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Operated by the Alliance for Sustainable Energy, LLC

This report is available at no cost from the National Renewable Energy

Laboratory (NREL) at www.nrel.gov/publications.

Contract No. DE-AC36-08GO28308

Technical Report

NREL/TP-6A20-73147

April 2019

California Time-of-Use (TOU)

Transition: Effects on Distributed Wind 

and Solar Economic Potential 

Ashwin Ramdas, Kevin McCabe, Paritosh Das, 

and Benjamin Sigrin

National Renewable Energy Laboratory
NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency & Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

This report is available at no cost from the National Renewable Energy

Laboratory (NREL) at www.nrel.gov/publications.

Contract No. DE-AC36-08GO28308

National Renewable Energy Laboratory

15013 Denver West Parkway

Golden, CO 80401

303-275-3000 • www.nrel.gov

Technical Report

NREL/TP-6A20-73147

April 2019

California Time-of-Use (TOU)

Transition: Effects on Distributed 

Wind and Solar Economic Potential

Ashwin Ramdas, Kevin McCabe, Paritosh Das, 

and Benjamin Sigrin

National Renewable Energy Laboratory

Suggested Citation

Ramdas, Ashwin, Kevin McCabe, Paritosh Das, and Benjamin Sigrin. 2019. California 

Time-of-Use (TOU) Transition: Effects on Distributed Wind and Solar Economic Potential. 

Golden, CO: National Renewable Energy Laboratory. NREL/TP-6A20-73147.

https://www.nrel.gov/docs/fy19osti/73147.
NOTICE

This work was authored by the National Renewable Energy Laboratory, operated by Alliance for Sustainable 

Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding 

provided by U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Wind and Water Power 

Program. The views expressed herein do not necessarily represent the views of the DOE or the U.S. Government.

This report is available at no cost from the National Renewable 

Energy Laboratory (NREL) at www.nrel.gov/publications.

U.S. Department of Energy (DOE) reports produced after 1991 

and a growing number of pre-1991 documents are available 

free via www.OSTI.gov.

Cover Photos by Dennis Schroeder: (clockwise, left to right) NREL 51934, NREL 45897, NREL 42160, NREL 45891, NREL 48097, 

NREL 46526.

NREL prints on paper that contains recycled content.
iii

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Acknowledgments

This work was supported by the U.S. Department of Energy (DOE) Wind Energy Technology 

Office under Contract No. DEAC36-08GO28308 with the National Renewable Energy 

Laboratory (NREL). The authors thank Ian Baring-Gould, Bret Barker, Michael Bergey, Patrick 

Gilman, Juliet Homer, Jennie Jorgensen, Jereme Kent, Eric Lantz, and Alice Orrell for their 

thoughtful reviews and other contributions. Opinions represented in this report are the authors’ 

own and do not reflect the view of the U.S. Department of Energy or the U.S. government. 

Any remaining errors or omissions are the sole responsibility of the authors.
iv

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List of Acronyms and Abbreviations

ATB Annual Technology Baseline

BANC Balancing Authority of Northern California

CAPEX capital expenditure

CEC California Energy Commission

CIPB Pacific Gas & Electric Bay Area Balancing Authority

CIPV Pacific Gas & Electric Valley Area Balancing Authority

CISC Southern California Edison Balancing Authority

CISD San Diego Gas & Electric Balancing Authority

CPUC California Public Utility Commission

CSBOE California State Board of Equalization

DER distributed energy resources

dGen Distributed Generation Market Demand

DNI direct normal solar irradiance

DOE U.S. Department of Energy

DPV distributed solar photovoltaics 

DW distributed wind

GW gigawatt

GWDC gigawatt-direct current

IID Imperial Irrigation District

kW kilowatt

LBNL Lawrence Berkeley National Laboratory

LDWP Los Angeles Department of Water & Power

MW megawatt

MWDC megawatt-direct current

NPV net present value

NREL National Renewable Energy Laboratory

REPLICA Rooftop Energy Potential of Low Income Communities in America 

SGIP Self-Generation Incentive Program

TRG techno-resource group

TOU time of use

URDB Utility Rate Database
v

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Executive Summary

Time-of-use (TOU) retail energy rates price electricity differently by the time of day, thereby 

communicating to consumers the costs of supplying electricity throughout the day. As a 

successor to volumetric rates, TOU rates are part of a broader movement to modernize demandside loads. In 2015, the California Public Utility Commission announced reforms to better align 

costs of electricity supply and demand. Most prominently, Decision D.15.07-001 initiated a 

transition to TOU tariffs for all residential customers, to begin implementation in 2019. An 

impact of the transition is the change in the value of distributed wind and solar generation, based 

on the correlation of each technology’s generation with retail prices. In part, this relative change 

in value under TOU could be considered an implication of the “duck curve”— as solar 

penetration in California increases, it depresses the price of midday generation and increases 

prices during afternoon peak load.

This study evaluates the impact of the pending enactment of the California TOU mandate on the 

economic attractiveness of behind-the-meter distributed wind and solar systems, both in isolation 

and after accounting for inter-technology competition. We assess attractiveness through

“economic potential,” a metric we define as the amount of generation capacity, both existing and 

hypothetical, that exceeds a specified rate of return (5.4%) and therefore would be economic to 

construct. In addition, we identify cost improvements needed for a robust (i.e., 1-gigawatt [GW]) 

distributed wind market and the specific counties and sectors with substantial wind and solar 

economic potential. To assess the TOU impact, we compiled all non-TOU and (opt-in) TOU 

rates currently offered by utilities, with the presumption that the to-be-announced rates will be 

comparable to today’s opt-in rates. The pre-TOU and TOU rates are also normalized under the 

presumption that the transition will result in the same amount of revenue collected, or 

alternatively that the average cost of electricity to consumers remains constant. 

Implications of TOU Transition on Distributed Wind and Solar Economic Potential

Over the scenarios considered, model results indicate there are realistic pathways to reaching a

1-GW distributed wind market in California (Figure ES-1, next page), though solar economic 

potential was found to be substantially larger than that of wind potential. Distributed wind’s 

capacity factor does not appear to be strongly correlated to the periods of peak electricity prices 

as set by utility’s TOU periods. Because of this disassociation and nuances in the billing of tiered 

electricity, the transition to TOU is projected to moderately decrease distributed wind economic 

potential and increase that of distributed solar. However, a limitation of this analysis is that it 

does not factor in the change in rate values as California works toward its goal of 100% 

renewables. As variable renewable energy penetration increases to meet this goal, our results 

suggest that wind generation will become increasingly correlated to periods of peak electricity 

prices. Increased variable renewable penetration, especially of solar, is likely to shift periods of 

higher electricity demand to later in the evening, and any periodic adjustments in TOU periods to 

reflect these new periods of demand will positively affect the value of wind generation more than 

the value of solar generation.

In addition to capital costs and retail electricity prices, two techno-economic factors were found 

to have a significant impact on distributed wind economic potential: the assumed statutory 

expiration of state (i.e., California) and federal incentives, and gradual improvements in solar 

panel efficiency. 
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Figure ES-1. Economic potential of distributed wind (top row) and solar (bottom row) by sector

Commercial and Industrial sectors are on mandatory TOU rates prior to 2019.

Sensitivity of Distributed Wind Economic Potential to Capital Cost Reductions

High distributed wind capital costs are a significant barrier to large-scale adoption, and they 

impact economic potential more than the transition to TOU rates, according to our model. 

To understand potential returns to government research, development, and demonstration 

expenditures, we explore the sensitivity of capital cost reductions on distributed wind economic 

potential (Figure ES-2, next page). We find that distributed wind economic potential increases 

substantially in 2020 for capital costs below $3/W—particularly for residential- and commercialscale turbines; capital costs must fall below $2/W in 2030 to support a significant increase in 

economic potential, in large part due to the expected continued cost reductions in solar. We 

identified an upper limit to the state’s behind-the-meter distributed wind economic potential 

at approximately 5 GW that is due to inherent turbine siting challenges as well as the spatial 

distribution and quantities of load. 
vii

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Figure ES-2. Economic potential of distributed wind versus system cost in 2030,

by turbine class (left axis) and in aggregate (right axis)

Geographic Trends in DER Economic Potential

Several geospatial factors affect the geographic distribution of economic potential. Under our 

TOU Baseline scenario, which assumes reference capital costs and that TOU rates are in effect, 

the regions of California that exhibit the most economic potential in 2030 were Southern 

California, namely San Bernardino County and Los Angeles County, and counties including and 

surrounding San Joaquin County in central California. Solar economic potential is also highest in 

Southern California, with the most potential being projected in Los Angeles County. At costs of 

$1/W, Los Angeles, San Bernardino, and Riverside counties could see noteworthy increases in 

their distributed wind economic potential.

Overall, California exhibits over 1 GW of economic potential for distributed wind by 2030, even 

with the moderate decrease in potential under TOU. This potential is represented mostly by 

Southern California, which sees the most notable increase in economic viability as capital 

expenditure prices decline. Figure ES-3 and ES-4 show the geographic distribution of economic 

potential as well as underlying data that feeds into the economic potential estimations.

Limitations of This Analysis

Our analysis investigates the economic viability of distributed wind and distributed solar; we

do not attempt to project deployment or adoption. Though we attempt to model the value of 

distributed wind and distributed solar generation as variable renewable energy penetration 

increases, we neither incorporate the technical limitations of variable renewable energy nor 

model energy storage in this analysis. Additionally, as mentioned above, our analysis relies on 

the currently available TOU rates and presumes the eventual default TOU rates will be similar.
viii

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Figure ES-3. County maps of California highlighting the following statistics: (a) total (all sectors 

and turbine classes) distributed wind economic potential (megawatts [MW]) in 2030 for the TOU 

Baseline scenario, (b) wind resource at 80-m hub height, (c) annual electricity consumption, and 

(d) distributed wind siting availability
ix

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Figure ES-4. County maps of California highlighting the following statistics: (a) total (all sectors) 

distributed solar economic potential (MW) in 2030 for the TOU Baseline scenario, (b) solar 

resource strength, (c) annual electricity consumption, (d) and distributed solar siting availability

Note the difference in scale between the distributed solar and distributed wind economic potential map.
x

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Note

The Time-of-Use (TOU) peak periods used in this analysis for Southern California Edison (SCE) 

were based off of the optional residential TOU rates and the mandatory commercial and 

industrial TOU rates offered as of September 12, 2018. As of April 12, 2019, SCE’s two new 

residential TOU rates shifted the on-peak period from 2-8 p.m. to 4-9 p.m. or 5-8 p.m. As of 

March 1, 2019, SCE’s new commercial and industrial TOU rates shifted the on-peak period from 

12-6 p.m. to 4-9 p.m. This analysis is unable to assess the impact of the revised tariffs on the 

economic potential of distributed wind and solar. The TOU peak periods for the Pacific Gas & 

Electric (PG&E) and San Diego Gas & Electric (SDG&E) rates used in this analysis are aligned 

with the currently offered TOU rates by these utilities.
xi

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Table of Contents

1 Introduction........................................................................................................................................... 1

2 Methodology ......................................................................................................................................... 1

2.1 Model Updates .............................................................................................................................. 1

2.1.1 Implementation of New Data Sets.................................................................................... 1

2.1.2 Representation of California Time-of-Use Mandate........................................................ 2

2.1.3 Competition Among Distributed Generation Technologies............................................. 3

2.2 Scenario Analysis Framework....................................................................................................... 4

3 Results................................................................................................................................................... 6

3.1 Implications of TOU Transition.................................................................................................... 6

3.1.1 Economic Potential of Distributed Wind and Distributed Solar ...................................... 6

3.1.2 Examination of Distributed Wind Economic Potential Decline Under TOU ................ 10

3.2 Effect of Cost on Distributed Wind Potential ............................................................................. 14

3.2.1 Potential of Distributed Wind in a Noncompetitive and Competitive Environment...... 15

3.2.2 Potential of Distributed Solar in a Noncompetitive and Competitive Environment ...... 17

3.2.3 Sensitivity of Distributed Wind Potential to Opportunistic Cost Improvements........... 19

3.3 The Value of Distributed Wind and Distributed Solar Generation with Increased Variable 

Renewable Resource Penetration ................................................................................................ 21

3.3.1 Value of Generation ....................................................................................................... 21

3.3.2 Change in Value of Generation...................................................................................... 22

3.4 Geospatial Trends in Distributed Generation Potential............................................................... 23

3.4.1 Economic Potential ........................................................................................................ 24

3.4.2 Wind Resource ............................................................................................................... 24

3.4.3 Electrical Load ............................................................................................................... 25

3.4.4 Siting Availability .......................................................................................................... 26

3.4.5 Effects of Capital Cost Reductions on Distributed Generation Potential....................... 28

4 Conclusion .......................................................................................................................................... 30

References................................................................................................................................................. 32

Appendix A. Economic Potential Results............................................................................................... 34

Appendix B. Distributed Wind Capital Costs ......................................................................................... 35

Appendix C. Economic Potential Results............................................................................................... 37

Appendix D. Value of Generation............................................................................................................ 38

Appendix E. Change in Value of Generation.......................................................................................... 40
xii

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List of Figures

Figure ES-1. Economic potential of distributed wind (top row) and solar (bottom row) by sector............. vi

Figure ES-2. Economic potential of distributed wind versus system cost in 2030, by turbine class 

(left axis) and in aggregate (right axis) .................................................................................. vii

Figure ES-3. County maps of California highlighting the following statistics: (a) total (all sectors and 

turbine classes) distributed wind economic potential (megawatts [MW]) in 2030 for the TOU 

Baseline scenario, (b) wind resource at 80-m hub height, (c) annual electricity consumption, 

and (d) distributed wind siting availability ...........................................................................viii

Figure ES-4. County maps of California highlighting the following statistics: (a) total (all sectors) 

distributed solar economic potential (MW) in 2030 for the TOU Baseline scenario, (b) solar 

resource strength, (c) annual electricity consumption, (d) and distributed solar siting 

availability............................................................................................................................... ix

Figure 1. Effect of TOU mandate on economic potential of distributed wind.............................................. 7

Figure 2. Effect of TOU mandate on economic potential of distributed solar.............................................. 7

Figure 3. Breakdown of distributed wind economic potential (left) and number of projects (right) by 

turbine size (kW) in 2030......................................................................................................... 8

Figure 4. Economic potential of distributed wind (top row) and distributed solar (bottom row) by sector 10

Figure 5. A sample load profile from a summer weekday for a Southern California Edison customer in 

San Bernardino overlaid with average summer generation in San Bernardino with a 10-kW 

wind system............................................................................................................................ 12

Figure 6. Overlay of net electricity demand (left axis), hourly rates for a wind system under tiered rates 

(right axis), and no wind system under tiered rates (right axis)............................................. 12

Figure 7. Comparison of cumulative bills for a wind system under TOU and a wind system under a tiered 

rate structure........................................................................................................................... 13

Figure 8. Overlay of residential TOU tiers with summer (left) and winter (right) capacity factor profiles 14

Figure 9. Economic potential of distributed wind in the TOU Baseline and TOU High Cost Wind 

scenarios with no solar competition....................................................................................... 16

Figure 10. Economic potential of distributed wind in the TOU Baseline and TOU High Cost Wind 

scenarios with solar competition............................................................................................ 17

Figure 11. Economic potential of distributed solar in the TOU High Cost Solar, TOU Baseline, and TOU 

Low Cost Solar scenarios with no wind competition............................................................. 18

Figure 12. Economic potential of distributed solar in the TOU High Cost Solar, TOU Baseline, and TOU 

Low Cost Solar scenarios with wind competition.................................................................. 18

Figure 13. Economic potential of distributed wind versus system cost in 2020 by turbine class (left axis) 

and compiled as a total (right axis) ........................................................................................ 20

Figure 14. Economic potential of distributed wind versus system cost in 2030 by turbine class (left axis) 

and compiled as a total (right axis) ........................................................................................ 20

Figure 15. Difference between the value of wind generation and the value of solar generation, by county

................................................................................................................................................ 22

Figure 16. Difference between the percent change in generation value from 2020 of solar and wind....... 23

Figure 17. Total (all sectors and turbine classes) economic potential (MW) in 2030 for the TOU Baseline 

scenario—wind (left) and solar (right)................................................................................... 24

Figure 18. Average wind speed (m/s) at 80-meter hub height in (left) and DNI (kWh/m2

/day) (right)..... 25

Figure 19. Average wind speed (m/s) at 30-meter hub height.................................................................... 25

Figure 20. Projected annual electricity consumption (GWh) for all (residential, commercial, 

and industrial) customers in 2030 .......................................................................................... 26

Figure 21. Favorability for siting availability for wind (left) and solar (right)........................................... 27

Figure 22. Map of tract-level solar siting availability for the southern and eastern Bay Area ................... 28

Figure 23. Change in economic potential relative to the TOU Baseline scenario results for the TOU High 

Cost Solar scenario (left), $1/W scenario (middle), and $0/W scenario (right)..................... 29
xiii

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List of Tables

Table 1. TOU Rates Used in the Study......................................................................................................... 3

Table 2. Distributed Wind Capital Cost Scenarios ....................................................................................... 5

Table 3. Full Scenario Matrix, Including Scenario Names, Wind and Solar Cost Schedules, and the Rate 

Case Used in Each Scenario..................................................................................................... 5

Table 4. CAPEX for Distributed Wind Under the TOU Baseline and TOU High Cost Scenarios in 2030 15

Table 5. Projected Installed Capacity Upon Which the Hourly Wholesale Electricity Prices are Based ... 21

Table A-1. Economic Potential Results by Technology and Scenario in Megawatts................................. 34

Table B-1. Distributed Wind Capital Costs by Cost Scenario in $/kWDollars per Kilowatt for the Baseline 

Scenario.................................................................................................................................. 35

Table B-2. Distributed Wind Capital Costs by Cost Scenario in $/kWDollars per Kilowatt for the High 

Scenario.................................................................................................................................. 36

Table C-1. Economic Potential Results by Turbine Class of Capital Cost Sensitivity Analysis in 2020... 37

Table C-2. Economic Potential Results by Turbine Class of Capital Cost Sensitivity Analysis in 2030... 37

Table D-1. Value of 10,000 kWh of Generation by Technology by Year.................................................. 38

Table E-1. Change in Value of 10,000 kWh of Generation by Technology by Year................................. 40
1

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1 Introduction

Costs of supplying electricity vary substantially by the time of day, location, and the portfolio of 

generation resources serving a system. However, the price signals that consumers (i.e., demand) 

are exposed to are typically different from the cost of generation (i.e., supply). Instead, most 

residential retail tariffs are structured around a desire for simplicity to the consumer and an 

assumption of low elasticity of demand. Several factors—particularly the rise of zero marginal 

cost solar and wind generation—motivate a realignment of the demand and supply price signals.

Starting with AB 327 in 2013 and continuing with Decision D.15.07-001 in 2015, the California 

Public Utility Commission initiated a series of regulations seeking to reform residential 

electricity rates to better align costs of electricity supply and demand. Most prominently, 

Decision D.15.07-001 initiated a transition to time-of-use (TOU) tariffs for residential customers, 

though it also instituted measures to consolidate residential electricity tiers and implemented a 

minimum electricity bill. Though the final TOU rates are not yet publicly available, they are 

expected to result in higher prices during periods of peak system demand (e.g., afternoons and 

evenings, particularly in the summer) and lower prices during off-peak hours when demand is

lower. Notably, periods of peak demand coincide with hours of lower solar irradiance, so 

transition to TOU tariffs will not only affect how much California consumers pay for electricity 

throughout the day but also the value of distributed wind and solar generation. 

This study seeks to understand the impact of the pending enactment of the TOU mandate on the 

economic attractiveness of behind-the-meter distributed wind and solar systems in California for 

residential, commercial, and industrial sectors. We assess attractiveness through the economic 

potential of distributed wind and solar, a metric of the amount of generation capacity—both 

existing and hypothetical—that exceeds a specified rate of return and therefore would be 

economic to construct. We define “economic potential” of distributed generation here as the 

amount of capacity that could be installed and achieve a positive net present value (NPV) using 

a 5.4% weighted average cost of capital over its lifecycle, inclusive of capital and operation and 

maintenance costs, savings on retail electricity costs, applicable incentives, and tax implications. 

Using this definition, we project the cost competitiveness of distributed wind and solar through 

2030 for each sector and by county with retail grid-sourced electricity under the TOU mandate 

as compared to a counterfactual scenario in which current residential rates are extended. 

We use the NREL Distributed Generation Market Demand (dGen) model (Sigrin et al. 2016; 

Lantz et al. 2016), an agent-based model of distributed energy resources (DER) adoption to 

project the technical and economic potential of behind-the-meter distributed wind and solar 

in California. The dGen model simulates the resource, economics, siting, load, and policy 

conditions for thousands of potential distributed wind and solar sites across California. 

We use these methods and data to answer the following research questions:

• What are the implications of TOU retail tariffs in California for the economic 

competitiveness of behind-the-meter distributed wind and solar in 2030? A better 

alignment of retail prices with costs of wholesale generation, particularly with increased 

solar penetration, should influence the value of distributed generation, and thus the intertechnology financial attractiveness.
2

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• What level of cost and performance improvement would be needed for a robust 

California distributed wind market when accounting for distributed solar competition?

Though California’s high retail electricity prices and supportive DER policy both 

contribute to the viability of distributed wind, siting difficulties and historically high 

capital costs both challenge the maintenance of a dynamic distributed wind market. 

We examine the level of cost reduction needed for a “robust” 1-gigawatt-direct-current 

(GWDC) market and discuss its feasibility.

• In which regions and sectors of California are distributed wind already competitive with 

distributed solar? Which areas are the first to emerge as competitive? The emergence of 

new technologies depends on niches where the emerging technology provides superior 

value over the status quo. Specific counties, sectors, or end uses could provide such 

niches, and thus allow the distributed wind market to scale over time. 

California has a rich history of policy actions influencing the economic viability of DERs. Here 

we summarize two macro trends: policies incentivizing the deployment of DERs and historical 

changes in retail electricity in the state.

Starting in 1997 with the implementation of the Emerging Renewables Program and other 

follow-on programs—including the Self-Generation Incentive Program (SGIP) and the 

California Solar Initiative—California has a long history of state-level support for DERs. The 

primary goal of these programs has been to develop a self-sustaining market for renewable 

energy in distributed generation applications (Go Solar n.d.). These include programs directed 

at single-family and multifamily buildings as well as low-income populations. The SGIP is still 

in effect statewide for distributed wind, and several incentives for solar are available at select 

utilities; for example, the statewide Single-Family Affordable Solar Homes rebate program is 

still active as of the time of publication.

Complementing these incentives, California’s retail electricity prices are among the highest in 

the United States. Of note is the “tiered” structure of residential rates, where the increasing 

marginal cost of consumption disproportionately incentivizes the reduction of consumption for 

high-consumption households through distributed generation and energy efficiency. Rates are 

also structured to promote equity in the energy burden, where users in different climate regions 

are assigned a “baseline” daily consumption that ensures equal monthly energy costs across 

climate regions. Decision D.15.07-001 is expected to reduce the number of tiers and the variance 

of price between tiers, which would have a distributional influence on DER economics for 

different consumers. 

By a combination of high retail prices and supportive policy, California leads the nation in 

deployment of DERs. Through September 2018, over 9,300 megawatts-direct current (MWDC)

of residential and nonresidential solar had been deployed (Wood Mackenzie 2018). Despite these 

favorable conditions, distributed wind deployment in California remained at 70 MW through 

2017 (DOE 2018). Research has identified multiple additional barriers to distributed wind 

deployment, including siting challenges in urban areas (Lantz et al. 2016) and high capital and 

operation and maintenance costs (DOE 2018) that inhibit industry scale-up and cost reduction. 

Other factors include expensive permitting, a lack of property tax exclusions for distributed wind 

as distributed solar (CSBOE 2008), and differences in the availability of incentives for 

distributed wind and distributed solar. Also, McCabe et al. (2018) demonstrated that these factors 
3

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are not spatially uniform and can result in conditions favorable to distributed wind development 

in targeted regions. As the penetration of distributed and utility-scale solar increases, grid 

integration issues are likely to come to the forefront; for example, the “duck curve” phenomenon

(Denholm et al. 2015; Denholm, Clark, and O’Connell 2016) increases ramping requirements, 

shifts net peak load (and prices) later in the day, and increases curtailment during periods of 

excess variable generation. These phenomena could increase the value of distributed wind 

generation relative to that of distributed solar. 

Results in this report are based on modeling and are subject to refinement. First, though the 

transition to TOU rates will begin in 2019,

1 the exact policy details were unavailable to the 

authors at the time of publication. Such details include definitions of the TOU periods and their 

electricity prices. Considering this uncertainty, we assume the enacted TOU rates will be 

comparable to the voluntary opt-in TOU tariffs already available today and that the TOU 

transition will be revenue-neutral (i.e., that the average cost of electricity pre-TOU and postTOU is constant). Second, following NREL practice, we assume all currently enacted policies 

will expire per their statutory authority. For instance, many of the state and federal policies 

modeled are currently scheduled to expire between 2020 and 2024, though in practice, they could 

be renewed or modified in other meaningful ways. Finally, this analysis is relatively static in that 

it does not consider future evolution of retail electricity rates in California, for example, as 

a result of increasing utility-scale renewable energy deployment. However, many studies 

(Darghouth et al. 2016; Denholm, Clark, and O’Connell 2016; Mills and Wiser 2012) have 

indicated that the increasing deployment of solar and wind generation will affect both the 

absolute cost of electricity and the timing of peak electricity price. 

The remainder of the report is organized as follows. Section 2 details the methodology used, 

including model specification, the scenarios examined, and technology capital cost trajectories. 

Section 3 presents the results of the three research questions listed above, specifically, the 

projected implication of TOU transition on distributed wind and solar technical potential, how 

the potential varies by future capital cost assumptions, and analysis of the regions and sectors 

that are most favorable for distributed wind and solar. Finally, Section 4 provides a discussion 

of the results and our conclusions. 

 

1 Under Decision 18-05-011, roll out of mandatory TOU rates has been delayed until October 2020 for Pacific Gas 

and Electric and Southern California Edison customers.
1

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2 Methodology

As stated in the Introduction, we use the agent-based dGen model to project the technical and 

economic potential of behind-the-meter distributed wind and solar in California. The dGen 

model simulates the resource, economics, siting, load, and policy conditions for millions of 

potential distributed wind sites across the country. dGen agents use a discounted cash flow 

framework to evaluate in each year whether it is more economic to continue to consume gridsourced electricity or adopt a distributed wind or solar system. For this analysis, 100 agents 

were sampled per county sector, which is equivalent to 17,400 agents for the entire state. 

This analysis uses the v2018 dGen model as documented in Cole et al. (2018). Further 

documentation of the wind- and solar-specific modules are available in Sigrin et al. (2016), 

McCabe et al. (2018), and Lantz et al. (2016). Four specific modifications were made to 

v2018 dGen for this analysis: 

• Incorporation of California-specific data sets

• Incorporation of the Rooftop Energy Potential of Low Income Communities in America

(REPLICA) data set on rooftop solar technical potential (Mooney and Sigrin 2018)

• Representation of cost-competitiveness between distributed wind and solar

• Updated parameters for retail electricity tariffs, both pre-TOU and post-TOU and for 

distributed wind capital costs.

These improvements in data fidelity constitute a significant overhaul to the model and provide 

a basis for calculating county-level economic potential estimates for distributed wind and solar 

under a scenario analysis framework.

2.1 Model Updates

2.1.1 Implementation of New Data Sets

Through an agreement with the California Energy Commission (CEC), we implemented several 

new California-specific data sets that improve model specification. Of special importance is an 

improvement in electrical demand data by county, sector, and utility for 1998–2017. This data 

set is complemented by CEC hourly load shape data2 for five major utilities in California3, which 

are representative of single-family and multifamily load profiles and usage levels in the 

residential sector and eight distinct building types in the nonresidential sectors. Together, these 

additional data improve constraints on the county-sector annual electrical demand, the load 

shapes, and the resulting fidelity of economic potential estimates for this analysis.

The REPLICA data set is another new data set we implemented in dGen. This data set provides 

estimates of residential rooftop solar technical potential at the census tract-level that are stratified 

by income, building type, and tenure. Similar to the CEC-provided load data, REPLICA data 

provide a better understanding of the census tract-level and sector-level constraints for building 

 

2 Our analysis assumes daily load profiles of electricity demand are inelastic to time changes in pricing. However, 

(EPRI 2008) indicates that TOU pricing may result in changes to temporal electricity usage. 3 Los Angeles Department of Water & Power, Pacific Gas & Electric, Sacramento Municipal Utility District, San 

Diego Gas & Electric, and Southern California Edison
2

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

counts and rooftop potential by using lidar-based scans of the building stock in major 

metropolitan regions of California (Gagnon et al. 2016; Sigrin and Mooney 2018).

2.1.2 Representation of California Time-of-Use Mandate

In July 2015, the California Public Utility Commission issued Decision D.15.07-001, which 

provides direction to the California investor-owned utilities regarding the specific steps to reform 

residential electrical rates (CPUC 2018). Described henceforth as the TOU Mandate, this 

regulation resulted in default TOU rates to begin in 2019. The mandate is germane to the 

residential sector as nonresidential users are already mandated to subscribe to TOU-based rates. 

However, the exact policy details were unavailable to the authors at the time of publication; these 

include definitions of the TOU periods and their electricity prices. Given this uncertainty, we 

assume the enacted TOU rates will be comparable to voluntary opt-in TOU tariffs already 

available today in terms of the hours and price of each TOU period. We also assume the TOU 

transition will be revenue-neutral (i.e., that the average cost of electricity pre-TOU and postTOU is constant).

To simulate the TOU transition we collected data on current residential non-TOU, residential 

opt-in TOU, and nonresidential TOU rates using the Utility Rate Database (OpenEI 2018). To 

ensure full coverage, we identified five unique rates for each utility, including one for residential 

customers, two for commercial customers, and two for industrial customers, where the two 

nonresidential rates are for low-demand and high-demand customers. The exact value that 

delineates low- and high-demand customers depends on each individual utility’s current tariffs 

and is not constant across all utilities. For the residential sector, we assume customers are not 

limited by any demand constraints placed on the residential TOU rate by the utility, and therefore 

are only represented by a single rate. Finally, where coverage is lacking (e.g., small municipal 

and cooperative utilities), we selected representative rates based on geographical distance to the 

nearest investor-owned utility. Table 1 includes a sample of these representative TOU rates.4

 

4 Default TOU rate periods and pricing structure had not been announced at time of analysis on September 12, 2018. 

Any changes to policy after this date including changes or announcements of the default TOU periods were not 

incorporated in this report.
3

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Table 1. TOU Rates Used in the Study

Utility Name Sector Minimum

Demand (kW)

Maximum 

Demand (kW) Rate Name

Pacific Gas 

and Electric Residential 0 N/A E-TOU Option B not dependent on location

Pacific Gas 

and Electric Commercial 0 75 A1 – TOU

Pacific Gas 

and Electric Commercial 75 500 A10 Primary Voltage TOU

Pacific Gas 

and Electric Industrial 500 1,000 E19 Primary Voltage TOU

Pacific Gas 

and Electric Industrial 1,000 N/A E20 Primary Voltage TOU

San Diego 

Gas & Electric Residential 0 N/A TOU-DR Inland Baseline Region

San Diego 

Gas & Electric Commercial 20 200 AL-TOU Primary

San Diego 

Gas & Electric Commercial 200 500 AL-TOU Primary

San Diego 

Gas & Electric Industrial 500 1,000 AL-TOU Primary

San Diego 

Gas & Electric Industrial 1,000 N/A AL-TOU Primary

Southern 

California Edison Residential 0 N/A D-A

Southern 

California Edison Commercial 20 200 GS-2 TOU A at 220 kV

Southern 

California Edison Commercial 200 500 GS-3 TOU A at 220 kV

Southern 

California Edison Industrial 500 1,000 TOU-8

Southern 

California Edison Industrial 1,000 N/A TOU-8

2.1.3 Competition Among Distributed Generation Technologies

We consider the simultaneous cost-competitiveness of distributed wind and solar, relative to 

each technology and versus continuing to purchase grid-sourced electricity. Our comparison of 

technologies only considers economic factors, specifically, the 20-year NPV of the distributed 

generation system. In actuality, additional factors might influence consumer technology 

adoption, including familiarity with a technology, whether peers have adopted it, visual 

appearance, hassle, and perceived risk—though these factors are not considered here.

For the sake of comparability, agents with identical attributes are used to evaluate each

technology. These include siting availability of each technology, wind and solar resource profiles
4

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at the site, load profiles, and retail rates. For instance, this reflects that distributed wind might not 

be feasible at a particular urban site, whereas solar might be. 

A technology is deemed “competitive” only if its normalized NPV is positive. If one technology 

is competitive, it is the sole technology selected; if both technologies have a negative normalized 

NPV, neither is selected. If both technologies are competitive, Equation 1 (next page) is used to 

determine the market share for each technology. For the sake of comparability, the NPV is 

normalized by the system capacity (NPV/kW), because sites could differ in their technical 

potential.

Let MMww and MMss be the market shares of wind and solar respectively and NNNNVVww and NNNNVVss their 

normalized NPV, and then:

(1) MMww = NNNN ww

2

NNNN ww

2 + NNNN ss2

(2) MMss = NNNN ss

2

NNNN ww

2 + NNNN ss2

The mathematical properties of Equations 1 and 2 are twofold. First, the technology with the 

greater economic5 return will increase market share at a quadratic rate, such that consumer 

preference converges when the NPVs are substantially different. Second, the equations avoids a 

“knife edge,” so that one technology is not wholly ignored if it has a marginally-worse NPV than 

the other technology. This formulation reflects the concept that consumers prefer technologies 

with better economic returns but might still adopt a technology with inferior economic return 

(though at lower rates).

2.2 Scenario Analysis Framework

We use a scenario-based approach to identify the relative effect of the TOU transition on the 

long-term economic outlook for distributed wind and solar in California. The scenarios are not 

intended to be prescriptive, but they provide an array of plausible future market conditions to 

explore sensitivities of economic potential. Though several sensitivities could be considered, 

our analysis uses distributed generation capital costs and rate design as the primary sensitivities 

of interest. 

Cost and Performance Scenarios for Distributed Generation Technologies

Distributed wind and solar cost and performance projections, which were developed based on 

a combination of current market data, were designed to explore a range of plausible market 

outcomes. For distributed wind, two distributed capital costs projections were developed

(Table 2). The High scenario is based on the Reference cost projection from Lantz et al. (2016).

Since 2016, distributed wind capital cost reductions have progressed faster than anticipated in 

previous reports, necessitating a new Mid cost schedule. Three methods were used to better align 

 

5 Our analysis only compares the economic potential of technologies to determine market share; it does not

incorporate consumer behavioral aspects that would affect the potential adoption of either technology.
5

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our capital expenditure (CAPEX) schedules with non-public data available to NREL on current 

distributed wind projects:

• Applying a 15% cost reduction from the Breakthrough (Deployment) cost projection 

from Lantz et al. (2016) for turbines below 50 kW

• Matching the NREL 2018 Annual Technology Baseline (ATB) (NREL 2018) TechnoResource Group (TRG) 4 schedule for land-based wind for turbines that are 1.5-MW 

and greater

• Making a proportional adjustment from the 1.5-MW schedule to turbines sized from 

50 kW to 1 MW, using the ratios from the Breakthrough (Deployment) cost projection.

Table 2. Distributed Wind Capital Cost Scenarios

Schedule Name Description

High Reference values from the Lantz (2016)

Mid CAPEX schedules for turbines that 1.5 MW and greater follow the ATB TRG 4 

schedule.

Turbines below 50 kW are priced at 15% reduction from Breakthrough values from 

Lantz (2016).

Turbines that are between 50 kW and 1 MW are proportioned from the 1.5-MW 

schedule using Breakthrough value ratios.

For distributed solar, three cost scenarios were used; the Low and Mid Cost scenarios are from 

the ATB (NREL 2018), and a High cost scenario is mostly based on the 2018 Tracking the Sun

report from Lawrence Berkeley National Laboratory (Barbose and Darghouth 2018). The High 

Cost Solar cost schedule follows the same trajectory as the Mid Cost scenario, but it is uniformly 

35% higher than the Mid Cost price for each year. The 35% mark-up is made to align the 2018 

solar capital costs with those reported for California in 2018 (i.e., from the Tracking the Sun

report). For both technologies, external to the cost and performance assumptions, we have also 

included a scenario in which the TOU mandate is in effect, and a counterfactual scenario in 

which non-TOU rates persist, to better understand the effect of TOU tariffs on each technology’s 

economic viability.

Table 3. Full Scenario Matrix, Including Scenario Names, Wind and Solar Cost Schedules, 

and the Rate Case Used in Each Scenario

Scenario Name Wind Cost Schedule Solar Cost Schedule Rates

Baseline Mid 2018 ATB Mid Current rates, no TOU

TOU Baseline Mid 2018 ATB Mid TOU on in 2020

High Cost Wind High 2018 ATB Mid Current rates, no TOU

TOU High Cost Wind High 2018 ATB Low TOU on in 2020

TOU High Cost Solar Mid 2018 LBNLa High TOU on in 2020

TOU Low Cost Solar Mid 2018 ATB Low TOU on in 2020

a Lawrence Berkeley National Laboratory (Barbose and Darghouth 2018).
6

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3 Results

For this case study, we analyze the economic potential of wind and solar in California under 

various cost and electricity rate scenarios. A primary goal of this study is to understand the 

effects of TOU rates on the intra-technology economic potential of distributed wind and solar. 

Additionally, we identify the effects of capital cost on wind’s economic competitiveness by 

linearly varying the capital cost of wind relative to solar costs. Finally, we identify the specific 

regions (counties) and sectors in California that are particularly competitive for one 

technology—with the aim of understanding where initial markets might develop.

3.1 Implications of TOU Transition

3.1.1 Economic Potential of Distributed Wind and Distributed Solar

Our model projects that the economic potential of distributed wind could decrease when shifting 

from the current tiered rate structure to a non-tiered TOU rate structure; however, distributed 

solar may experience an increase in economic potential. 

Under the Baseline scenario, distributed wind sees modest, yet notable, competitiveness with 

distributed solar. From 2019 to 2021, distributed wind economic potential drops to around 

180 MW before consistently growing to just under 1.5 GW by 2030. The initial drop in wind

economic potential can be attributed to the reduction and expiration of the federal investment tax 

credit from 2018 to 2022 as well as the expiration of California’s Self-Generation Incentive 

Program by the end of 2020. The subsequent growth to 1.5 GW is a result of the continued 

decline in CAPEX for distributed wind in all turbine sizes. 

The implementation of TOU rates in our TOU Baseline scenario has a slight negative impact on

the economic competitiveness of distributed wind as seen in Figure 1 (next page). Distributed 

wind with and without TOU experience similar trends of dropping from 2019 to 2021 before 

increasing in economic potential. With TOU implementation, however, wind economic potential 

reaches just over 1.3 GW by 2030, compared to 1.5 GW under current rate structures. Though 

distributed wind experiences a minor decrease in economic potential, our results indicate that 

over 1 GW of potential still exists in California by 2030. On the other hand, TOU provides a 

small improvement in distributed solar economic potential relative to the Baseline, as shown in 

Figure 2 (next page). Distributed solar economic potential in our TOU Baseline scenario grows 

at a slightly higher rate than the Baseline scenario. In 2030, distributed solar under TOU 

surpasses 44 GW, which is about 800 MW higher than the Baseline scenario. 

Although the economic potential for distributed wind is lower than it is for solar, and its 

competitiveness decreases modestly with TOU, a noteworthy number of distributed wind 

projects with economic viability still exists in California. The 1.3 GW of economic potential that 

our model projects in 2030 corresponds to roughly 80,000 distributed wind projects (Figure 3). 

When breaking these projects down by system size, it becomes evident that smaller-sized 

turbines comprise a clear majority of the projects. More specifically, turbines sized from 2.5 kW

to 20 kW constitute less than one-third of the 1.3 GW of economic potential but amount to over 

70,000 projects. See Appendix A for the full economic potential results by year, scenario, and 

technology.
7

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Figure 1. Effect of TOU mandate on economic potential of distributed wind

Figure 2. Effect of TOU mandate on economic potential of distributed solar
8

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Figure 3. Breakdown of distributed wind economic potential (above) and number of projects 

(below, next page) by turbine size (kW) in 2030
9

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Because we model commercial and industrial customers to already subscribe to a TOU rate, the 

only change in economic potential in the TOU Baseline scenario occurs in the residential sector

(Figure 4, next page). The residential sector sees distributed wind potential of roughly 550 MW 

by 2030 in the Baseline, which reduces to just over 400 MW in the TOU Baseline scenario. The 

economic potential of distributed solar in the residential sector improves from 15.5 GW to 16.2 

GW in 2030. Next, we explain the opposing reactions to TOU implementation by examining 

how each technology responds to the TOU rate structures as compared to the current tiered rate 

structures. 
10

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Figure 4. Economic potential of distributed wind (top row) and distributed solar (bottom row) 

by sector

3.1.2 Examination of Distributed Wind Economic Potential Decline Under TOU

Contrary to our expectation, the TOU periods and rates as modeled in our study do not seem to 

substantially affect distributed wind economic potential. This directional conclusion is based 

on nuances of current rates and could vary based on the final tariffs and the specific load profiles 

of individual customers. We explain the effect of the TOU transition with two phenomena—first, 

wind generation actually exhibits only a modest correlation with the TOU peak periods6 and, 

second, the effect of changes away from daily-tiered rates is larger than the effect of TOU 

period correlation.

For current residential tiered rates, the tier into which a customer falls in each hour depends 

on the customer’s total electricity usage up until that hour; once the customer’s daily baseline 

allowance is reached, subsequent consumption in that day is billed at the next tiered rate. A 

customer’s hourly usage is calculated based on their net electricity consumption from energy 

coming in minus any excess energy going out. Owning a distributed generation system would 

allow a customer to reduce their hourly net energy usage, thus decreasing their cumulative 

energy usage and delaying their entry into a higher-tiered rate. Avoiding higher tiers results 

 

6 TOU rate periods modeled in this analysis are reflective of TOU options offered by utilities as of September 12, 

2018. Any changes to policy after this date, including changes or announcements of the default TOU periods were 

not incorporated in this report.
11

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in bill savings. By reducing the net load in each hour, a distributed wind system can delay or 

avoid higher tiers under the current rate plan.

Compared to mechanism of savings explained above, a distributed wind system under TOU does

not provide an advantage in California because of the low wind capacity factors and the

misalignment of electricity prices and wind resource potential. For distributed wind to be 

valuable under TOU, it must generate during peak periods to maximize bill savings; the TOU 

peak periods are set time intervals in the evening which align with the utility’s higher electricity 

demand. In contrast to tiered rates, the hourly rates for TOU do not shift based on a customer’s 

usage; they are set rates for set periods. Additionally, TOU prices are higher in summer months 

than winter months to correspond with higher seasonal demand. In general, our mesoscale wind 

resource data indicate that residential wind capacity factors in California are lower in summer 

months than winter months. Equally significant is that in summer months, wind has a higher 

capacity factor in the night and early morning, and it trails off before the evening hours. 

Subsequently, distributed wind has lower generation during the peak periods and lower

generation overall during the months with higher rates. The TOU rates do not allow wind to take

noteworthy advantage of nighttime or early morning generation, but the current tiered rates do.

Under the current tiered rates, which depend on a customer’s usage, nighttime and early morning 

wind generation can push back the onset of higher-tiered rates to later hours, after some hours of 

peak evening demand have already taken place. Thus, with hours of higher demand billed at a 

lower rate with a wind system than without one, the current tiered rates allow a distributed wind 

system to offer greater savings than TOU rates.

7

To illustrate this phenomenon, below are three figures that depict a sample day for an Southern 

California Edison customer with a 10-kW wind system. In Figure 5, the load profile is from a 

single summer weekday in San Bernardino County, and the wind profile is the average hourly 

summer capacity factors for San Bernardino County.

8 We use Southern California Edison’s

baseline allowance for San Bernardino County, while the prices for the tiered structure and TOU 

structure were chosen such that the cumulative daily bill would be equal in the two structures 

with no distributed wind system. By equalizing the rates without a wind system, we can directly 

observe the effect of the distributed wind system’s performance and rate design on the 

cumulative bill. 

Figure 6 shows tiered rates with and without the 10kW system as well as net electricity demand. 

Distributed wind’s early generation pushes back the hour when the higher-tiered rate kicks in, 

allowing higher demand to be priced at a lower value. This figure also illustrates the relationship 

between demand and pricing for TOU, specifically that high demand still aligns with TOU peak 

period prices because wind generation is not strong in those hours. Figure 7 shows that with 

tiered rates, the customer’s total bill for the day was roughly $20, compared to about $24 under 

TOU rates.

 

7 Results may vary if multitiered rate structures are used in tandem with TOU. 8 San Bernardino County was chosen for this example because it has a notably high number of installations of

10-kW systems (Folkman et al. 2016).
12

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Figure 5. A sample load profile from a summer weekday for a Southern California Edison

customer in San Bernardino County overlaid with average summer generation in San Bernardino

County with a 10-kW wind system

Figure 6. Overlay of net electricity demand (left axis), hourly rates for a wind system under tiered 

rates (right axis), and no wind system under tiered rates (right axis)

TOU hourly rates with and without a system (right axis) are equal.
13

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Figure 7. Comparison of cumulative bills for a wind system under TOU and a wind system under a 

tiered rate structure

Bills with no wind systems are equal under the two rate structures.

Distributed wind under TOU becomes more advantageous than current tiered rates at higher 

capacity factors; however, the generally lower capacity factors for wind in California keep it 

from significantly avoiding the cost of on-peak prices, therefore tipping the scale in favor of 

current tiered rates. 

On the other hand, distributed solar can take advantage of higher capacity factors and the periods 

of the day when capacity factors rise. As illustrated in Figure 8, solar generation predominantly 

occurs in the “off-peak” period, but depending on the utility’s defined TOU periods, solar can 

still generate substantially in the “on-peak” hours.
14

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Figure 8. Overlay of residential TOU tiers with summer (left) and winter (right) capacity factor profiles

3.2 Effect of Cost on Distributed Wind Potential

Each agent in dGen evaluates a distributed solar system, distributed wind system, or no system at all. The competitive nature of this 

selection can make it less clear how cost affects the economic potential of distributed wind. To better understand the effect of cost on 

the economic viability of distributed wind the TOU Baseline and TOU High Cost Wind scenarios were run with no solar competition. 
15

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

In these scenarios, the agents only evaluate a distributed wind system or no system at all; 

distributed solar is not presented as an option. By modeling distributed wind with no solar 

competition and under the same rate structure, we can isolate for how distributed wind capital 

cost affects its economic potential. Additionally, comparing these results to our original results 

will provide a better understanding of how competition with distributed solar affects the market 

for distributed wind. The model was also run for distributed solar with no distributed wind 

competition under the TOU Baseline, TOU High Cost Solar, and TOU Low Cost Solar 

scenarios. 

3.2.1 Potential of Distributed Wind in an Environment with and 

without Competition

The cost of energy relative to that of distributed solar is a critical driver of the economic 

competitiveness of distributed wind. In an environment where distributed wind does not compete 

with distributed solar, the economic potential in the TOU Baseline scenario reaches about 

7.5 GW in 2030. Table 4 details the system CAPEX in 2030 that were used in the TOU Baseline

scenario compared to the TOU High Cost Wind scenario (See Appendix B for the full annual 

CAPEX schedules used in this analysis for distributed wind). With the CAPEX in the TOU High 

Cost Wind scenario, the economic potential is reduced by almost 75% from the TOU Baseline

scenario. These results, in Figure 9, underscore the heavy dependence of distributed wind 

viability on the cost of installation for all turbine sizes.

Table 4. CAPEX for Distributed Wind Under the TOU Baseline and TOU High Cost Scenarios

in 2030

Turbine Size (kW) TOU Baseline CAPEX

in 2030 ($/kW)

TOU High Cost Wind CAPEX

in 2030 ($/kW)

2.5 3,391 7,923

5 2,763 6,515

10 2,320 5,520

20 2,006 4,816

50 1,489 3,497

100 1,489 3,231

250 1,489 2,680

500 1,489 2,417

750 1,489 2,263

1,000 1,489 1,960

1,500 1,381 1,818
16

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Figure 9. Economic potential of distributed wind in the TOU Baseline and TOU High Cost Wind 

scenarios with no solar competition

When introducing distributed solar competition, the importance of cost becomes even more 

apparent for distributed wind (Figure 10). Because of the higher system cost per W relative 

to distributed solar and lower capacity factors, distributed wind relinquishes over 6 GW of 

economic potential in the TOU Baseline scenario in 2030. Higher costs for wind further suppress 

its economic potential. Under the TOU High Cost Wind cost schedule with solar competition, 

distributed wind reaches only 250 MW of economic potential in 2030, followed by a drop and 

slow rise to 150 MW by 2050.
17

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Figure 10. Economic potential of distributed wind in the TOU Baseline and TOU High Cost Wind 

scenarios with solar competition

3.2.2 Potential of Distributed Solar in a Noncompetitive and 

Competitive Environment

The economic potential of distributed solar, when competing with distributed wind, does not 

deviate as notably from the results with no competition, because distributed wind captures less 

than 1.5 GW of economic potential at any given point (Figures 11, 12). Even with high solar 

costs and competition from distributed wind, the economic potential of solar drops only 2.6 GW 

from its previous value of 45 GW with mid costs and no competition. 
18

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Figure 11. Economic potential of distributed solar in the TOU High Cost Solar, TOU Baseline, 

and TOU Low Cost Solar scenarios with no wind competition

Figure 12. Economic potential of distributed solar in the TOU High Cost Solar, TOU Baseline, 

and TOU Low Cost Solar scenarios with wind competition
19

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

3.2.3 Sensitivity of Distributed Wind Potential to Opportunistic 

Cost Improvements

The dGen model projects at least 1 GW of distributed wind economic potential by 2030. To 

grow this market, a decline in system CAPEX is needed. To evaluate the sensitivity of market 

growth to additional cost reduction, we assess the change in economic potential as lower total 

CAPEX are assumed. We focus first on the results in 2020 and second on the results in 2030. 

As shown in Figure 13 (next page), economic potential seems to proliferate in 2020, when costs 

decline below $3/W. A reduction from $4/W to $3/W appears to double the economic potential 

of the residential sector turbines, and a reduction from $3/W to $2/W doubles the economic 

potential for the residential sector again to just over 1 GW. The commercial class of turbines 

follows the same trajectory as the residential class, while the sum of all turbine classes follows 

the same trend as both classes, where the economic potential grows rapidly when prices decline 

below $3/W. The decline in price has little effect on the larger sized systems, because these 

systems are already priced below $2/W. The total economic potential in California reaches 

4.4 GW at prices of $2/W in 2020.

The reduction in CAPEX is paramount for distributed wind to become increasingly competitive.

For comparison, our ATB Mid Cost schedule prices the CAPEX of distributed solar at $2.30/W

for the residential sector and $1.63/W for the commercial and industrial sectors in 2020. Even at 

$2/W for residential wind, the distributed wind economic potential of 4.4 GW falls well below 

that of distributed solar (37 GW), as underlying variables such as siting availability, load 

demand, and wind resource potential constrains further viability. 

Further reductions in price are needed in the years after the federal investment tax credit expires. 

By 2030, a price of $2/W results in a marginal increase in total economic potential, as it is driven 

by a growth in the residential class of turbines (Figure 14, next page). Economic potential only 

significantly grows when prices decline below $2/W, due in large part to the forecast of 

continued cost reductions in solar. For example, in 2030, our ATB Mid Cost schedule prices the 

CAPEX of distributed solar at $1.49/W for the residential sector and $1.12/W for the commercial 

and industrial sectors.

For reference, the average cost of an 8.9-kW turbine deployed in 2017 was $10.76/W while the 

average for a 90-kW turbine in 2017 was $4.67/W (Orrell 2018). To reach the $2/W target, 

CAPEX prices for the 8.9 kW turbine must decline 67% over a span of 13 years, or 12%

annually. The 90-kW turbine cost must decline 6% annually to reach $2/W in 2030. See 

Appendix C for the values from this analysis.
20

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Figure 13. Economic potential of distributed wind versus system cost in 2020 by turbine class 

(left axis) and compiled as a total (right axis)

Figure 14. Economic potential of distributed wind versus system cost in 2030 by turbine class 

(left axis) and compiled as a total (right axis)
21

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

3.3 The Value of Distributed Wind and Distributed Solar Generation 

with Increased Variable Renewable Resource Penetration

As deployment of utility-scale and distributed-scale wind and solar increases in California, the 

time-value of electricity, as realized through wholesale electricity prices, will continue to evolve

to reflect the cost of supplying electricity. Most projections of capacity expansion indicate that 

a majority of the new renewable capacity will come from solar (Brinkman et al. 2016). In turn, 

electricity generation during periods of low solar irradiance—particularly during the late 

afternoon-evening ramp—increases in value (Mills 2016). We expect TOU periods to 

periodically adjust to better reflect the changing hours of peak pricing.

To understand the implications of increasing renewable penetration on long-term intertechnology competition, we examine changes in the value of residential wind generation and 

solar generation for three five-year intervals from 2020 to 2030. Our approach is to use modeled 

forecasts of California wholesale electricity prices and analyze how the evolution in wholesale 

prices would affect distributed wind and solar generation value if these were the price signals 

used to compensate DER systems. Specifically, the annual generation value of a residential wind 

system is estimated at the county level by taking the sum product of capacity factor at a 30-m 

hub height and projected hourly wholesale electricity prices. This sum product is then 

normalized by the total annual capacity factor and multiplied by 10,000 kWh, to estimate the 

value of 10,000 kWh of annual energy production from a distributed wind system in each 

county. The same value is calculated for solar using solar capacity factors and the same 

wholesale electricity prices. That is, the calculation is capacity-agnostic, as we are interested in 

the value of generation. Note that this is a hypothetical example and should not be interpreted 

as a forecast of future retail policy nor advocating for policy design.

3.3.1 Value of Generation

For this analysis, we incorporate a projection of hourly wholesale prices by balancing authority 

for 2020, 2025, and 2030. These wholesale prices are simulated outputs of the production cost 

model used in the California Low Carbon Grid Study (Brinkman et al. 2016), which were

amended for this study to reflect a scenario in which California reaches 100% renewable energy 

generation by 2045. The installed solar and wind capacities (Table 5) reflect a least-cost capacity 

expansion to reach 100% renewable generation and all operational grid requirements. In this 

scenario, solar capacity is projected at 59.6 GW and wind at 10.0 GW in 2030.

Table 5. Projected Installed Capacity Upon Which the Hourly Wholesale Electricity Prices 

are Based

Year Total Installed Solar

Capacity (MW)

Total Installed Wind

Capacity (MW)

2020 31,863 6,292

2025 47,868 6,512

2030 59,598 10,036
22

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Based on the capacity expansion forecast used here, the value of residential wind generation 

tends to increase in most of California over time, largely as a function of increasing solar 

penetration. In Figure 15, we have mapped the relative value between solar generation and wind 

generation by county; the color scale represents how much more valuable 10,000 kWh of 

generation from one technology is than the other in terms of dollars. As seen in this figure, the 

number of counties where distributed wind generation is more valuable that of distributed solar 

grows from 17 counties in 2020 to 22 counties by 2025. Four of these new counties emerge in 

Southern California and two counties arise in central California. Only one county in north central 

California switches from being more valuable for wind generation to more valuable for solar 

generation in 2025. In 2030, the new counties where distributed wind generation becomes more 

valuable surround the Bay Area, while Central California and Southern California remain 

strongholds for wind. Overall, 8 of the 40 counties that were more favorable for distributed solar 

generation in 2020 switch to being more favorable for distributed wind generation by 2030. See 

Appendix D for the complete values of generation used to create Figure 15.

Figure 15. Difference between the value of wind generation and the value of solar generation,

by county

DW = distributed wind, DPV = distributed solar photovoltaics

3.3.2 Change in Value of Generation

Most counties where residential solar energy is more valuable than wind energy in 2020 remain 

more valuable in 2030. However, though a unit of energy generated by solar remains more 

valuable than energy generated by wind in those counties, the shift from 2020 to 2030 improved

the value of wind more positively than the value of solar in almost every county. Figure 16

illustrates the relative change in value of distributed wind generation and distributed solar 

generation from 2020 to 2025 and from 2020 to 2030, where the color scale represents the 

difference on a percentage basis. In almost all counties, the value of residential wind energy

increases more than the value of residential solar energy as solar penetration increases.

Residential solar generation only increased in value relative to wind in Los Angeles County and 
23

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Tuolumne County in 2030. See Appendix E for the percentage change in value from 2020 by 

technology that was used to create Figure 16.

Figure 16. Difference between the percentage change in generation value from 2020 of solar and 

wind

3.4 Geospatial Trends in Distributed Generation Potential

McCabe et al. 2018 have demonstrated the close relationship of the economic viability of 

distributed wind and several key geospatial factors. In particular, data layers that represent the 

wind resource, end-use load, and siting availability all contribute to inform areas of elevated 

economic potential within a given state or region. Unique to our analysis, is the competition 

aspect of two distributed generation technologies: distributed wind and distributed solar. In this 

section, we examine the effect of each of these layers on the economic viability of distributed 

wind and solar specifically in California.

The estimates of economic potential represent the amount of distributed wind capacity that could 

be deployed at a positive NPV (calculated over the life of the facility) in a given year, using a 

weighted average cost of capital of 5.4% in each scenario. In addition, these estimates exclude 

parcels that do not conform to the siting restrictions applied in each scenario and are limited to 

the amount of on-site electrical load. Though previous sections have shown the time-dependent 

nature of economic potential—including the effects of changing capital costs, load growth, 

expiration of policies and incentives, and escalation of retail rate prices—the heat maps9 in 

subsequent sections show the potential for a static moment in time. Unless otherwise noted, 

2030 is used as the default analysis period.

 

9 Borrowing from the precedent set by McCabe et al. (2018), these maps are colloquially referred to as heat maps, 

though the more accurate description would be choropleth maps.
24

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3.4.1 Economic Potential

For the TOU Baseline scenario, the aggregate statewide amount (i.e., all sectors and turbine 

classes) of distributed wind economic potential in 2030 is just over 1,300 MW. Conversely, the 

aggregate statewide amount of distributed solar economic potential in the same year is just over 

44,000 MW. Figure 17 summarizes the 2030 economic potential results at the county level.

Figure 17. Total (all sectors and turbine classes) economic potential (MW) in 2030 for the 

TOU Baseline scenario—wind (left) and solar (right)

Note the difference in scale values.

3.4.2 Wind Resource

The state-level resource (Figure 18) informs the ultimate amount of distributed generation 

economic potential in California. However, when considered independently, resource alone is 

not necessarily a strong indicator of the economic viability of a distributed generation project—

other geospatial factors contribute to the final estimate of economic potential in a given county.

However, from a state-level perspective, the disparity between the overall resource strength for 

distributed wind and distributed solar in California appears to strongly correlate with the total

economic potential for each technology. Figures 18 and 19 show the state-level resource map for 

each technology: direct normal solar irradiance (DNI; kWh/m2

/day) for solar and wind speed 

(m/s) at 80 m and 30 m. The figures show a larger degree of spatial variance in wind resource 

than in solar resource in the state.
25

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Figure 18. Average wind speed (m/s) at 80-meter hub height in (left) and DNI (kWh/m2/day) (right)

Figure 19. Average wind speed (m/s) at 30-meter hub height

3.4.3 Electrical Load

The relationship between electrical load and economic potential is fairly straightforward in that 

distributed generation technologies are deployed proportionately to on-site energy consumption. 

The amount of load in each county in California reflects both the number of customers (i.e., 

residential homes, commercial buildings, or industrial sites) and the per capita energy usage 

of each customer. Though the electrical load is technology-agnostic, the county-level map 

demonstrates a strong spatial correlation not only with known population centers in the state but 

also with the amount of economic potential for both distributed wind and solar. Figure 20 shows 

the map of electrical load by county in 2030.
26

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Figure 20. Projected annual electricity consumption (GWh) for all (residential, commercial, 

and industrial) customers in 2030

Major metropolitan centers in California include areas collocated with the cities of Los Angeles, 

Riverside, San Bernardino, and San Diego in Southern California; Fresno in the San Joaquin 

Valley; and Sacramento, San Francisco, Oakland, and San Jose in Northern California. Each of 

these areas correlates with counties of higher electrical load as depicted in Figure 20, including 

Los Angeles County, San Bernardino County, Fresno County, Santa Clara County, and 

Sacramento County, among others. In many cases, these exact counties exist as areas of elevated 

economic potential as shown in Figure 20, which demonstrates the strong linkage between the 

two data layers.

3.4.4 Siting Availability

Though load and resource inform areas of increased favorability for distributed generation 

technologies, site-level exclusions can limit potential project development and therefore 

economic potential. Figure 21 provides visualizations of the siting availability for both 

distributed wind and solar. As discussed in McCabe et al. (2018), we simulate siting restrictions 

via two proxy variables: the average parcel area as a proxy for turbine setback from property 

lines and the level of tree canopy cover. Figure 21 (next page) shows the percentage of all 

turbine configurations considered in dGen that could be sited in a given parcel (i.e., unique 

combinations of turbine capacities and hub heights). Lower values represent either areas where 

siting constraints could prohibit development or areas in which no buildings exist.

A similar visualization was created to show an equivalent metric for distributed solar, though 

there are differences in the metrics. Siting limitations for solar are mostly defined by the 

suitability of the rooftop and are typically less stringent than those for distributed wind. Figure 

21 shows the modeled siting availability for solar, which is defined as the proportion of “solar-
27

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suitable”10 buildings to the total building count for each census tract. Importantly, solar siting 

availability shares a key characteristic with wind siting availability, in that areas with no 

buildings are represented as unsuitable (e.g., 0% siting availability).

Figure 21. Favorability for siting availability for wind (left) and solar (right)

Wind siting availability is represented by the proportion of the total number of turbine configurations available for 

siting at each parcel and solar siting availability by the total portion of “solar-suitable” buildings relative to the total 

building count for each census tract.

For distributed solar projects, the siting constraints have very little effect on the favorability for 

siting in nearly all parts of the state. We see lower percentages of the siting availability metric 

in only (1) areas with high concentrations of commercial or industrial sites and (2) highly dense 

urban areas in which the roof characteristics themselves (e.g., overly shaded, non-southward 

facing, area-limited) prohibit extensive development. Figure 22 represents a subset of the solar 

siting availability map in Figure 21, in which the broader Bay Area is shown—the tip of the San 

Francisco Peninsula, an area of high building density, shows lower values of solar siting 

availability.

For distributed wind projects, similar trends can be seen in areas of high population density—in 

particular, the major metropolitan regions named in Section 3.3.3. However, the map of siting 

availability for distributed wind statewide shows much more nuance and considers the morestringent aspects of siting wind projects on parcels that may be area-limited or canopy coverlimited—including areas that may exist outside those with a high population density. Conversely, 

parts of the state that are considered to have more area for development (i.e., larger parcel sizes) 

show greater availability for siting wind projects. These trends are reflected in the maps of 

economic potential for each distributed generation technology, where the economic potential of 

solar more closely follows areas of higher load with little restriction and the economic potential 

of wind is limited in areas of high population density and therefore low siting availability.

 

10 See Sigrin and Mooney 2018 for a discussion of solar suitability.
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Figure 22. Map of tract-level solar siting availability for the southern and eastern Bay Area

3.4.5 Effects of Capital Cost Reductions on Distributed Generation Potential

While the preceding sections highlight the intricate relationship between key geospatial layers 

and the economic potential of distributed generation technologies, Section 3.2 more broadly 

described the positive effect of a non-geospatial trend—the reduction of capital costs. Adding 

the effect of reduced costs as an additional “layer,” we can discern other geospatial trends in the 

viability of distributed wind. In particular, reducing capital costs allows us to visualize which 

areas in the state can be “unlocked” and could see an increase in distributed wind viability.

Figure 23 shows the incremental change in economic potential relative to the TOU Baseline

scenario for an increased competitiveness scenario (TOU High Cost Solar) and two reduced 

cost scenarios ($1/W and $0/W).
29

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Figure 23. Change in economic potential relative to the TOU Baseline scenario results for the 

TOU High Cost Solar scenario (left), $1/W scenario (middle), and $0/W scenario (right)

In the TOU High Cost Solar scenario, where distributed wind costs remain the same but 

distributed solar costs are higher than in the Baseline case, there is very little incremental change 

in the economic potential statewide. This result indicates that solar capital costs are already low 

enough that a 35% markup from the Mid cost schedule does not improve wind’s economic 

competitiveness. However, as we decrease wind to cost targets that solar has traditionally 

adopted (e.g., $1/W), the economic viability of wind increases dramatically. In the $1/W

scenario, several of the counties that showed elevated potential in the Mid case more than double 

in value. And in the hypothetical bounding case of $0/W wind, many more counties show similar 

increases and new counties are introduced into higher tiers of economic potential. We include 

this scenario for better understanding of the maximum potential of counties in California, less the 

effects of any operation and maintenance costs, poor wind resource, small electrical load, and 

unavailable siting conditions.
30

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4 Conclusion

In this analysis, we studied the relative competitiveness of DER technologies in California 

through three topics: the implications of TOU retail tariffs on the economic potential of behindthe-meter distributed wind and solar through 2030, the level of cost improvement needed for a 

competitive distributed wind market, and the regions and sectors where distributed wind is 

already competitive or is emerging as competitive.

Comparing our Baseline scenario (current non-mandatory TOU rates) to our TOU Baseline 

scenario, our results show that extending TOU rates to all residential customers decreases the 

economic viability of distributed wind in California. Though the commercial and industrial 

sectors remain the same because of their existing TOU rate requirement, cumulative distributed 

wind economic potential for the residential sector in 2030 decreases by 150 MW, from roughly 

550 MW of economic potential with the current tiered rate structure to just over 400 MW with 

TOU. The economic potential of all sectors decreases from just under 1.5 GW with tiered rates 

to a little over 1.3 MW with TOU rates in 2030. We attribute this dip in performance to the 

mismatch between TOU peak periods and wind’s performance throughout the day. Though TOU 

tariffs decrease distributed wind economic potential, our model equates the 1.3 GW of potential 

to over 80,000 economically viable distributed wind projects. Distributed solar improves from a 

total of 43 GW of economic potential in 2030 with tiered rates to roughly 44 GW under TOU 

implementation as a result of stronger overlap between peak periods and production.

Though distributed solar demonstrates greater economic potential than distributed wind, 

residential wind generation gains more value than solar generation as increased solar penetration 

alters the time value of electricity generation. Counties around the Bay Area and in Southern 

California emerge as places where wind generation has a higher value than solar generation as 

solar penetration increases. Furthermore, even in counties where solar generation remains more 

valuable, the change in value of residential wind generation is higher than the change in value 

of residential solar generation by 2030 in all but two counties.

For distributed wind to become competitive with distributed solar, CAPEX for wind must 

continue to fall. System costs must fall below $3/W by 2030 for wind to gain in economic 

competitiveness, but a reduction to below $2/W is needed to increase the economic potential 

significantly. Another barrier to distributed wind’s growth is the continuing decline in distributed 

solar prices, which are at less than $1.50/W by 2030 in our model.

Under our TOU Baseline scenario, the counties in California that exhibit the most distributed 

wind economic potential in 2030 lie in Southern California, namely San Bernardino County and 

Los Angeles County. Another pocket of elevated potential exists in counties east of the San 

Francisco Bay and at the northern tip of the San Joaquin Valley. Distributed solar exhibits 

highest economic potential in similar regions as distributed wind, including much of Southern 

California and counties south and east of the Bay Area. 

Several geospatial factors feed into the economic viability of distributed generation technologies, 

namely resource potential, electrical load, and siting availability. The overall higher resource 

potential for distributed solar manifests itself in its thirty-fold larger economic potential than 

distributed wind. Distributed wind also faces much higher siting constraints, mainly because of 
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high population density, property area limits, and canopy cover. In general, counties with high 

electrical load emerge as counties with the highest economic potential for both technologies.

Though our study offers an in-depth analysis of distributed wind economic potential in 

California, opportunities for further work exist to improve the accuracy of our results. 

Improvements to the underlying data include more-resolved load shape data for all utilities, 

more-detailed insight into future TOU tariff structures for when all sectors are on default TOU 

rates, and new wind power curves and wind resource data to represent the latest distributed wind 

turbine technology. Improvements to our method of assigning rates to customers are also needed. 

Our model has uniform rates for all customers within a utility, and it assigns a customer to a 

utility based on who serves their geographical location. But the major investor-owned utilities

also have unique prices and baseline allowances for each geographical service region within the 

utility. Adding such a layer of geographical resolution would allow us to more-accurately 

represent the price of electricity for all customers in varying locations. In addition to the 

improvements in our input data, assessing the opportunity of front-of-the-meter distributed 

wind could further illuminate the economic potential of distributed wind in California.
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This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

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This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Appendix A. Economic Potential Results

Table A-1. Economic Potential Results by Technology and Scenario (MW)

Baseline TOU Baseline High Cost Wind TOU High Cost Wind TOU High Cost Solar TOU Low Cost Solar

Year Wind Solar Wind Solar Wind Solar Wind Solar Wind Solar Wind Solar

2018 2,144.1 38,622.1 2,144.1 38,622.1 856.7 39,057.5 856.7 39,057.5 2,243.1 36,654.3 1,832.6 40,324.9

2019 2,480.0 38,510.1 2,470.7 38,719.7 990.4 39,043.9 994.0 39,242.8 2,550.5 36,205.1 2,047.3 40,731.7

2020 2,044.0 39,324.5 2,026.9 39,497.6 463.6 39,958.4 467.7 40,108.5 2,086.8 37,342.2 1,654.1 41,145.5

2021 176.3 41,572.4 170.7 41,996.9 30.5 41,668.1 31.4 42,081.1 177.0 40,027.7 146.8 44,059.5

2022 316.1 41,044.9 289.0 41,486.3 51.6 41,219.6 53.9 41,636.0 307.1 39,211.0 249.1 43,706.8

2023 424.4 41,423.7 386.0 41,991.1 63.3 41,668.3 66.7 42,210.7 406.6 39,900.4 336.0 44,163.9

2024 532.2 40,778.3 482.7 41,333.4 71.7 41,086.8 73.9 41,613.6 519.5 39,252.8 418.4 43,477.7

2025 903.8 41,869.8 819.7 42,340.0 134.7 42,403.8 129.3 42,842.3 864.9 40,628.6 716.7 44,562.2

2026 1,022.4 42,018.8 934.0 42,453.6 164.7 42,635.3 158.0 43,037.0 985.9 40,840.5 819.1 44,789.9

2027 1,067.8 41,967.3 961.0 42,505.6 170.1 42,617.1 159.8 43,113.3 1,018.4 40,967.4 844.3 45,056.4

2028 1,123.2 42,187.5 1,021.3 42,805.8 195.6 42,878.9 180.4 43,457.1 1,081.6 41,197.3 899.0 45,422.9

2029 1,300.8 42,734.2 1,182.9 43,405.7 239.2 43,536.1 218.3 44,161.8 1,245.4 41,800.7 1,047.2 46,099.7

2030 1,463.5 43,383.3 1,326.4 44,039.6 282.7 44,299.5 257.6 44,900.6 1,385.6 42,355.1 1,187.9 46,639.8
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Appendix B. Distributed Wind Capital Costs

Table B-1. Distributed Wind Capital Costs by Cost Scenario for the Baseline Scenario ($/kW)

Year\kW 2.5 5 10 20 50 100 250 500 750 1,000 1,500+

2018 8,117.55 6,683.15 5,669.30 4,952.46 3,884.77 3,594.93 2,956.80 2,673.65 2,508.49 1,653.26 1,533.51

2019 7,582.54 6,239.44 5,290.11 4,618.89 3,567.83 3,300.06 2,714.91 2,452.94 2,300.12 1,636.10 1,517.47

2020 7,003.92 5,759.54 4,879.99 4,258.12 3,231.14 2,986.85 2,456.95 2,217.62 2,078.00 1,619.54 1,502.03

2021 6,585.66 5,412.68 4,583.60 3,997.41 2,976.41 2,749.96 2,262.24 2,040.07 1,910.47 1,603.59 1,487.19

2022 6,127.92 5,033.07 4,259.22 3,712.07 2,709.44 2,501.70 2,057.29 1,853.22 1,734.18 1,588.25 1,472.96

2023 5,629.69 4,619.88 3,906.12 3,401.46 2,432.34 2,244.03 1,843.72 1,658.52 1,573.55 1,573.55 1,459.34

2024 5,091.51 4,173.53 3,524.69 3,065.92 2,147.09 1,978.79 1,623.07 1,559.47 1,559.47 1,559.47 1,446.31

2025 4,515.23 3,695.58 3,116.23 2,706.60 1,855.50 1,707.65 1,546.04 1,546.04 1,546.04 1,546.04 1,433.90

2026 4,323.56 3,536.71 2,980.54 2,587.31 1,742.22 1,602.45 1,533.26 1,533.26 1,533.26 1,533.26 1,422.08

2027 4,113.58 3,362.65 2,831.87 2,456.59 1,626.19 1,521.12 1,521.12 1,521.12 1,521.12 1,521.12 1,410.87

2028 3,886.86 3,174.69 2,671.32 2,315.42 1,509.63 1,509.63 1,509.63 1,509.63 1,509.63 1,509.63 1,400.27

2029 3,645.19 2,974.34 2,500.18 2,164.92 1,498.80 1,498.80 1,498.80 1,498.80 1,498.80 1,498.80 1,390.26

2030 3,390.50 2,763.19 2,319.79 2,006.29 1,488.62 1,488.62 1,488.62 1,488.62 1,488.62 1,488.62 1,380.87
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Table B-2. Distributed Wind Capital Costs by Cost Scenario for the High Scenario ($/kW)

Year\kW 2.5 5 10 20 50 100 250 500 750 1,000 1,500+

2018 10,792.17 8,893.03 7,550.68 6,601.58 5,387.50 4,988.86 4,111.20 3,721.77 3,494.61 2,020.47 1,874.12

2019 10,458.58 8,616.45 7,314.39 6,393.77 5,147.79 4,765.86 3,930.93 3,557.31 3,339.36 2,003.06 1,857.85

2020 10,125.00 8,339.87 7,078.10 6,185.97 4,908.08 4,542.86 3,750.65 3,392.84 3,184.11 1,985.65 1,841.58

2021 9,854.09 8,115.27 6,886.25 6,017.28 4,715.77 4,363.97 3,605.93 3,260.82 3,059.51 1,977.24 1,833.74

2022 9,583.17 7,890.68 6,694.40 5,848.58 4,523.45 4,185.07 3,461.20 3,128.80 2,934.90 1,968.82 1,825.91

2023 9,266.92 7,628.48 6,470.40 5,651.60 4,325.09 4,000.55 3,310.27 2,991.12 2,804.94 1,965.61 1,822.95

2024 8,950.66 7,366.28 6,246.41 5,454.61 4,126.72 3,816.02 3,159.34 2,853.43 2,674.98 1,962.39 1,820.00

2025 8,810.44 7,250.11 6,147.25 5,367.47 4,026.68 3,723.00 3,084.21 2,784.94 2,610.37 1,961.67 1,819.38

2026 8,670.21 7,133.95 6,048.09 5,280.34 3,926.65 3,629.98 3,009.09 2,716.45 2,545.75 1,960.94 1,818.75

2027 8,413.85 6,921.44 5,866.57 5,120.73 3,782.44 3,495.85 2,898.25 2,615.37 2,450.36 1,960.92 1,818.80

2028 8,157.50 6,708.93 5,685.05 4,961.12 3,638.23 3,361.72 2,787.41 2,514.28 2,354.96 1,960.91 1,818.85

2029 8,040.43 6,611.97 5,602.31 4,888.43 3,567.82 3,296.26 2,733.79 2,465.42 2,308.88 1,960.57 1,818.59

2030 7,923.36 6,515.01 5,519.57 4,815.75 3,497.40 3,230.81 2,680.17 2,416.56 2,262.79 1,960.23 1,818.34
37

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Appendix C. Economic Potential Results

Table C-1. Economic Potential Results by Turbine Class of Capital Cost Sensitivity Analysis in 2020 (MW)

CAPEX ($/W)/Turbine Class Residential

(2–20kW)

Commercial

(21–100kW)

Midsize

(101–999kW)

Large

(>=1,000kW)

Total

0 4,264.4 3,975.6 2,301.6 1,955.9 12,497.5

1 2,562.4 2,606.7 1,660.3 1,546.8 8,376.2

2 1,157.8 1,260.4 937.5 1,069.9 4,425.6

3 397.2 424.6 655.3 1,069.9 2,547.1

4 125.4 380.1 655.3 1,069.9 2,230.7

5 40.2 380.1 655.3 1,069.9 2,145.4

6 21.2 380.1 655.3 1,069.9 2,126.5

7 20.0 380.1 655.3 1,069.9 2,125.2

Table C-2. Economic Potential Results by Turbine Class of Capital Cost Sensitivity Analysis in 2030 (MW)

CAPEX ($/W)/Turbine Class Residential

(2–20kW)

Commercial

(21–100kW)

Midsize

(101–999kW)

Large

(>=1,000kW)

Total

0 2,234.3 1,648.9 1,131.8 366.0 5,381.0

1 1,304.7 775.9 495.4 152.2 2,728.2

2 685.2 509.8 266.0 101.9 1,563.0

3 470.4 509.8 266.0 101.9 1,348.1

4 448.6 509.8 266.0 101.9 1,326.4

5 448.6 509.8 266.0 101.9 1,326.4
38

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Appendix D. Value of Generation

Table D-1. Value ($) of 10,000 kWh of Generation by Technology by Yeara

County Balancing 

Authority

2020 2025 2030

Wind Solar Wind Solar Wind Solar

Santa Barbara CIPV 298 327 350 339 348 325

Santa Clara CIPV 309 783 349 848 354 776

Inyo CISC 304 318 347 342 348 321

Yolo CIPV 289 185 331 200 331 174

Merced CIPV 290 300 335 299 337 274

Alameda CIPV 298 330 343 357 348 326

Napa CIPV 295 481 333 461 337 389

Santa Cruz CIPV 302 673 344 728 348 667

Imperial IID 296 304 329 328 325 302

Shasta CIPV 281 397 329 402 327 368

Calaveras CIPV 294 541 331 566 330 534

Del Norte CIPV 296 624 338 486 334 403

Mono CISC 319 369 360 417 357 376

Placer CIPV 294 371 338 386 334 353

San Diego CISD 324 505 367 539 363 506

Yuba CIPV 289 348 330 359 326 345

Siskiyou CIPV 299 710 348 845 346 685

San Luis Obispo CIPV 299 394 343 404 344 376

San Mateo CIPV 297 244 346 263 350 241

Marin CIPV 296 262 341 249 346 228

Modoc CIPV 301 447 355 502 356 456

Kings CIPV 265 398 304 439 306 402

Lake CIPV 282 737 320 559 326 806

Mendocino CIPV 291 357 333 378 333 352

Monterey CIPV 301 250 347 274 353 248

San Joaquin CIPV 290 200 332 225 335 206

Riverside CISC 306 282 348 288 347 272

Colusa CIPV 289 226 326 249 324 227

Sacramento BANC 308 244 347 255 344 208

Butte CIPV 286 280 326 331 326 283

Fresno CIPV 276 402 319 441 317 408
39

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

County Balancing 

Authority

2020 2025 2030

Wind Solar Wind Solar Wind Solar

Tulare CISC 292 786 335 835 335 790

Tehama CIPV 292 262 338 278 337 254

Nevada CIPV 282 484 323 485 320 444

Madera CIPV 281 513 325 560 325 522

Plumas CIPV 298 986 346 991 347 887

San Benito CIPV 309 538 349 581 355 532

Solano CIPB 285 126 327 140 331 128

Sonoma CIPV 295 328 338 377 342 324

Stanislaus CIPV 294 277 340 297 343 272

Contra Costa CIPB 291 297 334 319 340 292

Sutter CIPV 299 222 343 240 342 219

Trinity CIPV 277 1,716 317 1,953 314 1,775

Humboldt CIPV 291 489 334 556 332 444

El Dorado CIPV 296 554 335 581 331 553

Alpine CIPV 304 543 341 586 340 537

Amador CIPV 301 477 344 519 336 454

Glenn CIPV 297 243 336 261 333 238

Kern CISC 311 311 356 335 357 309

Lassen CIPV 300 530 347 588 352 540

Los Angeles LDWP 313 269 317 280 311 280

Orange CISC 330 407 372 439 371 412

San Bernardino CISC 308 263 347 268 346 251

San Francisco CIPV 296 137 342 148 348 136

Mariposa CIPV 287 840 326 959 327 906

Tuolumne CIPV 289 552 329 622 325 698

Ventura CISC 305 269 346 297 344 272

Sierra CIPV 292 806 337 694 339 615

a These values were used to create Figure 15

BANC = Balancing Authority of Northern California, CIPB = Pacific Gas & Electric Bay Area Balancing 

Authority, CIPV = Pacific Gas & Electric Valley Area Balancing Authority, CISC = Southern California 

Edison Balancing Authority, LDWP = Los Angeles Department of Water & Power, IID = Imperial Irrigation 

District
40

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Appendix E. Change in Value of Generation

Table E-1. Change in Value (%) of 10,000 kWh of Generation by Technology by Yeara

County Balancing 

Authority

2025 2030

Wind 

Percentage 

Change

Solar 

Percentage 

Change

Wind 

Percentage

Change

Solar 

Percentage

Change

Santa Barbara CIPV 117 104 117 99

Santa Clara CIPV 113 108 115 99

Inyo CISC 114 108 114 101

Yolo CIPV 115 108 115 94

Merced CIPV 116 100 116 91

Alameda CIPV 115 108 117 99

Napa CIPV 113 96 114 81

Santa Cruz CIPV 114 108 115 99

Imperial IID 111 108 110 99

Shasta CIPV 117 101 116 93

Calaveras CIPV 112 105 112 99

Del Norte CIPV 114 78 113 65

Mono CISC 113 113 112 102

Placer CIPV 115 104 114 95

San Diego CISD 113 107 112 100

Yuba CIPV 114 103 113 99

Siskiyou CIPV 116 119 116 97

San Luis Obispo CIPV 115 103 115 95

San Mateo CIPV 116 108 118 99

Marin CIPV 115 95 117 87

Modoc CIPV 118 112 118 102

Kings CIPV 115 110 115 101

Lake CIPV 114 76 115 109

Mendocino CIPV 115 106 115 99

Monterey CIPV 115 109 117 99

San Joaquin CIPV 115 112 116 103

Riverside CISC 114 102 114 96

Colusa CIPV 113 110 112 101

Sacramento BANC 113 105 112 85

Butte CIPV 114 118 114 101
41

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

County Balancing 

Authority

2025 2030

Wind 

Percentage 

Change

Solar 

Percentage 

Change

Wind 

Percentage

Change

Solar 

Percentage

Change

Fresno CIPV 116 110 115 102

Tulare CISC 115 106 115 101

Tehama CIPV 115 106 115 97

Nevada CIPV 114 100 114 92

Madera CIPV 116 109 116 102

Plumas CIPV 116 101 116 90

San Benito CIPV 113 108 115 99

Solano CIPB 115 111 116 101

Sonoma CIPV 114 115 116 99

Stanislaus CIPV 116 107 117 98

Contra Costa CIPB 115 107 117 98

Sutter CIPV 115 108 114 99

Trinity CIPV 114 114 113 103

Humboldt CIPV 115 114 114 91

El Dorado CIPV 113 105 112 100

Alpine CIPV 112 108 112 99

Amador CIPV 114 109 112 95

Glenn CIPV 113 107 112 98

Kern CISC 114 108 115 99

Lassen CIPV 116 111 117 102

Los Angeles LDWP 101 104 99 104

Orange CISC 113 108 112 101

San Bernardino CISC 113 102 112 96

San Francisco CIPV 115 109 117 99

Mariposa CIPV 113 114 114 108

Tuolumne CIPV 114 113 113 126

Ventura CISC 114 110 113 101

Sierra CIPV 115 86 116 76

a These values were used to create Figure 16.

BANC = Balancing Authority of Northern California, CIPB = Pacific Gas & Electric Bay Area Balancing 

Authority, CIPV = Pacific Gas & Electric Valley Area Balancing Authority, CISC = Southern California 

Edison Balancing Authority, LDWP = Los Angeles Department of Water & Power, IID = Imperial Irrigation 

District