Prius on which it is based—conforms or fails to conform to social norms of 

some groups with the participants’ social networks. Our primary respondents are left the 

task of reconciling (or not) the extent to which this new idea, a PHEV, conforms to the 

social norms that shape other aspects of their lives. Personally, that is to the individuals 
 133 

within the Project households, conformity may be important, but the fact the PHEV may 

conform to their social networks’ norms does not appear to stimulate more social 

interaction. 

Dissemination is “diffusion that is directed and managed” by an organized group. To 

date, the Project has not included any participants that are members of a formal group 

attempting to disseminate PHEVs, e.g. Plug-in America. However, two households have 

demonstrated informal efforts to disseminate information about the pro-societal benefits 

of electric-drive vehicles within their social networks. 

Translation defines innovations as dynamic, socially-constructed artifacts (Bruun and 

Hukkinen, 2003). A newly introduced artifact has a high degree of interpretive flexibility: 

different social groups’ differing interpretations of its meaning and content influence 

further technological development (Pinch and Bijker, 1984). Project participants with less 

prior electric-drive knowledge and experience are in a state of interpretive flexibility, still 

coming to terms with even the basic functions of a PHEV. In contrast, participants with 

more electric-drive knowledge and experience are approaching a state of closure or 

stability, in which the meanings of PHEVs are less flexible, less susceptible to change. 

Reflexivity as discussed within Giddens’ (1991) structuration approach moves us beyond 

assessment of specific features of PHEVs to how individuals incorporate technology into 

their lifestyle trajectories. Within this approach, reflexivity can be used to better 

understand the underlying motives of each participant, as well as integrating patterns 

described by the other perspectives. We observed participants view their PHEV trial as an 

opportunity to try an alternative lifestyle trajectory, for example the young man who 

“tried on” his friends and co-workers environmental values through his participation in 

the PHEV research In other households, we observe how the PHEV is evaluated in terms 

of its ability to further an existing lifestyle trajectory, whether that be the high value of 

children or a pro-societal lifestyle calculated to induce interest and support for green 

technology. From the perspective of reflexivity, when participants talk about the PHEV, 

they not only share information about the technology, they are also share information 

about different identities and ways of living. 
 134 

In summary, preliminary results suggest that interpersonal interactions within social 

networks play an important role in shaping the assessment of these PHEV conversions, 

and likely electric-drive vehicles more generally. Diffusion, conformity, and 

dissemination provide useful concepts for particular processes, but translation and 

reflexivity appear to best provide the language and theoretical depth required to integrate 

the various motives and perceptions observed among participating social networks. 

However, before conclusions can be drawn, more networks need to be explored and 

further analysis is required. 

Looking Forward 

The UC Davis PHEV Research Center will continue the Project through at least the end 

of 2009, and possibly through the first quarter of 2010. Extensions beyond that time will 

be pursued especially if opportunities to incorporate different types of PHEVs into the 

Project can be negotiated. The goals of extending the Project in its present form are to 

increase the number of participating households, extend and refine the application of 

narrative, conduct an additional set of research activities around driver feedback, and 

continue the study of the effects of social interactions on the spread of information about 

PHEVs. Regardless of any future opportunity to incorporate additional types of PHEVs, a 

final omnibus report similar to this one will be issued on households experience with 

these PHEV-conversions comparing and contrasting the early and later results. In 

addition, separate focused articles will be prepared on specific topics derived from each 

of the main findings sections of this report. 
 135 

REFERENCES

Axsen, J. and K. S. Kurani (2008). The Early U.S. Market for PHEVs: Anticipating 

Consumer Awareness, Recharge Potential, Design Priorities and Energy Impacts. 

Institute of Transportation Studies, University of California, Davis, University of 

California, Davis, Research Report UCD-ITS-RR-08-22. 

Axsen, J., A. Burke, and K. Kurani (2008). Batteries for plug-in hybrid electric vehicles 

(PHEVs): Goals and the state of technology circa 2008. Institute of Transportation 

Studies, University of California, Davis, Research Report UCD-ITS-RR-08-14. 

Berger, Ronald J. and Quinney, Richard. (2005). The Narrative Turn in Social Inquiry. 

Storytelling Sociology: Narrative as Social Inquiry. Lynne Reinner Publishers: 

Boulder, Colorado. 

Brown, M. B. (2001). The civic shaping of technology: California's electric vehicle 

program. Science Technology & Human Values, 26(1): 56-81. 

Bruun, H. and A. Hukkinen (2003). Crossing boundaries: An integrative framework for 

studying technological change. Social Studies of Science, 33(1): 95-116. 

Bunch, D., M. Bradley, T. Golob., R. Kitamura, and G. Occhizzo (1993). Demand for 

clean-fuel vehicles in California: A discrete choice stated preference survey. 

Transportation Research A, 27, 237-253. 

California Air Resources Board – CARB (2003). California Exhaust Emission Standards 

and Test Procedures for 2005 and Subsequent Model Zero-Emission Vehicles, and 

2002 and Subsequent Model HEVs, in the Passenger Car, Light-Duty Truck and 

Medium-Duty Vehicle Classes.” Sacramento, CA: California Environmental 

Protection Agency. 

California Air Resources Board – CARB (2008a). ARB Passes New ZEV Amendment: 

Measures could produce 65,000 cleaner vehicles by 2012, Press Release, March 
 136 

27th, 2007, http://www.arb.ca.gov/newsrel/nr032708b.htm (accessed April 17th, 

2008). 

California Air Resources Board – CARB (2008b). 2008 Proposed Amendments to the 

California Zero Emission Vehicle Program Regulations, Staff Report: Initial 

Statement of Reasons, February 8th, 2008, 

http://www.arb.ca.gov/regact/2008/zev2008/zevisor.pdf (accessed April 17th, 

2008). 

Callon, M. (1991). Techno-economic networks and irreversibility. A Sociology of 

Monsters: Essays on Power, Technology and Domination. J. Law. Routledge: 

London. 

Canzler, W. (1999). Changing speed? From the private car to CashCar Sharing. SPEED -

A workshop on space, time and mobility. Copenhagen, Denmark: The Danish 

Transport Council. 

Carrasco, J. A., B. Hogan, et al. (2008). Collecting social network data to study social 

activity-travel behavior: an egocentric approach. Environment and Planning B: 

Planning and Design, 35(6): 961-980. 

Cialdini, R. B. (2003). Crafting normative messages to protect the environment. Current 

Directions in Psychological Science, 12(4): 105-109. 

Degenne, A. and M. Forse (1994). Introducing Social Networks. London, SAGE 

Publications. 

Duvall, M., et al. (2002). Comparing the Benefits and Impacts of Hybrid Electric Vehicle 

Options for a Compact Sedan and Sport Utility Vehicles, EPRI, Palo Alto, CA: 

2002, Report #1006892. 

Ewing, G. and E. Sarigollu (2000). Assessing consumer preferences for clean-fuel 

vehicles: A discrete choice experiment. Journal of Public Policy and Marketing, 19, 

106-118. 
 137 

Gondor, J. and A. Simpson (2007). Measuring and Reporting Fuel Economy of Plug-In 

Hybrid Electric Vehicles, WEVA Journal, Vol.1. 

Giddens, A. (1991). Modernity and Self-Identity: Self and Society in the Late Modern 

Age. Stanford, CA, Stanford University Press. 

Gjoen, G. and M. Hard (2002). Cultural politics in action: Developing user scripts in 

relation to the electric vehicle. Science Technology & Human Values, 27(2): 262-

281. 

Granovetter, M. (1973). Strength of weak ties. American Journal of Sociology, 78(6): 

1360-1380. 

Granovetter, M. (1978). Threshold models of collective behavior. American Journal of 

Sociology, 83(6): 1420-1443. 

Green, D. P. (1992). The price elasticity of mass preferences. American Political Science 

Review, 86(1): 128-148. 

Hannemyr, G. (2003). The Internet as hyperbole: A critical examination of adoption 

rates. Information Society, 19(2): 111-121. 

Heffner, R. R. (2007). Semiotics and Advanced Vehicles: What Hybrid Electric Vehicles 

(HEVs) Mean and Why it Matters to Consumers. Institute of Transportation Studies. 

Davis: CA, University of California, Davis. PhD. 

Heffner, R., K. Kurani, and T. Turrentine (2007). Symbolism in California’s early market 

for hybrid electric vehicles. Transportation Research Part D, 12, 396-413 

Herman, L. and B. Vervaeck (2005). Handbook of Narrative Analysis. Board of Regents 

of the University of Nebraska. 

Hirschman, E. C. (1981). Symbolism and Technology as Sources for the Generation of 

Innovations. Advances in Consumer Research, 9: 537. 
 138 

Hogan, B., J. A. Carrasco, et al. (2007). Visualizing Personal Networks: Working with 

Participant-aided Sociograms. Field Methods, 19(2): 116-144. 

Kalhammer, F.R., B.M. Kopf, D. Swan, V.P. Roan, and M.P. Walsh (2007). Status and 

Prospects for Zero Emissions Vehicle Technology: Report of the ARB Independent 

Expert Panel 2007, Prepared for State of California Air Resources Board, 

Sacramento, California, April 13 2007. 

Kromer, M. and J. Heywood (2007). Electric Powertrains: Opportunities and Challenges 

in the U.S. Light-Duty Vehicle Fleet, LFEE 2007-03 RP. Sloan Automotive 

Laboratory, Massachusetts Institute of Technology, Cambridge, MA. 

Kurani, K., R. Heffner and T. Turrrentine (2007). Driving Plug-In Hybrid Electric 

Vehicles: Reports from U.S. Drivers of HEVs Converted to PHEVs, Circa 2006-

2007, Institute of Transportation Studies, University of California, Davis, October 

16th, 2007. 

Kurani, K., T. Turrentine, and D. Sperling (1996). Testing electric vehicle demand in 

‘hybrid households’ using a reflexive survey, Transportation Research Part D,

1(2), 131-150. 

Lieblich, A., R. Tuval-Maschiach, and T. Zilber. (1998). Narrative Research: Reading, 

Analysis, and Interpretation. Applied Social Research Methods Series. Vol 47. 

Markel, T. et al. (2006), Plug-in hybrid vehicle analysis, Milestone Report, National 

Renewable Energy Laboratory, NREL-MP-540-40609, November, 2006, 

http://www.nrel.gov/, accessed on 2008-09-22. 

McCracken, G. (1988). The Long Interview. Newbury Park, California, Sage 

Publications. 

Pesaran, A., T. Market, H. Tataria, and D. Howell (2007). Battery Requirements for PlugIn Hybrid Electric Vehicles: Analysis and Rationale, 23rd International Electric 

Vehicle Symposium and Exposition (EVS-23), Anaheim, California, December 2-5, 

2007. 
 139 

Pinch, T. J. and W. E. Bijker (1984). The social construction of facts and artifacts - Or 

how the sociology of science and the sociology of technology might benefit each 

other. Social Studies of Science, 14(3): 399-441. 

Potoglou, D. and P. Kanaroglou (2007). Household demand and willingness to pay for 

clean vehicles, Transportation Research Part D, 12, 264-274. 

Reissman, C. K. (1993). Narrative Analysis. Qualitative Research Methods Series 30. 

Sage Publications: Newbury Park, California. 

Rogers, E. (2003). Diffusion of Innovations (5th Ed.). New York, Free Press. 

Schram, S.F. and P.T. Neisser (1997). Introduction. Tales of the State: Narrative in 

Contemporary U.S. Politics and Public Policy. Rowman and Littlefield Publishers, 

Inc: Lanham, Maryland. 

Strang, D. and S. A. Soule (1998). Diffusion in organizations and social movements: 

From hybrid corn to poison pills. Annual Review of Sociology, 24: 265-290. 

Turrentine, T. S. and K. S. Kurani (2007). Car buyers and fuel economy? Energy Policy, 

35(2): 1213-1223. 

Valente, T. (2005). Network Models and Methods for Studying the Diffusion of 

Innovations. Models and Methods in Social Network Analysis. P. Carrington, J. 

Scott and S. Wasserman. New York, New York, Cambridge University Press: 98-

116. 
 140 

ACRONYMS AND GLOSSARY

All-Electric Operation: Operation in charge-depleting (CD) mode that uses only grid 

electricity, rather than electricity produced by an on-board generator, to power the 

vehicle. 

Blended Operation: Operation in charge-depleting (CD) mode that uses grid electricity 

and gasoline to power the vehicle; energy from both are “blended” together through 

the electro-mechanical drivetrain. 

Charge Depleting (CD) Mode: Energy stored in the battery is used to power the vehicle 

by gradually depleting the battery’s state of charge (SOC) (see “Charge 

Sustaining”).

CD Range: The distance a PHEV can drive in charge depleting (CD) mode before 

switching to charge sustaining (CS) mode. (Other definitions include 1) the 

equivalent distance that could be traveled on electricity given on-board storage, and 

2) the distance traveled before the ICE first turns on. The last is relevant to series 

PHEV designs and is equivalent to “all-electric range.”) 

Charge Sustaining (CS) Mode: The battery’s state of charge (SOC) is sustained by 

relying primarily on the gasoline engine to drive the vehicle, only using the battery 

and electric motor to increase the efficiency of the gasoline engine, as is done in an 

hybrid-electric vehicle (HEV).

(Usable) Depth of Discharge (DOD): The differences between the battery’s maximum 

and minimum states of charge (SOC); usually less than 100% in practice. 

Electricity availability: The time of day vehicles are plugged-in to an electrical outlet 

Energy Density (Wh/kg): The amount of energy stored per kg of a battery pack or cell. 

Electric Vehicle (EV): An electric drive vehicle that is only powered by grid electricity. 
 141 

Hybrid Electric Vehicle (HEV): A vehicle primarily powered by a heat engine (e.g. an 

internal combustion engine), but uses an electric motor and energy storage system 

(e.g. an advanced battery) to improve the efficiency of the engine’s operation. 

Kilowatt (kW): A measure of power (1000 watts), where 1 kW = 1.34 horsepower. 

Kilowatt-hour (kWh): A measure of energy use or capacity, where 1 kWh = 1,000 Watts 

provided for 1 hour. 

Parallel Architecture: A PHEV drivetrain that allows a direct connection between the 

engine and the wheels, as well as between the engine and battery and motor via a 

generator. The vehicle can be powered by electricity and gasoline simultaneously, 

electricity only, or by gasoline only. The battery is charged from an electrical outlet, 

or by the gasoline engine via a generator. 

Plug-In Hybrid Electric Vehicle (PHEV): An electric drive vehicle that can be powered 

by a heat engine (e.g. an internal combustion engine), an electric motor using grid 

electricity (e.g. stored in a battery), or both. 

Power Density (W/kg): The amount of power that can be provided per kg of battery pack

or cell.

Series Architecture: A PHEV drivetrain that powers the vehicle only by an electric 

motor using electricity from a battery. The battery is charged from an electrical 

outlet, or by the gasoline engine via a generator (e.g. GM’s Volt concept) 

State of Charge (SOC): The ratio of energy currently stored in a battery to the battery’s 

maximum capacity. 

Total Energy Capacity: The amount of total energy (in kWh or kWh/kg) that can be 

stored in a battery. Not all of this energy is usable, as operation is limited to using 

the assigned depth of discharge (DOD) to preserve battery life and safety. 

Zero Emission Vehicle (ZEV): A vehicle that produces zero tailpipe emissions. 
 142 

APPENDICES

Appendix A: Household Final Interview Protocol 

Appendix B: PHEV Buyers’ Guide (on-line questionnaire) 

Appendix C: PHEV Design Games (on-line questionnaire) 

Appendix D: California and Northern California Survey Over-samples’ 

PHEV Designs 

Appendix E: PHEV Project Households’ Electricity Availability and 

Instantaneous Power Demand, Daily 

Appendix F: Three PHEV Project Households’ Narratives 
 143 

APPENDIX A: HOUSEHOLD FINAL INTERVIEW PROTOCOL

Questions about their experience with the PHEV 

[Questions and comments in brackets are rhetorical comments to guide the interviewer. 

The major numbered questions enumerate the topics for the interview. All lower-order 

questions are merely suggestions and prompts to be used if necessary to promote 

conversation.] 

Why did you want to participate in this research? What were your expectations? Hopes? 

Concerns? 

a. In what ways were your expectations met? [How do people “measure” 

this?] 

b. In what ways were they disappointed? 

c. Who drove the car? How did you decide? Did this change throughout the 

month? 

Tell me about driving the PHEV. What did you like? What didn’t you like? [Be sure to 

let people talk here. Their initial driving impressions may have to do with vehicle 

size, handling, cupholders, or other things. Only after they have told their story 

should you probe for any specifics of it being a PHEV.] 

d. Was your driving of the PHEV “normal” for you? Did you take any 

unusual trips? Did you not take trips you normally would have taken? 

How did your use of the PHEV change your travel for the month? 

e. Did you change your driving? In response to what? How? Why? [This 

question is about driving as opposed to travel. Did they drive more or less 

aggressively? What does that mean to them?] 

Could you tell when the vehicle was operating on electricity only? How? Was this 

important to you? Why, or why not? 
 144 

f. Tell me about the energy use instrumentation in the vehicle. Did you use 

it? How? Which screens did you use; to which information did you pay 

attention? 

Tell me about recharging the PHEV? Was it easy or difficult? A convenience or a hassle? 

g. How did your recharging behavior change over the month? Why? 

h. Can you imagine yourself doing recharging a vehicle over the long-term? 

Why? 

i. Would you change anything about your parking or access to 

electricity to improve recharging? 

i. Did you recharge away from your home? [No] Why not? [Yes. See 

prompts.] 

i. If you did, tell me about the places and times you recharged away 

from home. Were these casual or essential? What were you trying 

to accomplish? 

ii. How interested would you be in a PHEV if you did not have access 

to recharging at work? 

Did you notice changes (from your household’s own vehicles) in gasoline refueling, e.g., 

frequency, location, and cost? 

Did you track both electricity and gasoline use and cost? How? 

j. Was the V2Green website useful, interesting? 

i. How much did you use it? 

ii. Suggestions for changing the site? What would you like to see? 

Were you able to determine whether the PHEV “saved you energy/money, reduced 

emissions” anything? 
 145 

k. Would this be important to you, or would other things motivate you to 

drive a PHEV? 

l. What are these other things? How would you assess if you were getting 

enough of them to motivate you to drive a PHEV? 

Review questions from the on-line questionnaires 

Who answered the questionnaires? 

From Part 1, Question 3.11 [repeated below]: Why did they answer the way they did? 

You are offered the choice between two ways to reduce your household's energy use. 

Both simply require you to install them and then carry on with you usual life. Both 

are offered to you free. Option A would reduce electricity use in your home, reducing 

your monthly utility bill by $21. Option B would reduce gasoline use in your 

vehicles, reducing what you pay each month for gasoline by $21. 

Which would you choose? 

❏ It doesn't matter, I'll take either one 

❏ I'd rather spend $21 less per month on my electric bill (Option A) 

❏ I'd rather spend $21 less per month on gasoline (Option B) 

❏ I don't know 

From Part 2, Review results of design games: 

Did you read the guide? Was the game understandable? What did “all-electric” mean to 

you? 

Why did you create the PHEV designs you did? Did the game seem to get at what you 

thought would be important about PHEVs? What other feature or capability would 

you add? 

Would you say you would be more motivated to drive a PHEV that operated on 

electricity-only as much as possible or by a PHEV that had high fuel economy while 

operating on gasoline? 
 146 

m. What are your ideas about both these possibilities? What strikes you as 

interesting and valuable? 

n. How would you choose between them? 
 147 

APPENDIX B: PHEV BUYERS’ GUIDE (ON-LINE QUESTIONNAIRE) 

Your Plug-In Vehicle Guide 

Why read this guide?

Think of this as a 10 minute shopping guide. Part 3 of the ‘Household 

Vehicle Survey’ will allow you to design your own plug-in hybrid vehicle. 

You will determine how this technology might fit into your household’s 

lifestyle, if at all. This guide explains the design options you will be given in 

Part 3. 

This Guide Focuses on Plug in Hybrid Vehicles ONLY

A plug-in hybrid is a combination of an electric vehicle and a hybrid-electric 

vehicle. Recall the descriptions you were provided in Part 1 of the survey: 

Vehicle Type Description

A) Electric: An electric vehicle is fueled by electricity only. It is charged by 

plugging in to an electric outlet. The electricity is stored in the 

vehicle until it is used to power the vehicle. This technology is 

not currently produced by any major car companies, but a few 

smaller companies do. 

B) Hybrid-Electric: A hybrid-electric vehicle is fueled by gasoline only. It uses a 

hybrid-electric technology to use gasoline more efficiently. A 

hybrid-electric vehicle can not be plugged in to an electric outlet. 

This technology includes the Toyota Prius, which has become 

quite popular in the US. 

C) Plug-In Hybrid A plug-in hybrid combines these two technologies. It can be 

plugged in to an electric outlet to charge up with electricity, and 

it can be filled with gasoline. A plug-in hybrid can run on 

electricity only, gasoline only, or a combination of the two. 

No car company currently sells this technology, although several 

have plans. 

(*Note: This guide refers to ‘gasoline’ as your vehicle fuel, but this term includes whatever fuel your 

current vehicle uses, including diesel or ethanol)

Your Plug-In Hybrid Guide: 

Lesson 1: Refueling and Recharging ...........p.2-3

Lesson 2: Gasoline Mode (Driving Without Electricity) ..........p.4 

Lesson 3: Electric Mode (Driving With Electricity) ..........p.5-6

Lesson 4: Upgrading Your Plug-In Vehicle ..........p.7-8 
 148 

Lesson 1: Refueling and Recharging 

 

The plug-in hybrid is unique because it can be refueled with gasoline and 

recharged with electricity. Unlike a basic electric vehicle, the plug-in hybrid 

will still drive if it runs out of electricity (as long as you have gasoline left). 

Refueling and recharging your vehicle is simple: 

Refuel

At a gas station.

 

Recharge

Using an electrical outlet.

Gasoline: Refueling 

Refuel at any gasoline station. You have the same fuel tank you are used to, 

which holds the same amount of gas. If you want, you could use only

gasoline all the time without ever plugging in, just like your current vehicle. 

Electricity: Recharging 

Recharge your vehicle using any normal electrical outlet (110-volt) – just 

like you recharge your cell phone or laptop computer. These are the same 

types of outlets you use for a TV or toaster. An outlet might be at home, 

work, a store or a friend’s house, and would likely be outside or in a garage. 

Why plug-in when I could just use gasoline? 

Electricity is generally cheaper than gasoline...but it is difficult to say how 

much cheaper. Gasoline prices change often, and electricity prices vary by 

region, season, and other factors. In most regions today, driving with only

electricity would cost 60-80% less per mile than driving with only gasoline. 

This saving is like reducing your gas cost from $3.00/gallon to around $1.00. 

Also, driving with electricity usually causes less air pollution and 

greenhouse gas emissions than driving with gasoline. The size of these 

reductions depends on how your electricity is produced. 

AND/OR 
 149 

How long does it take to recharge?

Recharge time depends on the vehicle design you choose. An empty battery 

could take 1 to 8 hours to fully recharge. In Part 3 of the survey, you will be 

given the following four upgrade options when you design your own plug-in 

hybrid vehicles: 

1) 

8 Hours

2) 

4 Hours

3) 

2 Hours

4) 

1 Hour

Can I interrupt the recharging process?

Yes. For instance, if your vehicle requires 8 hours for a full charge, and you 

unplug it after 2 hours, you will get one quarter of a full charge. Similarly, 

you could plug it in for only 1 hour, or even 10 minutes. 

EXAMPLES: Recharge Upgrades 

Think of Paul and Sarah, two different drivers who each designed their own 

plug-in hybrid vehicles. Each driver completed a Plug-In Vehicle Diary to 

see what opportunities they have to recharge (access to electrical outlets). 

Paul’s family has only one place where they can recharge their vehicle: at 

their home garage where they park every night. Because Paul can recharge 

for 12 hours a day, he chose not to improve recharge time beyond 8 hours. 

Sarah lives in an apartment building, where there are no electric outlets near 

her parking spot. She drives around on business frequently during the day 

time, where she may occasionally be parked near an electrical outlet for 1-2 

hours at a time. Because she has only brief opportunities to recharge, Sarah 

chose to upgrade her plug-in vehicle recharge time to the quickest choice: 1 

hour. 
 150 

Lesson 2: Gasoline Mode (Driving Without Electricity)

All plug-in hybrid vehicles can drive without electricity. Once 

the battery runs out, the vehicle continues by using gasoline only. 

You could drive your plug-in vehicle without ever plugging in. 

‘Gasoline’ Mode: Efficiency Upgrade

A bonus of a plug-in hybrid vehicle is that once the electric charge runs out, 

the vehicle switches to ‘Gasoline’ mode and behaves just like a typical 

hybrid electric vehicle (like a Toyota Prius). This means that even if you 

don’t plug-in, a plug-in hybrid vehicle uses less gasoline than a regular 

vehicle. At a minimum, ‘Gasoline’ mode will allow you to drive an extra 10 

miles per gallon (+10 MPG) over a typical vehicle. If your current vehicle 

can travel 27 miles with a gallon of gasoline, the plug-in version could travel 

at least 37 miles. 

You will have 3 options to improve the efficiency of ‘Gasoline’ mode: 

1) Current Vehicle 

+10 MPG 

2) Current Vehicle 

 +20 MPG 

3) Current Vehicle 

+30 MPG 

Each improvement is relative to your current vehicle. If your current vehicle 

can drive 30 miles per gallon of fuel, you can upgrade ‘Gasoline’ mode 

efficiency to 40, 50 or 60 miles per gallon. 

EXAMPLES: Upgrading Gasoline Mode 

Again think of Paul and Sarah, who both vehicles that originally had a fuel 

efficiency of 27 miles per gallon (MPG). 

Paul’s family doesn’t drive in ‘Gasoline’ mode very often because they can 

recharge regularly at home. He chose the minimum upgrade of 37 MPG.

Sarah chose the maximum ‘Gasoline’ mode upgrade of 57 miles per 

gallon. She is interested in saving money, and she knows that on many days 

she can’t recharge at all. She wants to maximize her fuel savings even when 

she can’t use electricity. 
 151 

Lesson 3: Electric Mode (Driving With 

Electricity) 

If you recharge your plug-in vehicle, you can drive for some 

distance using electricity. Depending on your chosen design, electricity 

would either reduce gasoline use (Electric Assist) or replace gasoline use 

(All Electric) for this limited distance. 

Note: For all upgrades discussed in this guide, the vehicle’s performance 

does not change. For instance, improving gasoline efficiency or electricity 

use does not reduce acceleration, horsepower, top speed or towing ability. 

Electric Assist: Reducing Gasoline Use

When recharged, a vehicle that is ‘Electric Assist’ capable will use both 

electricity and gasoline at the same time. The electricity helps the gasoline 

engine, offsetting the gasoline required to drive. For instance, an average car 

can travel 27 miles with a gallon of gasoline (27 MPG). However, a charged 

plug-in hybrid can travel at a rate of at least 75 miles per gallon of gasoline 

(75 MPG), because the electricity is helping. Once the battery runs out, the 

vehicle returns to using gasoline only. You will not be stuck! 

There are 3 types of ‘Electric Assist’ plug-in hybrid vehicles. More 

advanced types use more electricity and less gasoline (represented by the 

changing size of the battery and gasoline icons in the diagrams below). 

Type #1: Electric Assist (75 MPG) 

Where electricity helps the gasoline engine, 

improving your gas mileage to 75 miles per 

gallon (MPG). Some gasoline is always required 

to drive. 

75 MPG

Electric Assist

Type #2: Electric Assist (100 MPG) 

Same as above, but improving your gas mileage 

to 100 miles per gallon (MPG). Some gasoline is 

always required to drive 

100 MPG

Electric Assist
 152 

Type #3: Electric Assist (125 MPG) 

Same as above, but improving your gas mileage 

to 125 miles per gallon (MPG). Some gasoline is 

always required to drive 

125 MPG

Electric Assist

All Electric: Temporarily Replacing Gasoline Use

A fourth type of electric design is ‘All Electric’ capable. This technology is more 

advanced than the ‘Electric Assist’ options because electricity can fully replace the 

use of gasoline for a limited distance. Once the battery has run out, the vehicle 

returns to using gasoline only. You will not be stuck! 

Type #4: All Electric 

Where electricity is temporarily used instead

of gasoline. As long as the vehicle is 

charged up, no gasoline is required to drive. All Electric

How long does the Electric Charge last? 

You can choose the distance your electric charge will last. This distance does not 

change if you choose Type #1, #2, #3 or #4. You can choose to have a full charge 

last for the first 10, 20 or 40 miles of travel. Beyond this distance, your vehicle 

returns to ‘Gasoline’ mode. If you choose 20 miles, your fully charged vehicle will 

drive in electric mode for the first 20 miles (‘Electric Assist’ or ‘All Electric’). 

When Fully Charged 

Drive in ‘Electric Assist’ or ‘All Electric’ Mode: 

1) For the First 

10 Miles

2) For the First 

20 Miles

3) For the First 

40 Miles

EXAMPLES: Upgrading Electric Mode and Electric Distance 

Again think of Paul and Sarah, two different plug-in hybrid owners. 

Paul likes the idea of driving an electric car in the city, so he chose a ‘Type #4: All 

Electric’ capable vehicle. He lives 6 miles from work (12 miles round trip), so he chose a 

vehicle with 10 miles of distance per charge. He can recharge each night, then commute 

to work, and most of the way home with only electricity. His vehicle switches to 

‘Gasoline’ mode for the last 2 miles of his commute. 

Sarah does not care if she uses gasoline or electricity; she just wants to save money. She 

chose the ‘Electric Assist’ capability, as she doesn’t think ‘All-Electric’ mode is worth 

the extra cost. She chose ‘Type #2: Electric Assist (100 MPG)’ so she can drive at a rate 

of 100 miles per gallon of gasoline (MPG). She also chose to upgrade to 40 miles of 

distance per charge, because she knows she cannot recharge regularly. 
 153 

Lesson 4: Upgrading Your Plug-In Vehicle

Minimum Upgrade Package 

In Part 3 of the survey, you will use an interactive diagram to design your ideal plug-in 

hybrid vehicle (given different constraints). The diagram below shows the baseline plugin upgrade package you will be shown, with the minimum values shown for each option: 

This plug-in hybrid vehicle requires 8 hours to fully recharge. When charged, it can drive 

with ‘Type #1: Electric Assist (75 MPG)’ for the first 10 miles. After 10 miles, the 

vehicle switches to gasoline mode, which can travel 10 more miles per gallon (MPG) of 

gasoline than your current vehicle. 

Your Plug-In Hybrid 

Vehicle 

Upgrades 

Recharge Time: 

8 Hours

Time to Fully Recharge: 

8 Hours 

 4 Hours 

 2 Hours 

 1 Hour 

Electric Capability:

Type #1: Electric Assist (75 MPG) 

 Type #2: Electric Assist (100 MPG) 

 Type #3: Electric Assist (125 MPG) 

 Type #4: All Electric 

Electric Mode: 

75 MPG

Electric Assist

For the First 

10 Miles 

Distance With Electric Capability:

First 10 miles 

 First 20 miles 

 First 40 miles 

Gasoline Mode:

Your Vehicle +10 MPG 

Gasoline Use:

+10 Miles Per Gallon 

 +20 Miles Per Gallon 

 +30 Miles Per Gallon 
 154 

EXAMPLES: 

Here is a summary of the plug-in upgrades Paul and Sarah chose: 

Paul’s family chose a plug-in vehicle that takes 8 hours to fully recharge. When 

fully charged, the vehicle can drive without any gasoline (Type #4: All Electric) 

for the first 10 miles. After 10 miles (unless recharged), the vehicle runs out of 

electricity and uses gasoline only (37 MPG), but still saves fuel compared to a 

regular vehicle (+10 miles per gallon). 

Sarah chose a plug-in vehicle that takes only 1 hour to recharge. The fully 

charged vehicle can drive with Electric Assist (Type #2) for 40 miles, using 

electricity to boost fuel economy up to 100 miles per gallon. After 40 miles, the 

vehicle switches to gasoline only, where her vehicle can travel an extra 30 miles 

per gallon of gasoline (57 MPG) compared to a typical vehicle. 

Paul’s Upgrades Sarah’s Upgrades 

Recharge Time: 

8 Hours

Recharge: 

8 Hours 

 4 Hours 

 2 Hours 

 1 Hour 

Recharge Time: 

1 Hour

Recharge: 

 8 Hours 

 4 Hours 

 2 Hours 

1 Hour 

Electric:

 Type #1 

 Type #2 

 Type #3 

Type #4 

Electric:

 Type #1 

Type #2 

 Type #3 

 Type #4 

Electric Mode: 

All Electric

For the First 

10 Miles 

Distance:

10 miles 

 20 miles 

 40 miles 

Electric Mode: 

100 MPG

Electric Assist

For the First 

40 Miles 

Distance:

 10 miles 

 20 miles 

40 miles 

Gasoline Mode:

37 MPG 

Gasoline:

+10 MPG 

 +20 MPG 

 +30 MPG 

Gasoline Mode:

57 MPG 

Gasoline:

 +10 MPG 

 +20 MPG 

+30 MPG 

Now think about your household. Which upgrades are 

important? Please consult with your family to prioritize these 

upgrades. 
 155 

APPENDIX C: PHEV DESIGN GAMES (ON-LINE QUESTIONNAIRE) 

Section 3: Designing Your Plug-In Vehicle 

Now, Imagine that... you have a just won a contest to upgrade your MINI COOPER

into a plug-in hybrid vehicle, allowing you to use electricity to drive, using less gasoline. 

This upgrade promises that everything else about your vehicle will stay the same 

(appearance, performance, safety, warranty, etc.). 

Remember, A Plug-in Hybrid is... a vehicle that can be powered by either: electricity 

(from an electrical outlet), gasoline (like a typical vehicle), or a combination of both, as 

shown below: 

 

Electricity Only

OR

Gasoline Only

OR

Both Electricity and Gasoline

You Have Choices... because your 'Plug-in Prize' allows you to choose what kind of 

battery upgrade you receive. But first... 

First We Need to Know... 

What is the average fuel economy of your MINI COOPER in miles per gallon (MPG)? 

Choose a value that is the average of city/highway driving.

(Remember, a higher MPG means you are required less fuel to drive a given distance.) 

21 MPG - About average for a new truck 

27 MPG - About average for a new car 

28 MPG - About average for a basic MINI COOPER

Other - Please Specify: MPG 

Next
 156 

Now you have the opportunity to upgrade your vehicle. You can upgrade your plug-in 

vehicle in four different ways, as described in Your Plug-In Vehicle Guide. Please 

consult this document for explanations if you need help. 

Each upgrade requires a certain number of points. We want to know what upgrades 

you consider to be most important. You will be shown 5 scenarios. Each scenario will 

give you a different number of points to make upgrades. Each scenario is 

independent, so you can choose different upgrades each time. 

Scenario #1: If you have 1 point to make an upgrade, how would you use 

it? 

Please be realistic. Consider how your household uses this vehicle, and where you have 

access to electrical outlets, if at all (from your plug-in diary). 

Make your selection(s) in the Upgrade column to use your points, then click 'This is My 

Choice' when you are finished.

Your choice is visually represented in the left column.
 157 

Description of Your Choice:

The above vehicle takes 8 hours to recharge. When fully recharged, it can be driven for 

the first 10 miles in Type #1: Electric Assist (75 MPG) mode. After this distance, it can 

only be driven in gasoline mode until recharged, getting 33 Miles Per Gallon. 

This is My Choice
 158 

Scenario #2: If you have 2 point to make an upgrade, how would you use 

it? 

Description of Your Choice:

The above vehicle takes 8 Hours to recharge. When fully recharged, it can be driven for 

the First 10 miles in Type #1: Electric Assist (75 MPG) mode. After this distance, it 

can only be driven in gasoline mode until recharged, getting 58 Miles Per Gallon

This is My Choice
 159 

Scenario #3: If you have 4 point to make an upgrade, how would you use 

it? 

 

Description of Your Choice:

The above vehicle takes 8 Hours to recharge. When fully recharged, it can be driven for 

the First 10 miles in Type #4: All Electric mode. After this distance, it can only be 

driven in gasoline mode until recharged, getting 38 Miles Per Gallon

This is My Choice
 160 

Scenario #4: If you have 6 point to make an upgrade, how would you use 

it? 

Description of Your Choice:

The above vehicle takes 8 Hours to recharge. When fully recharged, it can be driven for 

the First 40 miles in Type #4: All Electric mode. After this distance, it can only be 

driven in gasoline mode until recharged, getting 38 Miles Per Gallon

This is My Choice
 161 

Scenario #5: If you have 8 point to make an upgrade, how would you use 

it? 

Description of Your Choice:

The above vehicle takes 4 Hours to recharge. When fully recharged, it can be driven for 

the First 40 miles in Type #4: All Electric mode. After this distance, it can only be 

driven in gasoline mode until recharged, getting 48 Miles Per Gallon

This is My Choice
 162 

Section 4: Next Vehicle Purchase 

This section will present a game to simulate your household's next new vehicle purchase. 

First, we ask several questions about your household's intentions. 

1) Which of the following statements best summarizes your household's plans to 

purchase your next new vehicle? 

My household has...

...already picked out our next vehicle 

...discussed a few different vehicles models, but has not yet decided on one 

...a rough idea of what vehicle to buy next, but has not yet looked around 

...not yet thought about our next vehicle 

2) How soon do you believe your household will buy or lease its next new vehicle? 

Within the next 6 months 

Between 6 months and 1 years from now 

Between 1 and 2 years from now 

Between 2 and 5 years from now 

More than 5 years from now 

We have no idea. 

3) Which of the following best describes your next vehicle purchase? 

The next vehicle my household purchases will...

...replace the MINI COOPER

...replace another vehicle 

...not replace any vehicle, but will be an addition 

We have no idea. 
 163 

4) When your household buys or leases its next new vehicle, which of the following 

descriptions best describes the vehicle type you will likely choose? 

Compact car 

Midsize Car 

Large Car 

Small SUV 

Midsize SUV 

Large SUV 

Minivan 

Cargo van 

Small pickup truck 

Large pickup truck 

We have no idea 

Next

5) For this last section, we will refer to the type of vehicle your household will likely buy 

or lease next. Please select a make and model that best describes your next vehicle. If you 

are unsure, you can simply select your current vehicle (MINI COOPER). 

I choose MINI COOPER

I would like to select another vehicle. Please specify Make and Model: 

 

 Example: Make = Honda 

Model = Accord

Make: 

Make

Model: 

Model

Click here if your vehicle isn't listed above. 

Next
 164 

From here on, we assume that your household's next vehicle purchase will be a new 

FORD MUSTANG. 

6) About how much do you think your household will spend to buy this FORD 

MUSTANG? 

$27000 - About the base cost of a FORD MUSTANG

Another value - Please Specify: Thousand 

7) What do you think will be the approximate fuel economy (Miles Per Gallon - MPG) of 

this FORD MUSTANG you will buy? 

Choose a value that is the average of city/highway driving. 

(Remember, a higher MPG means you required less fuel to drive a given distance.) 

21 MPG - About average for a new truck 

27 MPG - About average for a new car 

28 MPG - About average for your basic MINI COOPER

25 MPG - About average for brand new 2007 basic FORD MUSTANG

Another value - Please Specify: MPG 

Next

You will be shown 3 scenarios. Each scenario you will show you different prices for the 

plug-in hybrid options and upgrades. Each scenario is independent, so you can choose 

different vehicles or upgrades each time. 

You can customize the specific features of the plug-in version, just as you did in the 

previous exercise. Again, refer to Your Plug-In Vehicle Guide for help in choosing 

upgrades, particularly the summary on pages 7 to 8. 

Given the two options below, which would your household likely purchase? 

Other than the price, the plug-in feature, and fuel consumption, every other characteristic 

of the two vehicles are identical. In other words, the plug-in version of the FORD 

MUSTANG has the same body, performance, interior size, etc. as the regular FORD 

MUSTANG. 

Please be realistic, and consider your expected household budget constraints 
 165 

Price Scenario #1 (Low Cost Scenario – Order Randomized) 

This is My Choice
 166 

Price Scenario #2 (Medium Cost Scenario – Order Randomized) 

This is My Choice
 167 

Price Scenario #3 (High Cost Scenario – Order Randomized)

This is My Choice
 168 

APPENDIX D: CALIFORNIA AND NORTHERN CALIFORNIA SURVEY OVERSAMPLES’ PHEV DESIGNS

Figure D1: Upgrades selected in PHEV design games by California plausible early 

market only, n=286 

0%

20%

40%

60%

80%

100%

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Base Model

Recharge

CD Type

CD Range

CS MPG

Base Model

% Choosing Upgrade

Base Model

3rd Level Upgrade

2nd Level Upgrade

1st Level Upgrade

Game 1: Development Priority (Points) Game 2: Purchase Design ($)

Round 1

(1pt)

Round 2

(2pt)

Round 3

(4pt)

Round 4

(6pt)

Round 5

(8pt)

“High”

Price

“Low”

Price

0%

20%

40%

60%

80%

100%

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Base Model

Recharge

CD Type

CD Range

CS MPG

Base Model

% Choosing Upgrade

Base Model

3rd Level Upgrade

2nd Level Upgrade

1st Level Upgrade

Game 1: Development Priority (Points) Game 2: Purchase Design ($)

Round 1

(1pt)

Round 2

(2pt)

Round 3

(4pt)

Round 4

(6pt)

Round 5

(8pt)

“High”

Price

“Low”

Price

0%

20%

40%

60%

80%

100%

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Base Model

Recharge

CD Type

CD Range

CS MPG

Base Model

% Choosing Upgrade

Base Model

3rd Level Upgrade

2nd Level Upgrade

1st Level Upgrade

Game 1: Development Priority (Points) Game 2: Purchase Design ($)

Round 1

(1pt)

Round 2

(2pt)

Round 3

(4pt)

Round 4

(6pt)

Round 5

(8pt)

“High”

Price

“Low”

Price
 169 

Figure D2: Upgrades selected in PHEV design games by northern California 

plausible early market only, n=63) 

0%

20%

40%

60%

80%

100%

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Base Model

Recharge

CD Type

CD Range

CS MPG

Base Model

% Choosing Upgrad

e

Base Model

3rd Level Upgrade

2nd Level Upgrade

1st Level Upgrade

Game 1: Development Priority (Points) Game 2: Purchase Design ($)

Round 1

(1pt)

Round 2

(2pt)

Round 3

(4pt)

Round 4

(6pt)

Round 5

(8pt)

“High”

Price

“Low”

Price

0%

20%

40%

60%

80%

100%

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Recharge

CD Type

CD Range

CS MPG

Base Model

Recharge

CD Type

CD Range

CS MPG

Base Model

% Choosing Upgrad

e

Base Model

3rd Level Upgrade

2nd Level Upgrade

1st Level Upgrade

Game 1: Development Priority (Points) Game 2: Purchase Design ($)

Round 1

(1pt)

Round 2

(2pt)

Round 3

(4pt)

Round 4

(6pt)

Round 5

(8pt)

“High”

Price

“Low”

Price
 170 

APPENDIX E: PHEV PROJECT HOUSEHOLDS’ ELECTRICITY AVAILABILITY 

AND INSTANTANEOUS POWER DEMAND, DAILY

Electricity Availability, Percent of PHEVs Plugged-in throughout each Day 

of the Week 
 171 
 172 
 173 
 174 

Instantaneous Power Demand Summed for all Households, Watts 
 175 
 176 
 177 
 178 

APPENDIX F: THREE PHEV PROJECT HOUSEHOLDS’ NARRATIVES

1. Rick and Samantha Lake 

Summary Paraphrases: 

Rick: “A PHEV has to payback to be worth it, but I’ll kick in an extra 10% premium to 

do my part—to reduce environmental damage for the next generation. I am most excited 

about the idea of a PHEV that lets me commute without turning on the engine at all—as 

little as 10 miles of range would do because I would find a way to plug in at work.” 

Samantha: “The increased fuel economy sounds good—to save money and contribute to 

the solution of global resource problems. But we are not willing to compromise much on 

functionality—the vehicle would have to fit into our family’s lifestyle, such as storing 

groceries and allowing long road trips.” 

Young son: “Will this car save the earth?” 

The Beginning 

Rick and Samantha Lake are married and in their early 40’s. They live in a large house in 

a gated community and the living room and kitchen are filled with toys for their two 

boys, aged four and eight (who played video games in the same room as us during all 

three interviews). Rick works in financial services, while Samantha is currently devoted 

to looking after the kids and running the household—their reported household income is 

over $150,000. They own two cars: a 2002 Honda Accord—which they temporarily 

replaced with the PHEV—and a 2004 Honda Odyssey. Rick primarily uses the Accord 

for work-related trips, while Samantha uses the Odyssey for running errands with the 

kids. It is also for family road trips. 

Prior to their PHEV trial, Rick and Samantha were fairly familiar with electric-drive 

vehicles. They knew neighbors that drove neighborhood EVs, such as the GEM, which 

Rick described as: “like a big golf cart...novel...but it doesn’t go very fast, like 35 or 45 

miles per hour...they must live near by [their destination],” but overall “not very 
 179 

practical.” Samantha perceived that increasingly more neighbors with longer commutes 

were buying Priuses as commute cars—hybrids were “fairly popular in the gate.” Rick 

had been in a Honda Civic Hybrid before; he laughed about an incident when a coworker drove him in a company-owned HEV, and the co-worker thought the vehicle had 

“died” when the engine turned off at a stop light and tried to “start cranking it.” Although 

they were initially unclear about the functions and abilities of PHEV technology, Rick 

had seen a news clip highlighting the UC Davis PHEV Center on the local cable channel, 

where Center Director Tom Turrentine showed off the battery of a PHEV conversion. 

Rick recalled the statement that a driver could get 100 mpg for the first 40 miles—so he 

was “shooting for 100 mpg” during the trial. 

Rick recalled being excited when he received the invitation letter for the PHEV study. He 

noted that it coincided with a project he was engaged in at work—a training program on 

“going green,” where he was focusing on green buildings, and he looked forward to 

sharing insights with his group (during the trial, he repeatedly asked for PHEV 

pamphlets, and tried to arrange a photo opportunity with the PHEV Center’s vehicle that 

prominently displays that it is a PHEV). They anticipated Rick would do most of the 

driving because they were replacing his car—which he stored at his mother’s house for 

the duration of their trial. The Lakes did not ask very many technical questions at the 

drop-off meeting, but they were curious about how often they should plug the vehicle in. 

All four family members took part in the test drive, during which the eight-year old boy 

asked: “will this car save the earth?” (Samantha noted that he was in an environmental 

club or program at his school.) 

The Overall Driving Experience 

Overall, the Lakes enjoyed driving the PHEV. Rick was the main driver, using it for his 

19-mile roundtrip commute and other work-related trips. Rick stated that it “took a day or 

two to get used to,” but after that it proved to be a “nice, smooth little car” that was “very 

practical” and “handled pretty well.” He said that “for a day-to-day commute, its great” 

and it fit into their lifestyle “fairly seamlessly.” He “was expecting high mileage, and it 

delivered.” Rick’s assessment of the PHEV was at least partially related to his 
 180 

perceptions of pure EVs: “for me it was the combination of having the gas and electric 

assist—it made it easier to integrate into our life than pure electric, because it had that gas 

component you never really worried. If it was just electric...you’d have to plan out your 

route more, make sure there is a cord somewhere to charge it...but because it had that gas 

component it was fairly seamless, aside from plugging-in at night.” Rick was critical of 

certain specific features: he found the provided 50 foot electrical cord to be awkwardly 

long (he just kept it in his garage), and immediately removed the spare tire to maximize 

their cargo space. He was also frustrated that the engine would come on even during short 

trips: when “its burning gas, and I don’t need it...just half a mile...why doesn’t it just run 

on electricity?” 

Samantha drove at most once per week, running errands such as taking the kids to 

school—no more than 5 or 6 days during the trial. Like Rick, she took some time to get 

used to the PHEV; she attributed initial awkwardness to the general differences between 

Toyotas and Hondas (“all Hondas are the same”), as well as getting used to the keyless 

system. Overall, she also liked her experience with the vehicle, noting that it was 

“peppy.” She also compared it to a pure EV, noting that she liked “knowing that I have a 

full tank there...I know I’m not going to run out...(with an EV) I’d be looking to see how 

far I can go...and if can I plug in once I’m there...with this (PHEV) we think we can go 

pretty much anywhere and be okay.” She stated that the kids were also happy with it—

“maybe the novelty of a new thing”—and would often say “let’s take the electric car 

today” instead of the minivan. Samantha noted that the PHEV would not likely work for 

the longer distance road trips they normally took every couple of months (but not during 

the trial), such as trips to LA, during which they would “pile in a week or 10 days worth 

of stuff,” summarizing that “a road trip is easier with a bigger car.” 

The Lakes agreed that, in general, their driving behavior during the trial was fairly 

representative of their typical patterns. After several minutes of discussion between them, 

they concluded that the first two weeks were more typical of the distance and types of 

trips they would make, as well as the split between Rick and Samantha as driver, while 

the latter two weeks were more representative of the fuel economy they would likely 
 181 

achieve in the long run (where Rick paid less attention to the energy instrumentation, 

etc.—more on this below). 

Recharging 

Rick recharged the PHEV at home very regularly, plugging it in every night and 

unplugging it every morning, and sometimes plugging it in again during the afternoon 

between trips. Samantha stated that recharging took a little getting used to, where on the 

first day she noticed that Rick almost drove away without unplugging the cord (“...after 

that we always remembered”). In the interest of further simplifying the recharge process, 

they both envisioned a vehicle with a retractable cord. For home recharging, they had a 

general idea that electricity would be cheaper at night, but were not sure when or how 

much, and did not plan around this. Rick simply recalled reading about rate differences 

on a website, and Samantha thought the difference might start at 8 or 9pm (she recalled a 

suggestion that laundry loads would be cheaper after this time). 

The Lakes did not recharge at another location during the trial. Rick described why his 

workplace wouldn’t work: “I started looking for plugs everywhere...where [the electrical 

outlet] was situated it would be a hazard...between two banks of elevators...that’s not 

going to work...to make it more viable to plug in the employers would have to get in on 

the act...to have outlets.” He felt he might get sued if someone tripped over it, so the risk 

was not worth it. Rick did notice “EV-only” parking spots at some locations, such as the 

library and mall, but he wasn’t sure if he was allowed to use it. Samantha added that it 

was just easier to plug-in at home anyway. 

Energy Use and Instrumentation 

Rick described a shift in his use of the PHEV over the course of the trial: “it was a 

novelty at the beginning...I was babying it a lot...now I just drive it normal.” At first he 

liked to monitor how he as “doing” by watching his mpg as well as the Energy Monitor 

diagram to see if the battery was being used. He would experiment with different 

behaviors: “I’d gas it and watch it...put my foot of the throttle and watch it...I’m 

probably a dangerous driver...out of curiosity to see how my actions affected things...air 
 182 

conditioner, not air conditioner.” He said it was this “curiosity” that led him to watch the 

instruments “more than [he] should.” Rick was also motivated by his goal of achieving 

100 mpg or higher: “...but I didn’t quite get there...for a trip I never got close...oh no, I 

take that back, I did hit it once. If I look at the travel log (V2Green website) there are 

actually a few days where I hit 100...I was coasting a lot.” (Indeed, according to 

V2Green, about two weeks into the trial he did achieve ~108 mpg during two 9.8 mile 

trips from work to home. Otherwise, his to-work mileage ranged from 68 to 82 mpg—

generally decreasing over the trial—and his from-work mileage was typically higher for a 

given day by 2 to 15 mpg. Figure 1 illustrates these patterns.) 

Figure 1: Rick Lake’s ~10 mile (one-way) commute (gasoline-only) mpg 

over their PHEV trial 

0

20

40

60

80

100

120

M T Th W Th F M T

Day of week

Trip MPG

To work

From work

In contrast to Rick’s initial focus on the energy-use instrumentation, Samantha stated: 

“I’m the opposite: oblivious...just driving...I pay attention to the road mainly.” She 

reasons that because she is driving fast she has “got to pay attention,” and thinks that 

Rick looks at the screen too much. She figures that, after all, the PHEV “was gonna do 
 183 

what it was gonna do.” As Rick talked about trying to achieve 99.9 mpg on the highway, 

Samantha added, “People are honking at you.” 

Once the Lakes were given access to V2Green, Rick made regular use of the website, and 

seemed to integrate the provided information into his assessment of the vehicle. At the 

midterm interview, prior to access to V2Green, he was highly uncertain about his overall 

fuel economy—he guessed somewhere between 50 and 100 mpg (“99.9 half the time, and 

50 otherwise”). However, he noted he had not yet had the chance to make a more precise 

estimate because he hadn’t refueled the PHEV, and he normally calculated fuel economy 

when he fuels up his cars (“just out of general interest,” according to the survey). After 

getting V2Green access, he would regularly scan the website at work (the kids were too 

distracting at home). He says he looked at everything, but found the mpg most useful—

the rest was “gee-whiz” information, such as the duration of recharge episodes, distances 

driven, and kWh used. While he claims not to have used the website to change his driving 

habits, he feels he would use the website at least weekly in the long-term. 

Because of his continued monitoring, Rick was more knowledgeable about his fuel 

economy for the final interview. He knew his overall mileage was around 60 for the 

month [our calculation is 62.8 mpg], and noticed that his fuel economy dropped 

dramatically during the latter half of the month, which he observed was largely due to 

longer trips out of town. During one longer trip he recalled that he achieved about 75 

mpg on his way to the meeting, but only 58 or 59 on way back. He estimated he was 

averaging around 75 mpg for the first half of the month, but his overall average dropped 

due to these longer trips [our calculation is 70.4 mpg for the first two weeks, and 58.6 for 

the latter two]. He also admits that in the latter half he had been driving “more normally, 

more aggressively...instead of coasting I was accelerating to make freeway speed.” Rick 

also used the information to (playfully) compare his fuel economy with Samantha’s: 

Rick: “when I drive its about 75, when you (Samantha) drives its about 

50...I looked on the internet (laughs)” 

Samantha: “...what does that mean—highway vs. city?” 
 184 

Rick: “...could be...or more aggressive accelerations...I coast a lot” 

Samantha: “...I’m in a rush to get somewhere...” 

Rick: “...right, nobody passes mommy (laughs)...” 

Over the month, Rick estimates they spent about $26 on gasoline for the PHEVconversion. Although they acknowledged driving the PHEV a little more than they would 

drive the Accord (they took the PHEV on some weekend trips that the minivan would 

normally be used for), Rick estimated they saved about 30% on fuel costs over their 

Accord. He considered electricity in this estimate, but admitted he couldn’t precisely 

estimate the electricity costs until he saw their next bill. 

Talking to Others 

Samantha noted that a couple of neighbors asked about the PHEV during the trial. She 

didn’t recall any in-depth questions, just a few questions about “what’s that plug in the 

back?” and little bit of follow up discussion. Rick added that, at home, they didn’t park 

the PHEV outside, so there was little opportunity for others to see it. The few neighbors 

he talked to were interested in what fuel mileage the vehicle could get, how they could 

get in the study, if they could buy one, and if Rick would buy one after the trial. Rick’s 

coworkers were also curious, particularly those involved in the “going green” training 

program. Some had already looked into PHEV conversions and were aware of the 

$12,000 price tag for A123System’s retrofit. Rick told neighbors and coworkers that he 

would not be willing to pay so much for such a retrofit, though he might pay a smaller, 

“reasonable” premium—$12,000 would require too long a payback period. 

One Motive for Purchase: Payback 

At the midterm interview, Rick pointed out that he might be a “bad person” for this study 

because he is the type who will “always try to do the cost-benefit analysis” [likely rooted 

in his educational background and present employment]. He says: “I try to capitalize 

everything—I would take the present value of my costs and all that, and ooh, right now it 

doesn’t pencil out...for the (Lexus Hybrid) you’re going to pay an extra 10 grand—to me 
 185 

it doesn’t pencil out.” He further illustrates the importance of this financial motive with a 

story of his brother-in-law’s (who is also a coworker) purchase of a low-energy water 

heater: 

“His water heater just went out and they got a tankless water heater (for 

$3000)...and I said it will never pay back... you can get one for $700. Did you 

discount the cash flows...the difference? And he says (he) did ‘...on a pure 

economic basis it is not worth it...but we’re doing our part....’ His thought is 

you lower your carbon footprint or something like that...I said ‘okay, as long as 

we’re clear.’ Once this (PHEV) study is done I’ll do the same...I’ll run the 

numbers to see the payback period for the difference in savings. I like the fact 

that it’s green...I haven’t seen An Inconvenient Truth, but I’d like to...but I think 

that for a lot of consumers it will be dollars and cents...but then you’ll have 

some pure guys that are saying its better for the environment, I’ll pay the 

premium to do my part.” 

During this midterm interview, Rick described his tendency to favor the financial 

perspective, but neither Rick nor Samantha appeared to clearly support or reject the prosocietal motive of “doing your part”—Rick merely noted it as a possible perspective. 

Interestingly, Rick also stated that high gas prices were not a serious problem for their 

household: “it was more of an irritant...it didn’t really affect our life at all.” [This 

interesting contrast—where the idea of payback is very important but money itself is less 

so—indicates that for Rick, payback is tied into something else. Maybe he feels some 

dedication to making smart decisions, and not getting duped into paying too much for 

environmental purchases?] 

Another Motive: “Doing our Part” 

In the final interview, Rick and Samantha further elaborated on the pro-societal 

perspective hinted at during the midterm—this time describing how such non-financial 

motives were also important to them. When asked what specifically he liked about the 

PHEV, Rick included the potential to reduce CO2 emissions through reduced gas use, at 

least “in theory.” He further states: “I don’t know whether or not it really reduces 
 186 

pollution...but its nice to think it does...nice to have the perception that you are doing 

something to help out.” Rick’s uncertainty seems to stem from both the nature of 

electricity generation and battery production. He figures that “in theory” using electricity 

“reduces the dependency on fossil fuels, petroleum products...here we do hydro, and 

back east they do what, coal? ...And nuclear ...here, maybe some wind farms and solar 

farms ...so you reduce your dependency on fuel.” After “poking around on the internet,” 

Rick also thinks it might be “really expensive to build the batteries...lithium-ion 

batteries...so I don’t know economically how much it makes sense...but I guess it would 

definitely reduce your dependency on gas...but I don’t know what the reality is.” Despite 

this uncertainty, Rick highlights the importance of “doing our part” in regards to “not 

using more (resources) than you need to” and not adding “more pollutants out there than 

you have to.” 

Samantha described how, when gas prices recently went up, they saw more shows talking 

about natural resources: “how much we have and why, and the other developing countries 

like India and China who are now playing a bigger role in wanting the resources... now 

the US is competing more...there is only a finite amount...I think we need to figure out 

ways to make sure that globally everyone gets what they need...we can’t always say that 

whatever we need we should be able to get...so I think we can all work at that, whatever 

it is...we’ve got to pass on the world to the next generation.” At this point Rick related 

this issue to his children’s future: “we’ll probably be okay in our generation, but their 

generation (points at kids) is going to suffer unless we do something...use renewable 

resources...like solar, or hydrogen I guess.” 

Rick and Samantha agree that the world is generally moving in a better direction. Rick 

thinks it is good that there is more public education about global warming, and Samantha 

added that she sees more people willing to ride the bus. Rick described how he learned to 

take the bus to work about once per week (at first it took 50 minutes one way—“that’s 

not going to happen”—but he found a faster express route). He also explained how some 

people just don’t seem to get the “doing your part” idea, such as a neighbor that saw him 

walking home from the bus on day: 
 187 

“‘Oh, [Rick], what are you doing?’ I said, ‘Coming home from work.’ She said, 

‘You taking the bus?...I’d never do that, why are you taking the bus?’ I replied, 

‘I felt like doing my part, I try to take it once or twice per week.’ She says: ‘Oh, 

I’d never do that...but kudos to you!’ And turned around and walked away!” 

Future Car Purchase 

The Lakes were very interested in the idea of purchasing a PHEV, but they had specific 

needs they wanted it to meet. Rick noted that while the PHEV-conversion they had been 

driving was a good “day to day” commute vehicle, they would want to keep a second 

vehicle for the family—something that seated 7 or 8. He also wants the purchase to make 

economic sense: “I would do a little cost-benefit analysis...you can kick in a little 

premium, maybe a 10% premium just to go green or do your part for the environment to 

be a good citizen...but beyond that I don’t know, I’d have to wait for (the price) to come 

down.” Rick was clear he would not want to pay the 50% premium currently required for 

the A123Systems conversions. Samantha agreed that cost would play a part in their 

decision, but she felt that while Rick “wants to crunch it out,” she is “more the gut-feel 

type.” She might be willing to pay 24 or 28 thousand for PHEV Prius, but wants to 

consider other things like “reliability, size” and for the environment she “doesn’t know 

where [her] cut off is.” She says she certainly wouldn’t want anything smaller than the 

Prius. [I think Samantha noted that she also has a quantitative background like Rick, but 

she was just not as likely to use it at home.] 

For the design games, Rick seemed most excited about the idea of all-electric operation 

for his hypothetical Lexus RX 330 (see results in Table 1). In Game 1 (Priority 

Development), he chose the all-electric upgrade as soon as it became available in Round 

3—which means at the expense of any other upgrades [note: not many respondents 

choose this]. When he originally completed Game 2 (Purchase Intention) online (without 

much input from Samantha), he only chose the PHEV upgrade in the lowest price 

scenario, in which he selected 10 miles of all-electric range, and maximized the CS fuel 

economy [We don’t have direct corroboration from Rick, but we suspect that he was not 

as excited about the PHEV upgrades that were too expensive to justify his vision of an 
 188 

all-electric commute]. When asked, he explained he only needed 10 miles of range to get 

to work, and once there “tripping or not, I’d find a plug...if it meant that I could make it 

there and come back without having to gas up, I’d hit up somebody to build me a 

plug...(or) I would show up so early to park next to that plug, to save 5 bucks (laughs).” 

[Note that in the midterm interview, workplace recharging sounded infeasible—by the 

final interview he was fired up about making it happen]. This enthusiasm for all-electric 

driving links to his assessment of the PHEV trial: “I wish it had a pure electric mode, I 

wish I could just flick a switch and say: run on electricity as long as you can...because I 

think I could make it to work and back without having to use the gas...but with this one 

when you fire it up, the engine runs.” He also heard that driving with electricity was 

equivalent to $0.75/gallon gas, which would save money, plus he wouldn’t have to stop 

at a gas station—“who knows if some goofy guy is going to jump you.” 

Table 1: The Lake’s PHEV design game results (moderate and high price 

scenarios include adjustments from consultation with Samantha) 

 Low Price 

(Shown first) 

Moderate Price 

(Shown second) 

High Price 

(Shown last) 

 

Lexus 

RX 330 

PHEV 

Lexus RX 

330 

Lexus RX 

330 

PHEV 

Lexus RX 

330 

Lexus RX 

330 

PHEV 

Lexus RX 

330 

Recharge hours 8 8 8 

CD mpg AE (+$2k) 75 75 

CD miles 10 10 10 

CS mpg 56 (+$500) 56 (+$1k) 56 (+$2k) 

Regular mpg 26 26 26 

Base Price $22,000 $24,000 $22,000 $25,000 $22,000 $26,000 

Upgrades $2,500 $1,000 $2,000 

Total Price $22,000 $26,500 $22,000 $26,000 $22,000 $28,000 

Bought Yes Yes Yes 
 189 

Samantha was unsure about her husband’s initial selections. (Rick was responsive to her 

concerns: “I don’t buy anything unless momma approves (laughs).”) At first, she didn’t 

understand his focus on 10 miles of all-electric range [I don’t think she saw his vision of 

an all-electric commute, and she was also confused about whether all-electric meant a 

pure EV]. Samantha also disagreed with Rick’s selections in the higher price games—she 

thought that the PHEV with CS upgrade could be worth the extra money. They discussed 

these options for several minutes—at one point Rick decided he needed to do a payback 

calculation and got up to get his business calculator. He sat down, pressed buttons for less 

than a minute, and then concluded, “Yeah I would by it” (agreeing with Samantha’s 

selections). When asked to explain his calculation, he said: “I took my average miles per 

month, and the difference in gas, at two bucks per gallon, then I discounted it at a safe 

rate (5%) for 10 years...took a present value.” He also figured that gasoline prices would 

likely go up again, so the net present value would be even more compelling. In summary, 

the Lakes both felt that faster recharge times were not necessary—they would mainly 

recharge at home. They would be willing to pay extra for PHEV upgrades with 

maximized CS fuel economy in all price scenarios. Only in the low-price scenario would 

they also upgrade to all-electric range for the 10 miles of CD range—thus achieving 

Rick’s initial vision of an all-electric commute. 

Rick and Samantha Lake were both interested and motivated to explore the PHEV 

technology for economic and environmental reasons. They were willing to pay a 

premium to do their part for the environment, while at the same time were concerned 

with fuel savings and conversion costs. 

2. Nancy 

Summary Paraphrase 

“I don’t plan on just sitting around a lot. I want to be able to drive when I can, and I want 

to be able to afford the gas. I never would have picked that car, but, after driving it for a 

month, it just feels right. I really would like to buy one with a plug if I could afford it, 

because I really feel like I am getting the most for my money when I use the electricity. 
 190 

But I really don’t know what the regular Prius is like. I might be OK with one of those ... 

does it feel the same?” 

Who is Nancy? 

Nancy is a single retired grandmother who lives in an older, modestly sized, detached 

home. She spends a considerable amount of time caring for her granddaughter, and she is 

the primary caregiver for her 8-year old grandson. As a caregiver with a single income, 

Nancy admittedly watches her money closely, and is always looking to get the most for 

it. While participating, she substituted the PHEV completely for her only vehicle, a 1991 

Toyota Camry with 253,000 miles. 

Nancy was drawn to participating for two main reasons: partly because she had never 

before taken part in a research study, and partly because she thought that it would be 

worthwhile to try out a new car, since she would have to replace her 1991 Toyota Camry 

within the next 6 to 12 months and thought that this would be a good opportunity for an 

extended test drive. [We feel as though the latter was the predominant reason.] She 

mentioned several times that she enjoys the feel of Toyotas, and that Toyota and Lexus 

were the only cars that she liked when she had to “downgrade” from her big Cadillac in 

the early 90s. [This might be indicative of status or class, since Cadillac represents 

success and accomplishment to older individuals. It is particularly interesting that she 

mentioned her Cadillac several times without prompting. It would seem that the feel and 

comfort of the Prius invoked feelings of nostalgia for the comfort Nancy had enjoyed in 

her previous Cadillac.] 

Nancy was very eager to take part in the study, greeting us outside as we pulled up to her 

home. She also made multiple attempts to find a suitable plug for us to test when we the 

first plug that we tested didn’t work. When we suggested we may have to leave without 

placing the vehicle, she hurriedly (almost frantically) searched for another plug and even 

offered to have it fixed as soon as possible, saying, “My guy can be out here tomorrow!” 

[Her eagerness may be attributed to the fact that she was planning to go to Southern 

California, and had anticipated that she was going to take the much newer PHEV. Also, it 

is a new car that she could show off to her friends in Southern California. [We feel that 
 191 

how other people perceived the vehicle had a lot to do with why Nancy enjoyed it so 

much. We also feel that demonstrating the vehicle to her friends and showing the plug 

(something different from a regular Prius) also made the car more valuable to her.] 

The Beginning 

Nancy didn’t quite know what to expect from a PHEV when she signed up to take part in 

our vehicle demonstration. Having no experience with any hybrid vehicle, she seemed to 

struggle with the concept of how the car worked, and how it was different from a regular 

Prius. [When questioned at the final interview, she stated that she had expected to get 

good fuel economy, or, at least, better than with her own car. She assumed that the PHEV 

used less gas, but still wasn’t sure how it compared to a normal Prius, asking: “How does 

the regular one feel? Does it feel the same?”] 

After taking a brief test drive, she had many questions about the car such as: “How often 

do other people plug-in...Why would I use the screen?” [Referring to the Prius’ built-in 

Energy Monitor] and “What kind of fuel economy do other people get?” She was, 

however, quick to understand that using electricity could save her money on gasoline, 

and she exclaimed: “I am gonna plug this sucker in all the time!” 

As a single grandparent/caregiver living on a fixed income, Nancy feels as if costly 

gasoline expenditures limit her mobility. She has spent so much time at home raising her 

children and taking care of her grandchildren that she sometimes wants to be able to “just 

get up and go” on trips. This can prove challenging with her limited budget, or “one 

income,” as opposed to the two household incomes when she was married [and had a 

Cadillac]. Nancy doesn’t mind driving [as demonstrated by the 3000+ miles she put on 

the car during her trial month—she even laughed with joy when she was told how far she 

had driven], and, when asked, she took pleasure in listing off numerous places she had 

visited with the car on her trip to Southern California. Nancy admitted that the trip to 

Southern California was something she did only about twice a year, and it so happened 

that we had caught her at “just the right time.” She also noted that, if this had not been the 

case, she probably would have taken her own car on the trip, because she had her 

granddaughter with her and it would have been too expensive to purchase airplane tickets 
 192 

for the two of them. [Overall though, we feel that the mileage of this month’s driving was 

much higher than her standard month, especially since her usual driving is limited by the 

age of her vehicle, a 1991 Camry with 253,000 miles. Further evidence that this month 

was unrepresentative of her normal driving is that in the intervening week between 

relinquishing the PHEV and her final interview, Nancy reported that she had barely 

driven her Camry and referred to driving 30 miles to a large town in daunting terms as “a 

good drive.” Yet while she had the PHEV, she had driven almost every day, and within 2 

weeks, (when not driving to Southern California) had accumulated over 1,000 miles.] 

Nancy feels that that if she had a more reliable car, she would probably make similar trips 

more often. She is looking to move back to Southern California and believes that a good 

car would allow her to drive back up to visit her children and grandchildren. [This 

indicates that the extra driving isn’t so much because of better fuel economy—which she 

reported to be 37 mpg—but more because she had a new car for a short period of time 

and wanted to take advantage of it as much as possible. The gas savings were probably an 

added bonus for her.] 

Driving the vehicle 

Nancy told us that when driving the vehicle, she couldn’t feel or notice a difference 

between CD or CS operation. Nor was she aware of where the energy to move the vehicle 

was coming from. She repeatedly told us: “I am not sure when I’m using the gas or the 

battery.” However, she knew that by using the electricity or battery [this is how she 

referred to CD operation] she got “good mileage,” or boosted her fuel economy. She told 

us: “I’d rather use the battery, then you don’t have to fill up as much. The gas will last 

longer.” When asked how she knew this, she responded that she had a feeling that she 

was getting good mileage, based on how far she could go on $20.00 worth of gasoline. 

As a consumer, she feels she generally has an instinct for good value. For example, when 

she goes out to eat or purchases something from a store, she just knows when she is 

getting her money’s worth or a good deal. She did notice, or feel (on her trip to Southern 

California) that when in CS mode, the car still did “pretty good,” on fuel economy. 
 193 

While Nancy looked at the Energy Monitor, it didn’t really influence her driving. She 

saw the instantaneous mpg reading, but the numbers kept changing, anywhere from 17 

mpg to 99 mpg, and she found it too much to process. She was also confused about what 

the arrows meant, or what the display was telling her. She told us: “I watch [the screen], I 

try to watch [the screen]. I thought that I was getting it...but I think I am just confused.” 

Nevertheless, when asked if she would have altered her driving had she known what the 

display was telling her, she enthusiastically agreed, again saying that she would rather 

use electricity than gas because electricity is cheaper. The screen reminded Nancy of one 

of her former Cadillacs, which was able to change from 8 cylinders to 6 or 4 cylinders. 

She recounted how she would play with the accelerator to get the car to decrease the 

number of cylinders it was using. [We feel Nancy would have responded to very simple 

display, or if she was coached how she should drive the car to maximize fuel economy. 

During the first test drive we noticed that she accelerated quickly, did not coast, and 

drove rather fast—habits that are not conducive to good fuel economy.] 

Nancy understood that running the car on electricity wasn’t free, but she assumed that the 

cost wouldn’t be very high. When asked what she thought the cost was to charge the 

vehicle, she recalled that when she was given the PHEV, it was explained that the car, 

when charging, would use a similar amount of power as a toaster. She then paused and 

thought out loud saying: “Well I don’t know how much it would cost to run a toaster for 

8 hours; I hardly ever use a toaster.” However, despite her apparent lack of any frame of 

reference, she repeated that she didn’t think that it would be a lot, and she would be 

checking her electricity bill to make sure. [It would appear that the explanation that the 

researchers provided influenced her response.] Nancy usually compares her monthly 

PG&E bill to the bill from the corresponding month in the previous year. While this helps 

her budget, she also uses it to make sure everything in the house is working well. She 

recounted a story about one month when the current bill was much higher and her efforts 

to figure out what had happened to cause the increase. 

When asked about the vehicle, Nancy spoke mostly about the feel of car, and how it was 

different from her Camry. She mentioned that it was more comfortable and fit her better, 
 194 

was higher off the ground, quiet, had good air conditioning and a good stereo, was more 

reliable, and how “everyone liked [her new] car.” 

Charging 

Nancy found charging the PHEV to be very easy, both at home and on her trip to 

Southern California. While Nancy never encountered a problem charging, she really only 

looked for opportunities at the houses of friends and relatives where she was spending the 

night. At her own home she only charged at night. [Despite her flexible schedule, and the 

fact that she was at home during the day.] She was adamant that charging at night was the 

best way to go, calling herself a “nighttime charging gal.” [She seemed to be worried that 

if she plugged in during the day someone might unplug the car, or interfere with it, saying 

she was very cautious not to draw attention to the car.] Of the 18 times that Nancy 

charged the vehicle, she consistently did so after 5:00 pm, and usually between 8:00pm 

and 12:00am. The following is a time of day distribution of the start of recharging events 

for Nancy’s PHEV. 

 
 195 

There was one instance where plugging in was difficult because the outlet was far from 

the vehicle, but it worked because the 50ft cord just reached. She figured that there would 

have been more problems charging if the cord wasn’t so long, especially when she had to 

park on the street at night while staying in Lancaster. 

While looking for a place to charge, Nancy triggered an interesting social interaction. At 

a party hosted by her sister’s ex–sister-in-law (whom she hadn’t seen for 20 years), she 

asked to plug in. Despite not seeing her for 20 years, Nancy figured that the host 

wouldn’t mind her pulling in to the driveway and plugging in to the outlet in the garage. 

[We feel as though the party setting provided a platform for Nancy to “show off” her car 

and draw attention to the novelty of plugging-in.] 

Nancy seems to have fallen into a charging routing with the vehicle over the course of the 

month. However, it would appear that she couldn’t tell when the battery was depleted, 

telling us at the midterm and again at the final interview that she couldn’t tell when the 

car switched from CD to CS. [This is substantiated by the fact that she only charged 18 

times despite her wanting to run on electricity instead of gasoline.] 

However, at the final interview she was adamant that she only got her best mileage when 

the car was charged, and felt like on the long trip to Southern California she wasn’t doing 

as well because of how far she went without charging. [When asked, at the final 

interview, why she charged the car, she also noted that she had the impression that she 

was supposed to charge the car, otherwise what “would you [as researchers] have to 

study?”] 

When asked how often she charged the PHEV, Nancy responded that she charged it 

every day she used it except for two days, on one of which she simply just forgot. Later, 

she remembered and asked herself, “Why didn’t I charge?” But, she recalls that the car 

did “all right on gas” especially for driving through the hills. 

V2Green 

During the midterm, Nancy seemed to be very excited about the prospect of using the 

V2Green website to track her expenditures, in a similar way to her routine comparison of 
 196 

her electricity bills. However when asked at the final interview, Nancy hadn’t looked at 

the website. This despite the fact that she remembered that she had the tool and recounted 

how she had told people that she could go online and look at how the car was performing. 

Nancy believed that she was just too busy the last two weeks of the trial to look at site. 

When asked, she agreed that it would be nice to have similar information in the car. She 

explained that her grandson “bothers” her when she is at the computer, and makes it hard 

for her to concentrate, so an online system isn’t good for her. [A monthly paper report, 

like an addition to the electricity bill, would probably be more suitable and useful.]

Designing a PHEV 

In the design games Nancy choose a Toyota Prius as the base vehicle, which she then 

modified to a PHEV with a charge depleting range of 20 miles for the low cost, and 10 

miles, high cost scenarios. She chose to stick with a CD fuel economy of 75 mpg because 

it appeared to be in the middle range between what she was achieving and the highest 

mileage of 125 mpg. [Again, her experience and instincts as a bargain shopper may have 

taught her this philosophy.] 

While making the choices, Nancy says she was mainly looking to get the best for her 

money and was buying on a budget. She figured that a charge-sustaining fuel economy of 

75 mpg was pretty good. She did, however, choose to upgrade the charging time in every 

scenario to four hours. When asked why she chose this upgrade, she mentioned that it 

would be nice to be able to charge during the day. [This seems odd since she never 

charged the vehicle during the day, and identified herself as a nighttime charger.] When 

asked when she would picture herself charging during the day, she said that although she 

hadn’t previously done so [because she was worried about drawing attention to it], she 

would probably charge her car during the day if it only took four hours. Nancy felt that 

faster charging would have been helpful in her trip to Southern California, where she 

could have easily stopped for a couple of hours along the way to recharge the car. She 

went on to explain she would have chosen a period of 1 hour charging, but that it would 

have cost her too much more. [Based on how she used the vehicle, the extra money might 

have been better spent increasing CD range or CD/CS fuel economy.] When asked to 
 197 

compare the PHEV-conversion she drove to the vehicle she had built in the game, Nancy 

said she wasn’t sure which car was better. [This underscores a level of confusion about 

the vehicle on her part.] 

Several times throughout the interviews Nancy asked if she could purchase the PHEV she 

had used during the trial. She repeatedly said how much she liked the PHEV-conversion 

and that if she could afford it she would buy one immediately. It is unclear if Nancy was 

enamored with the PHEV being a new car, since her current car is an older model that she 

says has lost its comfort, or if she likes the technology and function of the PHEV. 

3. Octavia 

Summary Paraphrase 

“It is a great car that does everything I need, with no change in my driving. I was unsure 

at first how it worked—especially recharging. The more I learned, the more I felt I knew 

how to get the most out of it—recharge every day to reduce our dependence on oil.” 

The Start 

Octavia is a middle-aged woman who lives with her retired mother in an attached home 

and works as a librarian. She drives a Honda Civic, which she purchased a few months 

ago. She generally makes shorter trips (<20 miles). She was first attracted to AAA 

Northern California, Nevada & Utah’s recruitment letter because its sounded like a fun 

way to help researchers explore an important technology that held important implications 

for the environment and fuel use—what she considered to be a “worthy” cause—without 

requiring too much of her to participate. At first, she thought the study involved pure 

EVs, like the small, short-range EV owned by her neighbor across the street. Later, when 

she was told by phone that the vehicle would be a modified Prius, she was “intrigued” 

and anticipated that it would be more functional than the small EV she had in mind. 

In Part 1 of the questionnaire completed at the start of her PHEV trial, Octavia reported 

that she was not familiar with HEV, EV, or PHEV technologies and thought that a 

“hybrid-electric vehicle” could be plugged in to an electrical outlet. After further 
 198 

explanation of electric-drive technologies, she concluded that most current HEV buyers 

were driven by financial motives, whereas if she were to buy an HEV, it would be for 

environmental reasons. She believed that climate change is a real, human-caused problem 

that, along with air pollution and the nation’s dependence on foreign oil, requires urgent 

action. 

She was very eager when the PHEV was delivered; during the initial test drive she was 

very pleased with the amenities including the coldness of the air conditioning (she felt 

Honda wasn’t very good with climate controls). After the first lap around the block, she 

commented on the fuel economy, stating that she had “never gotten 70 mpg before.” 

However, she did seem unsure of the PHEV technology, and in particular wanted to 

know when to charge the vehicle and for how long. 

The Driving Experience 

During the study Octavia completely substituted the PHEV for her Honda Civic. Relative 

to her normal driving patterns, she felt that she did not change the frequency, distance, or 

destinations of her trips. She stayed within her “predictable” driving radius, and didn’t 

feel any need to modify her speed or driving routes. She was surprised the car performed 

“great” without any “compromise” for the added benefits of fuel economy. She felt the 

PHEV was quiet and smooth, although she did occasionally feel a “lurch” when the 

engine kicked in. When driving, Octavia focused on the mpg portion of the gauges, and 

found the indicators of electricity usage and battery state of charge to be more confusing. 

Octavia was surprised by the “phenomenal” increase in gas mileage relative to her Honda 

Civic—as well as the accompanying reductions in carbon emissions, which were “even 

better.” She said it was “fun to watch the thing,” seeing that she could drive 65 mph 

while getting 75 mpg. 

She filled up the PHEV only once during the month, whereas she believes she has to 

refill the Civic every ten days to 2 weeks. She was impressed that the PHEV fuel-level 

(gasoline) gauge “didn’t move” very much. Although Octavia acknowledged that she 

didn’t track or calculate fuel expenditures (“I don’t do that”), she believed that the $31 

she spent on gasoline for the month she had the PHEV was substantially less than the 
 199 

$100-125 she would normally budget (“in my head”) per month for gasoline costs. 

Although she did not know how much her electric bill would increase due to the vehicle, 

she reasoned that it could not be significant relative to the $75-100 she estimated for 

gasoline savings. (Note: In part 1 of the questionnaire, Octavia reported her monthly 

electric bill ranges from ~$60 to $110 dollars, and she consulted her bill to find that her 

per kWh rate is variable (12 to 23 cents) depending on the amount of electricity used.) 

For Octavia, using less gas “was a great feeling” because it “has got be a good thing.” 

She linked gas savings with energy independence and reducing environmental impacts. 

She said that in the world today “we have people dying...corruption and big 

business...due to the whole dependence on oil...we are in trouble...” creating “untenable 

situations for our country”; “we can’t keep going this way.” She felt that the PHEV 

gauges would help people make a stronger connection between their personal actions and 

such global problems. 

Learning Recharge Behavior 

Octavia only recharged at her home, parked in her driveway; she didn’t seek additional 

recharging locations. She didn’t feel a need for alternative locations because of the short 

distances of her trips (which never exceeded 20 miles). She also felt that home was a 

safer spot for recharging because she “[didn’t] want someone to take the cord.” 

Other than the location, Octavia did significantly adapt her recharge behavior over the 

course of the trial. During the first two weeks, she was unsure how to judge the battery’s 

state of charge and would plug-in for 3-5 hours every other day or couple of days. She 

was just “guessing” and didn’t follow a consistent pattern. She thought of recharging the 

vehicle as if it were a “cell phone.” [We did not probe further what this meant. I took it to 

mean that she thought of the car as providing whatever benefit it provided so long as the 

battery had some charge in it, much the same way you can place a phone call using your 

cell phone whether it is fully charged or half charged.] After being introduced to the 

V2Green website at the midterm interview she immediately saw that there was large 

potential for her to improve her gasoline mileage—that she “could do more.” She 

commented on how website information was something she hadn’t before “paid attention 
 200 

to,” and that she hadn’t been “scheduling [her] plug-in time based on that.” Although she 

stated that she was not a “numbers person” and was resistant to having to do any “math,” 

she was excited about the possibility for the website to help her improve gas savings. 

Over the last two weeks of the trial she logged in to the website every few days. 

She felt her understanding of the battery was further boosted a week later when she was 

instructed to read the PHEV “buyer’s guide” in preparation for the design exercises in the 

final questionnaire. She considers herself to be a “reader,” and felt that the handout and 

exercises helped her to finally “solidify” how to recharge the PHEV. With this 

information she said, “Now I get it...and I’m not charging it enough...I’m [switching] to 

gasoline half way through my day...I’m not utilizing the battery component...I need to 

start at 100% every day.” The handout helped her to pull together the information of how 

long it took to recharge the vehicle to maximize her gasoline savings. 

Octavia’s explanation of her learning process was corroborated by our records of her 

gasoline and electricity use (although she did not specifically describe her change in 

terms of mpg or electricity use over the month). She drove 280 miles over the first two 

weeks, averaging 50 mpg, with 32% of her miles in CD operation. At the mid-term 

interview, she estimated attaining at least 60 mpg, explaining that she would get over 40 

mpg in town, and between 65 and 90 mpg on the highway (she noted that these estimates 

are rough and that she “will never do anything mathematical to figure it out”). After 

receiving access to the V2Green website, she drove over 214 miles in the second two 

weeks and increased her average (gasoline-only) fuel economy to 60 mpg, and the 

proportion of CD miles doubled to 65%. In particular, over the last 6 days (70 miles) of 

her trial—after she had read through the PHEV buyer’s guide—she began to recharge 

almost every evening and achieved an average of 79 mpg with 100% CD driving. At the 

final interview she wished she could have had access the V2Green and buyers guide 

information from the very start of the trial. Given the big changes in recharging over her 

month, she agreed that her last week looked more like her prediction of her longer term 

driving and recharging than did her earlier weeks. 
 201 

Talking to People 

Over the course of her PHEV trial, many people interested in the vehicle approached 

Octavia. At work she was approached by security people and teachers that noticed the 

PHEV was not her normal car. Once Octavia explained the intent of the study to explore 

technology use, people were “really excited” particularly when she mentioned how many 

mpg she could get, such as 99.9 mpg going down a hill. People would ask if they could 

get in the study. A few people also noticed the car plugged in at her driveway, which 

initiated further conversations. She also took some friends for a test ride, at that the 

experience left most people “intrigued.” 

Future Vehicle Purchases 

In PHEV design games at the end of the trial, Octavia chose a Toyota Prius as her next 

likely vehicle purchase. In designing her own PHEV upgrades, she was not interested in 

improving recharge time lower than 8 hours because she could plug in at night (at home) 

most of the time. She also liked the idea of achieving 100 mpg in CD operation 

(particularly if it was “only $1000” more than the base 75 mpg option), as well as a 20 

mile CD range that would cover her roundtrip commute. In higher price scenarios 

Octavia was willing to reduce such upgrades in order to keep the “total price” down, 

although she feels she would need more time to fully contemplate such tradeoffs. 

In discussing the PHEV design exercise, Octavia admitted she didn’t understand some 

concepts. In particular, she was under the impression that all-electric operation meant the 

vehicle “won’t revert to the gasoline and you are more limited,” although she later 

pointed out the explanation in the PHEV guide that specifically said that AE operation 

did not mean the car was an electric vehicle. Octavia stated that clearer information was 

important to explain AE operation, where the researchers needed to reinforce that the 

vehicle is capable of accommodating everyday driving needs. Her “experience has not 

been with a [electric] vehicle like that in my entire life” and such a change would be a 

“leap.” Thus, she didn’t “have enough” information to understand that AER would be 

safe and reliable for her. 
 202 

At the close of the study, Octavia “really like[d] the Prius” and regretted having just 

bought a new Honda Civic a few months before without at least test driving a hybrid. She 

did consider a hybrid at the time, but due to cost issues and worries about the battery and 

how to dispose if it, she did not seriously pursue this option. In the future she would 

consider PHEV options, but she would have to further “ponder” about the specific 

attributes she would like, such AE vs. blended operation. She also noted that for a longerterm scenario, e.g., if she purchased a PHEV, she would likely seek out additional 

recharge opportunities beyond home, and potentially modify her driving behavior as 

required to further reduce gasoline usage.