GRI-97/0298



# Topical Report 

# I Hearth Products Meter Study 

# (1995-1997)

Prepared by: ]. Menkedick 

### P. Hartford S. Collins S. Shumaker D. Wells Battelle



### Gas Research Institute Appliances and Water Heating September 1997

### GRI-97/0298


# HEARTH PRODUCTS METER STUDY (1995

- 1997)
TOPICAL REPORT
Prepared by:


### John Menkedick, Pam Hartford, Shawna Collins, Shawn Shumaker, and Darlene Wells
Battelle 505 King Avenue 

### Columbus, Ohio 43201 

### For 

### Gas Appliance Technology Center Gas Research Institute 8600 West Bryn Mawr Avenue Chicago, Illinois 60631 

### Program Team Leader Rodney Rinholm Appliances and Water Heating 

# September 1997LEGAL NOTICE
This report was prepared by Battelle as an account ofwork sponsored by the Gas Research Institute (GR!). Neither GR!, members ofGR!, Battelle, officers, trustees, or staffof Battelle, nor any person acting onbehalfofeither:
a. Makes any warranty orrepresentation, expressed or implied, with respect to the accuracy, completeness, orusefulness ofthe information contained inthis report, orthat the use ofany information, apparatus, software, method, orprocess disclosed in this report may not infringe privately owned rights; or b. Assumes any liability with respect to the use of, or for damages resulting from the use of, any information, apparatus, software, method, orprocess disclosed in this report. Reference to trade names or specific commercial products, commodities, or services in this report does not represent nor constitute an endorsement, recommendation, or favoring by GR! or Battelle ofthe specific commercialproduct, commodity, or service.

TopicalReport-September, 1997 ii Hearth Products Meter Study50272-101 REPORT DOCUMENTATION 1. REPORT NO. 2. 3. Recipient's Accession No. PAGE 4. Title and Subtitle 5. Report Date Hearth Products Meter Study (1995-1997) September 1997 6. 7. Author(s) 8. Performing Organization Rept. No. Menkedick, J.R., Hartford, P.A., Collins, S.L., Shumaker, S.M., Wells, D.E. 9. Performing Organization Name and Address 10. Project/Task/Work Unit No. Battelle Memorial Institute 505 King Avenue 11. Contract(C) or Grant(G) No. Columbus, Ohio 43201-2693 (C) 5092-281-2494 (G) 12. Sponsoring Organization Name and Address 13. Type of Report & Period Covered Gas Research Institute Topical 8600 West Bryn Mawr Avenue Chicago, IL 60631 14. December 1995 - May 1997
15. Supplementary Notes 16. Abstract (Limit 200 words) The Hearth Products Meter Study is a multi-year study in which cooperating utilities identify, access, and submeter individual hearth products (and furnaces in most cases) in residences in their service area in order to understand how gas hearth products are being used in the field, what factors affect this usage, and the impact on gas load throughout the year for different gas hearth products. The report presents data summaries and statistical analysis on final results to predict average gas loads and usage patterns as a function of the type of equipment, geographical location, season, household type, household demographics, and other parameters deemed important. Statistical models were used to assess the effect of multiple factors simultaneously and reduce the possibility of misleading results due to the confounding of effects. The results will be used to address a wide range of questions facing utilities including strategic marketing, load forecasting, resource planning, and billing estimation. In addition to meeting utilities' needs for load data, the data may also be used to ensure that hearth products are treated in a reasonable and fair way by local, state, and federal regulators with regard to interests of gas consumers and the gas industry.
17. Document Analysis
a. Descriptors Gas usage, energy usage, load profiles, hearth products, furnaces, load research b. Identifiers, open-ended terms Energy, end-use, metering c. COSATI Field/Group 18. Availability Statement Availability Unlimited
(See ANSI-Z39.18)
Topical Report

- September, 1997 19. Security Class (This Report) Unclassified 20. Security Class (This Page) Unclassified

iii 21. No. of Pages
22. Price 44

OPTIONAL FORM 272 (4-77) (Formerly NTIS-35) Department of Commerce Hearth Products Meter StudyThispage left intentionally blank

Topical Report

- September, J 997 iv Hearth Products Meter Study

### Title: Contractor: Principal Investigators: Report Period: Objective:
Technical Objective:

Results: RESEARCH SUMMARY
Hearth Products Meter Study (1995-1997) Battelle, 505 King Avenue, Columbus, Ohio 43215 John Menkedick and PamHartford Topical Report, Results from December 1995 to May 1997
To characterize gas usage and factors that influence the usage for a variety of gas hearth products in different regions ofthe United States and Canada. Gas hearth products are the fastest growing gas appliance sector with growth rates projected to bebetween 10 and 30 percentperyear, depending onthe type ofproduct. To help the gas industry make strategic decisions concerning this tremendous growth, it is necessary to knowhow gas hearth products are being used in the field, what factors affect this usage, and the impact on gas load throughoutthe year for different gas hearth products. Therefore GRI has begun the Hearth Products Meter Study, a submeteringprogram for gas hearth products coordinated with local distributing companies (LDCs) across the U.S. and Canada. The Hearth Products Meter Study is a multi-year study in which cooperating utilities identify, access, and submeter individual hearth products (and furnaces in most cases) inresidences in their service area. GRIlBattelle will conduct data summaries and statistical analysis on final results to predict average gas loads and usage patterns as a function ofthe type ofequipment, geographical location, season, household type, household demographics, and any other parameters deemed important. The purpose of this topical report is to provide preliminary results based on data available through May 31, 1997. Demographic, equipment and other questionnaire information collected from participating households is summarized in the report. Average heating season. hearthproduct usage ranged from 105 CCF for 34 fireplaces to 171 CCF for 6 fireplace inserts. Decorative gas logs, withthe largest number ofsamples in the study, had an average of 120 CCF for the heating season. Estimated hourly pilotusage ranged from 0.35 CF to 2.83 CF. The hearth product load profile is flatter than the furnace, butpreliminary assessment suggests that hearth productusage does increase during peakperiods ofextremely cold weather. The amount ofusage, pattern ofusage, correlation with degree days, and interaction withthe furnace all varied significantly across different customers. Factors most significantly related to hearth product usage include degree day measures, presence ofa pilot light, hearth producttype, andtype of Topical Report

- September. 1997 v Hearth Products Meter StudyTechnical Approach:

Project Implications: day. On average, based onthe data analyzed to date, 67% ofthe hearth product usage can be characterized as incremental load for the household. Data analysis began with validation ofthe data and handling ofmissing values. This was followed by descriptive statistics and summaries. Statistical models were used to assess the effect ofmultiple factors simultaneously and reduce the possibility ofmisleading results due to the confounding ofeffects. The relationship betweenhearth product usage and the possible predictors was assumed to be linear and have the following form: Hearth Product Usage 

## =

## Po + pj*Predictor j

### +error, where i 

## = 1to the number ofpredictors and 

### error is random noise assumed to be normally distributed, with mean zero and variance 0 2 independent ofthe predictors. A few variables were considered ofprimaryinterest and were included 

### in all models, regardless ofthe usage period (heating season, season, month, or day). These included degree day measures, hearth producttype, and the presence ofa pilot light. The steps inthe variable selection/reduction process for other candidate variables included an assessment ofstatistical correlations, combination ofvariables, stepwise regression, R2 analysis, and professionaljudgement. A similar modeling approach was usedto assess the impact ofhearthproductusage on furnace usage inthe winter months. The results will beused to address a wide range ofquestions facing utilities including strategic marketing, load forecasting, resource planning, and billing estimation. In addition to meeting utilities' needs for load data, the data may also be used to ensure that hearthproducts are treated in a reasonable and fair way by local, state, and federal regulators with regard to interests ofgas consumers and the gas industry. GRI ProjectManager Rodney Rinholm Program Team Leader Appliances and Water Heating

Topical Report- September, 1997 vi Hearth Products MeterStudy

### TABLE OF CONTENTS**~** 

### EXECUTIVE SUMMARY
... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. x 

### INTRODUCTION
............................................................. 1 SECTION 1 STUDY OBJECTNES, DESIGN, AND CURRENT STATUS
.............. 2 1.1 OBJECTIVES
................................................2 1.2 STUDY DESIGN AND CURRENT STATUS
....................... 3 SECTION 2 DATA BASE DESCRIPTION
....................................... 7 2.1 WEATHER DATA
............................................ 7 2.2 DEMOGRAPHIC AND EQUIPMENT INFORMATION
.............. 7 2.3 GAS USAGE DATA
.......................................... 7 SECTION 3 STATISTICAL ANALYSIS ISSUES, DEFINITIONS, AND APPROACH
.... 9 3.1 DATA ISSUES
............................................... 9 3.2 MISSING DATA
............................................ 10 3.3 APPROACH TO DATA ANALYSIS
............................ 12 3.4 BOXPLOTS
................................................ 12 3.5 HISTOGRAMS
............................................. 13 3.6 DEFINITION OF SEASONS
................................... 14 3.7 SIGNIFICANT DIGITS
....................................... 14 SECTION 4 DESCRIPTIVE STATISTICS AND SUMMARIES
...................... 15 4.1 QUESTIONNAIRE SUMMARIES
.............................. 15 4.2 HEARTH PRODUCT AND FURNACE GAS USAGE SUMMARIES
.. 22 4.2.1 Heating Season Gas Usage
................................ 

### 22 4.2.2 Monthly Gas Usage
......................................

### 24 4.2.3 Daily Gas Usage
......................................... 

### 26 4.2.4 Hourly Gas Usage
....................................... 

### 26 4.2.5 Pilot Usage
............................................. 

### 29 4.3 PEAK DAY AND PEAK HOUR USAGE
......................... 30 SECTION 5 CHARACTERIZATION OF SUBSETS OF CUSTOMERS
............... 35 SECTION 6 RESULTS

- FACTORS RELATED TO HEARTH PRODUCT USAGE
..... 38 6.1 DESCRIPTION OF AVAILABLE DATA
........................ 38 6.2 STATISTICAL METHODOLOGY
.............................. 39 6.3 MODELING ANALYSIS RESULTS
............................ 39 SECTION 7 MODELS TO ASSESS THE HEARTH PRODUCT-FURNACE INTERACTION
..................................................40 7.1 RESULTS OF MODELING THE INTERACTION
.................. 41 TopicalReport

- September, 1997 vii Hearth Products Meter StudyTable 1.1 Table 4.1 Table 4.2

Figure ES.l Figure ES.2 Figure ES.3 Figure 1.1 Figure 3.1 Figure 3.2 Figure 4.1 Figure 4.2 Figure 4.3 Figure 4.4 Figure 4.5 Figure 4.6 Figure 4.7 Figure 4.8 Figure 4.9 Figure 4.10 Figure 4.11 Figure 4.12 

### TABLE OF CONTENTS (Continued)

7.2 FACTORS RELATED TO THE INTERACTION BETWEEN HEARTH PRODUCT AND FURNACE
..........................44


### LIST OF TABLES Number ofHearth Products Metered Through May 31, 1997.
. ................ 6 Summary ofSelected Household and Demographic Characteristics.
........... 17 Summary ofSelected Household and Furnace Equipment Characteristics, by Hearth Product.
.................................................. 20


### LIST OFFIGURES Average Gas Usage (CCF) for the Heating Season (September- May), by Hearth Product Type.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi Average Daily Hearth Product and Furnace Gas Usage as a Percent ofthe Maximum Daily Usage
............................................. xii Estimated Daily Hearth Product Gas Usage (CCF) for Each Season
.......... xiv DOE Heating Regions
............................................... 5 Diagram ofa Box Plot.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Diagram ofa Histogram
............................................. 13 Summary ofSelected Demographic Characteristics.
. ...................... 16 Distribution ofthe Age ofthe Hearth Product, by Type ofHearth Product.
..... 17 Percentage ofHearth Products Reported to Have a Pilot, byType ofHearth Product.
.......................................................... 18 Type ofTemperature Control, Overall and for Each Type ofHearth Product.
... 19 Reason for Purchasing the Hearth Product (N=80)
......................... 21 Primary Reason Hearth Product is Typically Used (N=79).
. ................ 21 Heating Season (September, 1996

- May, 1997) Hearth Product Gas Usage, by Type ofHearth Product

- Histogram.
. .............................. 23 Heating Season (September, 1996

- May, 1997) Hearth Product Gas Usage, by Type ofHearth Product

- Box Plot.
................................ 24 Average Monthly Hearth Product Gas Usage, Overall and by Type ofHearth Product
............................. '"
.......................... 25 Average Daily Hearth Product and Furnace Gas Usage as a Percent ofthe Maximum Daily Usage by Type ofHearth Product.
....................... 27 Furnace, Hearth Product, and Total Furnace and Hearth Product Average Hourly Gas Usage byType ofHearth Product for January, 1997
.............. 28 Distribution ofthe Estimated Hearth Product Hourly Pilot Gas Usage by Type ofHearth Product

- Histogram.
. ................................ 29 Topical Report

- September, 1997 viii Hearth Products Meter StudyFigure 4.13 Figure 4.14 Figure 4.15 Figure 4.16 Figure 5.1 Figure 5.2 Figure 5.3 Figure 5.4 Figure 7.1 Figure 7.2 Figure 7.3 Figure 7.4 TABLE OF CONTENTS (Continued)

Distribution ofthe Estimated Hearth Product Hourly Pilot Gas Usage by Type ofHearth Product

- Box Plot.
.................................. 30 Ratio ofthe Peak Weather Day Gas Usage to the Average Daily Gas Usage During the Heating Season for the Gas Furnace and Each Hearth Product Type
............................................................ 32 Ratio ofthe Gas Usage ofthe Five Coldest Days to the Gas Usage onthe Top Forty-Five Coldest Days for the Gas Furnace and Each Hearth Product.
.... 33 Comparison ofthe Average Hourly Furnace and Hearth Product PeakDay Gas Usage to the Average Hourly Furnace and Hearth Product Gas Usage during January, 1997, by Type ofHearth Product.
......................... 34 Example ofa Customer With Very Heavy Hearth Product Usage that May Serve as a Supplemental Heat Source
................................... 35 Example ofa Customer with Moderate Hearth Product Usage Significantly Related to Weather
................................................. 36 Example ofa Customer With Regular Hearth Product Usage Independent of Weather.
. ....................................................... 36 Example ofa CustomerWith Only Sporadic Hearth Product Usage.
. ......... 37 Usage Data from a Household with SignificantInteraction Between Hearth Product Gas Usage and Furnace Gas Usage
..............................42 Furnace Usage Adjusted for Weather Plotted Against Hearth Product Usage Adjusted for Weather for a Household With SignificantInteraction
........... 42 Usage Datafrom a Household with Little Interaction BetweenHearth Product Gas Usage and Furnace Gas Usage
..............................43 Furnace Usage Adjusted for Weather Plotted Against Hearth Product Usage Adjusted for Weather for a Household with Little Interaction
...........43

Topical Report

- September, 1997 ix Hearth Products Meter Study

## EXECUTIVE SUMMARY
To help the gas industry develop strategic plans for managing growth, Gas Research Institute (GRI) is conducting a multi-year sub-metering study to evaluate gas hearth product use. The study is being conducted for GRI by Battelle and cooperating local distribution companies (LDC's) throughout the United States and Canada. The overall aim ofthe study is to characterize gas use and the factors affecting that use for a variety ofgas hearth products. The results will be used to address a wide range ofquestions facing utilities including load forecasting, resource planning, and strategic marketing. 

### Inaddition, the results will be used to ensure that local, state, and federal regulations meet the interests ofconsumers and the gas industry. As ofMay 1997, 118 households from eight LDCs were collecting usage data hourly. Usage data is being collected on gas fireplaces, decorative gas logs, vent-free gas logs, fireplace inserts, and gas stoves. Geographically, most ofthe participants are located inDOE heating zones IV and V, representing average heating load hours between 2,000 and 3,000 hours. 

### Itmustbe emphasizedthat results in this reportare basedon only a subsetof the data already collected. The study has been extended for a third year to run through the 1997-1998 heating season and additional utilities are expected tojointhe study for the upcoming heating season. As data that were not available for this report is added and the additional data is collected during the 1997-1998 heating season, results may change somewhat and comparisons and conclusions may become more clear. Although the data contains a wealth ofinformation to address study objectives, there are three primary cautions that should be kept in mind when interpreting and drawing conclusions from the data: 1. Households entered the study at different times. Therefore different time periods contain differing numbers ofavailable households, as well as different households. Because ofthis, some analyses were limited to only those households with data for the entire time period ofinterest (for example, for an entire heating season). 2. Sample sizes are unequal and in some cases small. Forexample, while for this report there were data available for 49 decorative gas logs, there were only data for seven fireplace inserts, and four gas stoves. Therefore sample size should always be taken into account when assessing the strength ofconclusions that can be drawn from the data. 3. Nineteen households had two hearth products monitored in the home. Unless otherwise noted, the summaries presented include the total usage by the two hearth products. These homes were not included in the modeling analyses for this report. It is anticipated that they will be included in analyses inthe final report. Topical Report

- September, 1997 x Hearth Products Meter StudyForhouseholds included in this report, the majority ofhomes are two-story orranch suburban homes, 17 years old on average, and averaging 2,378 square feet and 7 rooms. The average age ofthe adults inthe home is 43 years, with an average of 1 childper home. Eightytwo percent ofthe households had an annual income greater than $50,000. The majority ofthe hearth products were less than 5 years old. Twenty percent ofthe decorative logs had pilot lights while more than 50% ofthe otherhearth products types were reported to have a pilot. Only six percent ofthe hearth products were thermostatically controlled with the remainder controlled by either an On and Off, or a Low-Medium-High temperature control. The most frequent reason for purchasing the hearth product was "Appearance." "Looks and Heat" are cited as the primary reason for using the hearth product. As illustrated inFigure ES.l, the average heating season hearth product usage for the data summarized in this report ranged from 105 CCF for the 34 flreplaces to 171 CCF for the 6 flreplace inserts. Decorative gas logs, with the largest number ofsamples inthe study, had an average of 120 CCF for the heating season. Individual household hearth product heating season usage ranged from 0 CCF to 824 CCF with 75% ofthe population using less than 300 CCF for the heating season. Load proflles indicate that overall and within eachtype ofhearth product, the hearth product usage is less related to weather than the gas furnace usage with a resulting flatter load proflle as illustrated in Figure ES.2.
180 G:"160 0 0 

# - Q) 140 C) ns en ::J 120 en ns C) 

## g 100 I--- en ns Q) 80 

### en - C) c :t:J 60 ns - Q) l: Q) 40 C) - 

### l! Q)

### ~ 20 - 0 Decoratiw Gas Log (0=38) Fireplace (0=34) Fireplace nsert (0= 6) Gas Stow (0= 3) 

### Figure ES.l Average Gas Usage (CCF) for the Heating Season (SeptemberMay), by HearthProductType.

Topical Report-September, 1997 xi Hearth Products MeterStudyOverall**---------------------r============~ ~**  1 - Furnace

e---e---e Hearth Product**~**

20

o

# ~~~~~~~~~~~ 09101196 10101196 11101196 12101196 01101197 02101197 03101197 04101197 05101197 06101197 Date 

### 8

Figure ES.2 Average Daily Hearth Product and Furnace Gas Usage as a Percent of the Maximum Daily Usage.
Although the hearth product load profile maybe flatter than the furnace, preliminary assessment suggests that hearth product usage does increase during peakperiods ofextremely cold weather. On average, hearth product usage is highest from 6:00 p.m. to 11 :00 p.m., and higher onweekends, holidays, and peak days. The hearthproducts' evening peaks add to the evening heating load, but do not change the peakhour within a day, though on extremely cold days there is an indication the hearth product usage could shift the daily heating load peak from the mornings to the evening hours. The estimated hourly pilotusage ranged from 0.35 CF to 2.83 CF. Initial examination ofplots ofhearth product usage for different customers indicated widely varying patterns ofusage. The amount ofusage, pattern ofusage, correlation with degree days, and interaction withthe furnace all varied significantly across different customers. Subsets ofcustomers were identified accordingto three different usage characteristics: total hearth productusage, usage inthe shoulder season, and net increase intotal household heating load in the winter. Classification ofcustomers into a HIGH group for each ofthe three usage characteristics (based on being inthe top 20% ofusage for the particular characteristic) revealed strong correlationbetween the users in the HIGH group for each usage characteristic, indicating that those users who have the highest total hearth product usage also often use the hearth product heavily inthe shoulder seasons and are also estimated to generate the greatest net increase intotal household heating load inthe winter.
Topical Report

- September. 1997 xii Hearth Products Meter StudyStatistical modeling analyses indicated that the factors most significantly related to hearth product usage include:
• Degree day measures • Presence ofa pilot light • Hearth product type • Type ofday

- weekend orweekday

- holiday

- peak day. A modeling approach was used to assess the impact ofhearth product usage on furnace usage inthe winter months. The following linear regression model was used: Daily Furnace Usage = 

## Po +

## PI x Daily Degree Days 

### +

## P2 X Daily Hearth Product Usage 

### Inthis model, the parameter

## P2 (the slope parameterfor Daily Hearth Product Usage) represents the decrease orincrease in furnace usage (in CCFs) for each CCF ofhearth product usage, after adjusting both variables for the effect ofweather. The average estimated slope for the 72 households included inthe analysis was -0.33, representing a decrease of0.33 CCF in furnace usage for every CCF ofhearth product usage. Thus, on average, based onthe data analyzed to date, 67% ofthe hearth product usage can be characterized as incremental load for the household. Over 70% ofthe slope estimates were negative indicating that mosthomes did decrease furnace usage as a result ofhearth product usage. Itis important to note that results based onthe current data included in this report are heavily influenced by homes with decorative gas logs and fireplaces whichrepresent the majority ofhomes summarized in this report. Figure ES-3 presents a characterization ofthe average daily load throughout the year for a service areawiththe following characteristics:
• weather that averages, perday, 13 degree days inthe shoulder seasons (September, October, November, March, April, May), 27 degree days in winter (December, January, February), and 49 degree days onthe top 5 peak weather days;
• a distribution ofhearth products that includes 46% decorative logs, 44% fireplaces, 7% fireplace inserts, and 4% gas stoves; and
• a distribution ofhearth products inwhich 49% ofthe products had standingpilots. Figure ES.3 was estimated using statistical models which related hearth productusage to degree day measures, hearth producttype, presence ofa pilot light, and type ofday. 

### Inthe figure, the height ofthe block for each seasonal period (summer, shoulder, winter, and peak) corresponds to the estimated average daily hearth product usage inthat period. The heightofthe shaded portion ofthe block corresponds to the estimated average net increase intotal household heating load resulting from use ofthe hearth product (estimated at 67% ofaverage hearth productusage as discussed in Section 7.1). Topical Report

- September, 1997 xiii Hearth Products Meter Study

### u::- U**~** 

# i :::> gj (!) 1:) ::I 

# £**~** CD ::J:

### ~ 0 CD**~** 

# ! 1.35

1.20
tc15

0.90

0.75

0.60

0.45

0.30

0.15 Net Increase in Total Household Heating Load

Summer Shoulder Days of Use Winter


### Figure ES.3 Estimated Daily Hearth Product Gas Usage (CCF) for Each Season.

Topical Report

- September, J 997 xiv Hearth Products Meter Study

## INTRODUCTION
Gas hearth products are the fastest growing gas appliance sector with growth rates projected to be between 10 and 30 percentper year, depending onthe type ofproduct. To help the gas industry make strategic decisions concerning this tremendous growth, it is necessary to knowhow gas hearth products are being used in the field, what factors affect this usage, and the impact on gas load throughout the year for different gas hearth products. Therefore GR! has begun the Hearth Products Meter Study, a submetering program for gas hearth products coordinated withlocal distributing companies (LDCs) across the U.S. and Canada. The Hearth Products Meter Study is a multi-year study in which cooperating utilities identify, access, and submeter individual hearth products (and furnaces in most cases) in residences intheir service area. GRIlBattelle has designed the study andquestionnaires, coordinated the activities ofall utilities, assisted in gathering the raw data once meters have been installed, andperformed data reduction analyses within and across service areas. GRIlBattelle will conduct data summaries and statistical analysis on final results to predict average gas loads and usage patterns as a function ofthe type ofequipment, geographical location, season, household type, household demographics, and any other parameters deemed important. The purpose ofthis report is to provide preliminary results based on data available through May 31, 1997. 

### Itmustbe emphasizedthat results in this reportare basedon onlya subsetof the data already collected. The study has been extended for a third year to run through the 1997-1998 heating season and additional utilities are expected tojointhe study for the upcoming heating season. As data that were not available for this report is added and the additional datais collected during the 1997-1998 heating season, results may change somewhat and comparisons and conclusions may become more clear.

Topical Report-September, 1997 1 Hearth Products Meter Study

## SECTION 1 STUDY OBJECTIVES, DESIGN, AND CURRENT STATUS

1.1 OBJECTIVES The overall objective ofthe Hearth Products Meter Study is to characterize gas usage and factors that influence the usage for a variety ofgas hearth products in different regions ofthe United States and Canada. 

### Inparticular the study has the following specific study objectives: OBJECTIVE 1. 

### Estimate annual, monthly, and daily gas usage for different hearth product types as it is related to geographic regions, housing types, and other explanatoryfactors. OBJECTIVE 2. 

### Identify factors that affect hearth products' gas usage. Construct and evaluate statistical models to predict gas usage based on significant explanatory factors. These factors may include:


### • weatherinformation such as hourly temperatures, degree days, or effective degree days;


### • equipment characteristics such as manufacturer, inputbtu and efficiency rating, type ofheat recovery, ignition system and controls, thermostat, and vent system; 

### • building characteristics such as housing type (multi-family versus single family), house size, construction, and age, whether the equipment replaces an existing fireplace oris a new installation, and the location within the house ofthe hearthproduct, as well as the equipment mix of gas and electric appliances inthe house;


### • demographic information such as age, income, number ofresidents, and lifestyle characteristics. OBJECTIVE 3. 

### Characterize the pattern ofusage for different gas hearth products. Patterns ofinterest include annual, seasonal, daily, and hourly profiles. OBJECTIVE 4. 

### Estimatethe effect ofhearth producttypes that serve as a supplemental heat source on total household gas usage. Inparticular, estimate the effect offireplaces, gas stoves, and gas logs on gas furnace, boilerusage, orelectric heat pump usage. OBJECTIVE 5. 

### Characterize the effect ofregional differences on gas usage. This includes the difference betweennorthern and southern utilities as well as other detectable regional differences. TopicalReport

- September, 1997 2 Hearth Products Meter StudyOBJECTNE 6. Collect data to help characterizeusage in units oftime (minutes or hours) as well as units ofgas (BTUs or therms). Objectives 1-4 address load forecasting, supply planning and demand side management needs. Objectives 2-4 provide information useful for customer service and billing estimation. Objectives 3 and 4 provide informationthat can 

### be used to address the appropriate DOEproduct classification for different hearth producttypes. Objectives 2,5, and 6 address the need for transferability ofdata between utilities. Finally, all objectives will result in data useful to utilities for strategic marketing needs. In addition to meeting utilities' needs for load data, the data may also be used to ensure that hearth products are treated in a reasonable and fair way by local, state, and federal regulators with regard to interests ofgas consumers and the gas industry. Participating utilities will have access to all ofthese analyses. Product manufacturers, and ultimately consumers, are also expected to benefit from design improvements that are a result ofimproved information on product usage frequency and duration. 

### 1.2 STUDY DESIGN AND CURRENT STATUS The primary intent ofthe study was to collect sufficient information to characterize the relationship between hearth products gas usage and the major factors that affect thatusage. Therefore, the study was designed to meet data requirements necessary to construct valid statistical models that may be usedto predict future gas usage. The study did not attempt to achieve a probability-basedrandom sampling ofhearth products across the United Statesbecause of 1) the difficulty in identifying the population ofhouseholds withhearth products, and 2) cost constraints associated with the study. However, construction and evaluation ofmodels under a wide variety ofconditions (weather, region, equipment, housing and occupant characteristics) will allow the models to be used, along with population characteristics, to reasonably predict usage for any given locality. Key factors that were expected to affect gas usage orpatterns ofusage were included as stratification factors inthe original study design. These included:
• Type ofhearth product, classified according to the following categories: • decorative gas logs, • vent-free gas logs, • fireplaces, • fireplace inserts, and • gas stoves. • DOE heating region (See Figure 1.1) • Age ofthe hearth product, i.e., whether itis a new appliance**(~** 1year old) orhas been used for several years (> 1year old) • Type ofhousing: single family or multi-family housing • Location ofthe hearth product within the house: living/family room orbedroom Topical Report

- September. 1997 3 Hearth Products Meter StudyUnfortunately, recruitment difficulties encountered by participating utilities prevented the study from meeting original design targets for sample size in all stratification levels. Table 1.1 below summarizes current information onthe number ofhearth products metered, through May 31, 1997, 

### inthe various strata. Additional meters will be installed by LDCsjoiningthe study for the 1997-1998 heating season. As ofMay 31, 1997, 118 households from eight LDCs are collecting usage data hourly. The current cooperating LDCs are located inBritish Columbia, Canada; Kentucky; Ontario, Canada; Indiana; Utah; New York; Wisconsin; and California. Decorative gas logs and fireplaces are the predominant hearth products being monitored. In addition, usage data is being collected onfireplace inserts, vent-free gas logs, and gas stoves. Geographically, most ofthe participants are located in DOE heating zones IV and V, representing average heating load hours between 2,000 and 3,000. Currently, one additional LDC is scheduledto begin collecting usage data during the 1997-1998 heating seasons. More LDCs from the southeast and southwest as well as LDCs that have
• Households with vent-free fireplaces, • Hearthproducts in multi-family housing, and • Hearthproducts in homes with electric heating
are actively being recruited to participate inthe study during the 1997-1998 heating seasons.

TopicalReport

- September, 1997 4 Hearth Products Meter Study**~** 'G 

## 2"


# -**~ ~**  3000 2500
0 ::!.. I**~ ~** **~** ::i 

# ""**~** :c "'- '0 '0**~** 

## VI

Figure 1.1 DOE HeatingRegions

### Table 1.1 Number ofHearth Products Metered Through May 31,1997.

New 7 0 1 0 Ow North (DOE Heating Established 16 0 2 1 0 Region IV or above) Owner Unknown 0 0 2 New 1 0 0 2 Owner South (DOE Heating Established 12 0 0 1 Region III or below) Owner 0 Unknown 3 0 0 0 Age

• Other locations include the kitchen or unknown locations.

TopicalReport

- September, 1997 6 Hearth Products Meter Study

## SECTION 2 DATA BASE DESCRIPTION

The database consists ofdaily degree day readings, hourly gas usage (CF) for the hearth product and furnace for each participant, and demographic and equipment data collected from each participant. 

### 2.1 WEATHERDATA Daily degree day readings were collected on a regular basis from the participating utilities. The readings were transferred to Battelle either in electronic format or as hard-copy. All weather datawere entered into Statistical Analysis Software (SAS III) data sets and validated, with discrepancies resolved throughcommunication withparticipating LDCs. 

### 2.2 DEMOGRAPHIC AND EQUIPMENT INFORMATION The demographic and equipment information were collected and transferred to Battelle upon installation ofthe metering equipment. The information was double entered into Paradox data sets. Inthis manner, any data entry discrepancies were resolved immediately. The datawas then downloaded into SAS® data sets for validation. The validation identified missing data and invalid responses. Any problems found inthe demographic and equipmentinformation were communicatedto the utilities so that a resolution could be made. The final demographic and equipment analysis data are maintained in SAS data sets. 

### 2.3 GAS USAGE DATA Two systems are beingused to collect hourly gas usage readings from the hearth product and the furnace. The first is a Metretek system located at Battelle for which Battelle performs all data collection activities. The second is a Metscan system located at certain utilities that have their own system and who conduct data collection in-house and transfer the data to Battelle on a regular basis. Each system collects hourly gas readings and downloads the data to theirrespective central data collection computers daily. This data is downloaded to ASCII files and read into SAS data sets for validation. Any problems are communicated with the utility and resolved as soon as possible.

·SASe is a software package used for data management and statistical analysis. Topical Report

- September, 1997 7 Hearth Products Meter StudyThe Metretek system allows a five day window on the collection ofthe hourly data. Thus ifa communications problem arises, there is usually enough time to resolve the problem before the data is lost. Very little data has been lost due to communication problems. Once the data has been validated, hourly and daily SAS data sets are created for analysis. Extensive procedures for backups, archiving, and data security have been put in place and documented. Strategies for handling missing data, adjusting for daylight savings time, and creating efficient summary data files were developed.

Topical Report-September, 1997 8 Hearth Products Meter Study

## SECTION 3 STATISTICAL ANALYSIS ISSUES,

DEFINITIONS, AND APPROACH

As discussed in Section 1, the primary intent ofthis study was to characterize hearth product gas usage, the major factors related to that usage, and its effect ontotal household load. Data summaries and statistical analyses for the large amount ofdata collected inthis study were chosen in light ofthese objectives. Belowis a discussion ofthe issues related to the data collection, handling ofmissing data, approaches to analyzing the data, and definitions ofparticularterms and diagrams used throughout this report. 

### 3.1 DATA ISSUES Hearthproductusage data collection dates summarized inthis report ranged from November 1995 through May, 1997. Datafrom households from the eight different LDCs were included inthe analyses. Although the data contains a wealth ofinformation to address study objectives, there are three primary cautions that shouldbe kept in mind when interpreting and drawing conclusions from the data: 1. Households entered the study atdifferent times. Therefore different time periods contain differing numbers ofavailable households, as well as different households. Because ofthis, some analyses are limited to only those households with data for the entire time period ofinterest (for example, for an entire heating season). However, some descriptive summaries include all available data andthe increasing number of households over time may have an effect ontrends observed inthese summaries. 2. Sample sizes are unequal and in some cases small. Forexample, while there were data for 49 decorative gas logs available for this report, there were only datafor sevenfireplace inserts, six vent-free gas logs and four gas stoves. Therefore sample size should always be taken into account when assessing the strength ofconclusions that can be drawn from the data. 3. Nineteen households had two hearth products monitored inthe home. Unless otherwise noted, the summaries presented include the total usage bythe two hearth products. These homes were not included inthe modeling analyses for this report. It is anticipated that they will be included in analyses inthe final report.

Topical Report

- September, 1997 9 Hearth Products Meter StudyThere was one household with extremelyhigh hearth productusage that was determined to be a very influential observation and a potential outlier. Since the usage data for this household appear valid and accurate, the household was included in all descriptive statistics and summaries. However, the household was excluded from some final modeling results because of its very uncharacteristic usage and its pronounced effect on model parameter estimates. Exclusion ofthe household is documented throughout the report. 

### 3.2 MISSING DATA Although the data collection equipment was designed to minimize the amount ofmissing data, problems occurred that could notbe anticipated (for example, battery failures) andresulted in missing datafor several homes. In general, the approach to missing values was to use all the data wheneverpossible, while being careful to insure that missing values did not lead to inaccurate summary information, orbias estimates such as heating season averages byweighting one month or day more heavily than another. Because ofthe nature ofthe data, different strategies were employed for addressing missing daily hearth product usage as opposedto the furnace usage. Forthe hourly data, the approach for replacing missing hourly usage 

### was the same for boththe hearthproduct and furnace. In particular, the following strategywas adopted for the furnace and hearth producthourly usage data:
• Ondays when six or fewer hours ofusage data were missing, the missing readings were replaced bythe average hourly gas usage seen in the hour immediatelyprior to and the hour immediate following the period ofmissing usage. Ifmore than six hours in a day had missing usage no replacement was made and the usage data remained missing. Forthe daily usage the following strategy was adopted:
• Addressing missing usage on a daily level was performed in a two step process. First, the hourly data was summed over a 24 hour period from midnight to midnight forming a daily total usage. Ifmore 

### than six hours ofusage were missing in a day, then usage for that day was set to missing. The second step was to considerthe number ofdays ofmissing usage. Ifthere were eight orfewer days withmissing usage in a month, a daily usage was estimated to replace the missing days. Ifmore than eight days in a given month were missing, the daily usage was not estimated and remained missing. Forboththe hearth product and the furnace the daily usage estimation process began by using a period of28 days. Ideally, daily meter readings 14 days immediately prior to and 14 days immediately following the period ofconsecutive missing days of usage were used to estimate a daily usage. Ifdaily meterreadings surrounding the period ofmissing usage were not available then eitherthe daily meterreadings from
Topical Report

- September, 1997 10 Hearth Products Meter Studythe 28 days priorto orthe 28 days immediately following the period ofmissing usage were used to estimate a daily usage. Since hearth products are not necessarily used every day, the number ofdays on which the hearth productwould have beenturned on during the missing period was estimated. Using the 28 days ofusage data discussed above, the probability of turning onthe hearth product was calculatedby counting the number ofdays the hearth product was used and dividing by 28. This "probability" was then multiplied bythe number ofdays with missing meterreadings and rounded to the nearest whole number. This number was always at least one. Using the average hearth product usage calculated for the 28 days and the probability ofthe hearth productbeing turned on, between 1 and 8 days ofmissing hearth product usage was replaced by the estimated usage. The remaining missing daily usage was replaced by the estimated pilotusage orzero depending onwhether or not pilotusage were estimated for the appliance. The estimation ofpilot usage is discussed in Section4. The method for handling the missing daily furnace usages involved a linear regression modeling ofthe relationship between the daily furnace gas usage and daily degree day readings for the 28 days described above. Using the reported degree day readings onthe days with missing gas usage, the missing usage was replaced bythe predicted daily furnace gas usage. There were ten homes for which data collectionproblems caused missing data for both the hearth product and furnace during much ofthe 1996-1997 heating season. The problems have subsequently been resolved and a full heating season ofdata should be collected during 1997-1998. As showninTable 1.1 there are currently six vent-free gas logs in the study. Unfortunately, five ofthe vent-free gas logs were affected by this data collectionproblem. Since a full heating season ofdata is only available for one ofthe vent-free gas logs, the vent-free gas logs will not be included inany ofthe usage summaries or analyses inthis report. It is also important to note thatthe sample size available for any particular analysis or data summary will vary according to the analysis. Forexample, while there were 118 households on line as ofMay 31,1997, there were only 81 households withusage datafor a complete heating season (September-May) due tothe staggered start dates and some ofthe missing data problems described above. Similarly, only 72 households met the criteria for modeling the interaction betweenthe hearth product and furnace. Due to non-responses, the sample sizes for the questionnaire data also vary. For instance, only 66 households provided information on annual income. Sample sizes are discussed and listed for the separate analyses andpresentations throughout the report.

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- September, 1997 11 Hearth Products Meter Study

### 3.3 APPROACH TO DATA ANALYSIS Data analysis began with validation ofthe data and handling ofmissing values as discussed in Section 2. This was followed by descriptive statistics and summaries which are presented in Section 4. However, this type ofobservational study where a tremendous amount of data is collected on many variables leads to unbalanced demographic data (unequal frequencies in the different classes and subclasses ofvariables) and to the confounding ofthe effect of secondary variables when attempting to assess the effect ofany given primary variable on gas usage. For example, simple average monthly hearth product usage for fireplaces with and without a thermostat can be calculated. However, while simple averages might show (hypothetically) that fireplaces without a thermostat use significantly more gas than those with a thermostat, this result might be due to the fact that more fireplaces without a thermostat had pilot lights. This hypothetical example illustrates the danger ofconfounding ofeffects. Statistical models were used to assess the effect ofmultiple factors simultaneously and reduce the possibility ofmisleading results due to the confounding ofeffects. All statistical models were implemented using Version 6.12 ofthe SAS® System. 

### 3.4 BOX PLOTS Inmany cases it is helpful to characterize notjusta single statistic (such as the average) ofa continuous variable, but rather the entire distribution. A common way that this is done in this report is through presentation ofa box plot. Figure 3-1 illustrates a box plot.

Maximum
75th Percentile Mean 50th Percentile (Median)
25th Percentile
Minimum 

### Figure 3.1 Diagram ofa BoxPlot.
Topical Report-September, 1997 

### 12 Hearth Products Meter Study

### To understand how the box plot is read, assume that it represents the distribution of annual hearth product usage across all households. The lowest and highest annual usage are represented by MINIMUM and MAXIMUM. The 25TH PERCENTILE represents the annual usage where 25% ofthe annual usages are lower and 75% are higher, the 50TH PERCENTILE, also called the MEDIAN, represents the annual usage where 50% ofthe usages are lower and 50% are higher, and the 75TH PERCENTILE is the annual usage where 75% ofthe usages are lower and only 25% are higher. The length ofthe box represents the data's interquartile range, or the difference between the 25th and 75th percentiles, which is an indicator ofdata variability. The MEAN, represented by the triangle, is the average over all the annual usages. 

### 3.5 HISTOGRAMS Similarto the box plot, ahistogram also characterizes the distribution ofa continuous variable. Figure 3.2 illustrates ahistogram. To understand how the histogram is read, assume that, similar to the box plot description, the histogram in Figure 3.2 represents the distribution ofannual hearth product usage across all households. 100

90 80 70 Ii 60 

### '0 I- 50 

### '0**~** 40 0 30 20 10

0 

### ....

# ~ '"

# ~ 

# '"

.... 

# "**~**

Heating Season Usage (CCF) 

### Figure 3.2 Diagram ofa Histogram.

Topical Report

- September, 1997 13 Hearth Products Meter StudyThe histogram discretizes continuous data in the following manner. The x-axis represents the "bins" inwhich the heating season usage is categorized. All homes that had less than 100 CCF ofhearth product usage are categorized as "0

- 

### < 100" CCF ofheating season usage. All homes with 100 to less than 200 CCF ofheating season gas usage are categorized into the second bin, "100

- 

### < 200". This continues onuntil all the homes have beenput into a bin. The total number ofhomes for which heating season usage is available is determined. Then, for eachbin the number ofhomes in the bin are divided by the total number ofhomes to calculate the percent ofthe total number ofhomes inthe bin. For example, assume there are 50 homes for which heating season usage is available and 15 homes with usage in the range of0 to 99 CCF. The bin, "0

- 

### < 100", would have a percent oftotal (15/50) • 100 = 30 %. In the above histogram, 30% ofthe homes have heating season usage in the range of0 to 99 CCF, 40% with usage of 100 CCF to 199 CCF, 20% with usage of200 CCF to 299 CCF, and 10 % with 500 CCF to 599 CCF. 

### 3.6 DEFINITION OF SEASONS Forpurposes ofthis report the four seasons ofthe year were defined as Fall (September, October, November), Winter (December, January, February), Spring (March, April, May), and Summer (June, July, August). Reference to the shoulder seasons refers generally to Fall and Spring. Instances where the shoulder season is defmed differently from the above definitions for Fall and Spring are noted in the text. 

### 3.7 SIGNIFICANT DIGITS Hourly usage data was collected on a daily basis for an individually metered hearth product and furnace in each home ofthe study. The data is downloaded daily to a central computer through an automatic reading (AMR) device for validation and processing. The resolution ofthe gas consumption dataranges from 

### Y. cubic foot (CF) to 1CF. For consistency ofcomparison, all results for metered usage data are presented in units of 1CF as a minimum. Data summaries are presented to three significant digits, orrounded to CF units.

Topical Report

- September, 1997 14 Hearth ProductsMeter Study

## SECTION 4 DESCRIPTIVE STATISTICS AND SUMMARIES

This section contains descriptive summaries ofthe questionnaire and metered usage data collected inthis study. As discussed in Chapter 3, sample size and the staggered entry of households into the study mustbe taken into account when interpreting these descriptive summaries. Inparticular, for summaries presented by hearth product type and sampling region, sample sizes may strongly influence any conclusions drawn from the simple summary statistics. 

### 4.1 QUESTIONNAIRE SUMMARIES Three questionnaires, Pre-Selection, Site Survey, and Household, were used to gather demographic and equipment information from the homeowners participating inthe study. Generally, responses tothe questionnaires were collected priorto or duringthe installation ofthe monitoring equipment. Due to incomplete responses by some ofthe households, only 101 households were available for inclusion inthe summaries. Beloware selected summaries ofthe questionnaire data. Note that because some questions were not answered for some questionnaires, the number ofresponses for each particular question is provided. Figure 4.1 and Table 4.1 characterize the households included in the study to date. Generally the homes are suburban two-story orranch homes, averaging 2,378 square feet with 7 rooms. The average age ofthe primary adults in the home is 43 years with 82% ofthe households having an annual income greater 

### than $50,000. The average household size was 3.4 people, with an average of 1 child inthe home. Information pertaining to the hearth products and furnaces included inthe study are summarized inFigures 4.2, 4.3, and 4.4 and Table 4.2. The hearth products were fairly newproducts as shown inFigure 4.2. The majority ofthe products were less than 5 years old when this data was collectedin late 1995 and early 1996. Notethat one decorative gas log was reported to be 32 years old.

Topical Report

- September, 1997 15 Hearth Products Meter Study

### ~**~** So**~**

## ~ () r;j

### ~**~** 

## ..,**~** s::**~** Wood-burning fireplace in the home? (n= 79) No 86%

Yes 1"% Urban, Suburban, or Rural area? (n= 79)

Urban

10% Suburban 77%

Rural 13% Ranch 39%

$40,001-$50,000 9% $30,001-$40,000 2% $20,001-$30,000 5% less than or equal to $20,000 2% Style of home (n= 80) Spilt level 6%

Other Three-Story 6% 1% Two-Story 48%

Annual Income (n= 66)

2"% $50,001-$75,000 29%



### Figure 4.1 Summary ofSelected Demographic Characteristics.

### Table 4.1 Summary ofSelected Household and Demographic Characteristics.



### ....,**-~'i~E··.·.···.·.:.212E8:12lliifdGillF).··**

# ••···u····}·**·MeanJ~QL** ; 

## .."

..: 

# ... : ............... •••-,eX_C· •• N ."

'!' About how many years old is your home? 17(18.9) 0 95 101 What is the square footage of your home, excluding 2,378 (776) 1,000 5,000 100 any basement or garage? How many rooms are in your house, excluding 7 (2.0) 3 15 80 bathrooms and basement? What are the ages, in years, of the adult occupants 43 (11.4) 25 77 72 living in your household? How many people are in your family? 3.4 (1.5) 1 10 101 How many children live in your household? 1.2 (1.2) 0 6 101

35
30 

# i 25**~**

# ~ 20 

# J 15 '6

### ~ 10
5
0 

# , 1

# ~ \**~** -n

## ~ 5&**~** "9.- 

# \**~ ~**  W

## ~ '3" 

# i**~** \\ '3"

### ~**~** \\ 

# 'S '3" .:;:, \\ '3"**~**

\\**~** 

### Figure4.2 Distribution ofthe Age ofthe Hearth Product, by Type ofHearth Product.

TopicalReport

- September, 1997 

### 17 Hearth Products Meter StudyFigure 4.3 illustrates the difference observed in the study between decorative gas logs and othertypes ofhearth products with regard to the prevalence ofpilot lights. Only a little over 20% ofdecorative logs had pilot lights while more than 50% ofall the otherproducts were reported to have a pilot. Note that the percentages are calculated such that homes with two hearth products have eachhearth product included separately in the analysis.

100% 100%
90"10 80% 76% 70% 

# .. 0 if 60% 

# .. .c J::**~** 50% II 5OOh. CI 

# .. 

# .. c 40% II u 

# .. :. 30% 22% 20% 10% 0% Decoratiw Gas Log (n=49) Fireplace (n=70) Fireplace Insert (n= 7) Gas Stow (n= 4) 

### Figure 4.3 Percentage ofHearth Products Reported to Have a Pilot, by Type ofHearth Product.
As illustrated inFigure 4.4, 31% ofthe hearth products can only be turned On and Off, 53% have a Low-Medium-High temperature control, and only 6% ofthe hearth products are thermostatically controlled. Three out ofthe four hearth products that are thermostatically controlled are gas stoves. Table 4.2 presents summary statistics onthe furnaces inthe study. Several questions were designed to assess the perception homeowners have about the use oftheir hearth product. Responses to these questions across all hearth product types are illustrated in Figures 4.5 and 4.6.

Topical Report-September, 1997 18 Hearth Products Meter Study**~** "ti 100% 

# [**~ ~**  c :t I**~** "ti 80%**~** :! 0- l1:I ,:-,



## .... '0 '0 '-I 60% CD en c:: 0 c. en CD 

## a:: 

# - 40% c:: CD



## .... (,)


## .... '0 CD 

### a.. 20%

Overall (n=64) Decorative Gas Log Fireplace (n=12) Fireplace Insert (n=6) Gas Stove (n=4) (n=42) a2I Low-Medlum-High 53% 67% 8% 67% 25% 31% 24% 67% 33% 0%**~** Thermoltat 6% 2% 0% 0% 75% 2 0% 

### Figure4.4 Type ofTemperature Control, Overall and for EachType ofHearthProduct.

### Table 4.2 Summary ofSelected Household and FurnaceEquipment Characteristics, by Hearth Product.

Does the fireplace have a fan to blow the warm air into the room? Was it necessary to build the surrounding framework, masonry or enclosure for the ? Does your furnace have an electronic ? Does the furnace have a vent or flue?
Question
What is the input BTU rating for the furnace?

What is the output BTU rating for the gas furnace?

How old is the gas furnace (years)?
What is the heating efficiency rating of the furnace in %AFUE? 73% (n=8) 27% (n=3) 89% (n=8) 11% = 1 67% (n=12) 33% (n= 6) 71% (n= 15) 29% n= 6) 76% (n=16) 24%

100,351 (27,965) 34,000-200,000 42 81,216 (18,674) 30,600-112,000 17 6 (7) 1-30 38 75% (1%)

74-75 2 0% (n=O) 100% (n=6)

20% (n=1) 80% (n=4) 43% (n=3) 57% (n=4) 43% (n=3) 57% 25% (n= 1) 75% (n=3) 67% (n=2) 33% =1 0% (n=O) 100% (n = 2)

50% (n=2) 50% (n=2) 50% (n=2) 50% Mean (Standard Deviation) Minimum - Maximum 117,857 (27,212) 80,000-150,000 7 102,300 (21,382) 69,000-120,000 5 12 (8) 2-22

6 69% (5%)

63-75 5 N 114,250 (29,193) 80,000-140,000 4 87,200 (19,807) 72,000-109,600 3 11 (4) 7-17

4 78% (4%)

75-80 2 23% (n=10) 77% (n=33) 11% (n= 1) (n=8) 75% (n=27) 25% (n= 9) 80% (n=35) 20% = 9) 41% (n= 17) 59%

103,182 (27,154) 57,000-200,000 44 87,177 (21,511) 55,000-160,000 22 9 (10) 0-36

43 65% (14%) 52-80

3100%

60% 54% 40010 34% 25% 20% 21% f--- 14% 

# I I 11% 5% 

# I 

# I I I 0%



### Figure4.5 Reason for Purchasingthe Hearth Product (N=80).

100%
80%
60% 48% 40% 19% 21% 20% 4% 3% 5% 00,(, 

### r l 0°,(, 1% 0%



### Figure4.6 PrimaryReason Hearth Productis Typically Used (N=79).
Topical Report

- September. 1997 21 Hearth Products Meter StudyFigure 4.5 shows that across all the homeowners in the study, the most frequent reason for purchasing the hearth product was "Appearance." The primaryreason for using thehearth product was "Looks and Heat," as shown inFigure 4.6. 

### 4.2 HEARTH PRODUCT AND FURNACE GAS USAGE SUMMARIES This section provides summaries ofthe heating season, monthly, daily, hourly, and pilot usage as well as the patterns ofusage by the hearthproduct owners. Many ofthe summaries are presented over all households and by the type ofhearth. Because ofthe unbalanced nature ofthe data, i.e. varying sample sizes across the type ofhearth product, sample sizes will bepresented with each analysis. The datato be included in the metered usage summaries was collected from November 29,1995 through May 31, 1997. Only partial heating season usage data is available for many ofthe homes during the 1995-1996 heating season because ofthe staggered start dates

- many utilities began installing in late November, 1995 with installations continuing through October of 1996. The cut-offdate for data inthis report was May 31, 1997, to meet report deadlines while ensuring that the data was validated and summarized correctly. 

### 4.2.1 Heating Season Gas Usage Figure 4.7 presents a histogram ofthe distribution ofthe average heating season gas usage bythe type ofhearth product, while Figure 4.8 illustrates the same information in a box plot. Forthis presentation, only usage inthe 1996-1997 heating season is included and is referred to as the total heating season usage since the usage was collected between September 1, 1996 and May 31, 1997. Eighty-one ofthe 114 homes for which hearth produce usage was available had less than 30 days ofmissing data and are included inthe analysis with 44 hearth products having a complete heating season ofusage with no missing data. The histogram in Figure 4.7 shows that more than 35% ofthe hearth products had an average heating season usage between 25 CCFs and 75 CCFs. Nearly 20% ofthe fireplace inserts had heating season usage between 425 and 525 CCFs.

Topical Report

- September, 1997 

### 22 Hearth Products Meter Studyiii 0



### .... '3 tt. 

## 80.-------------------------------------------------------------------,

60

40 6,
20 )( 

### , . . \ 

### ,. i**~** , \ 

### , . . \ 

### , \ \ i \ \ '\ \ 

# • ,.\ 

### i \ I
. 

## / \ i \
,. i 

### i \ ! \i**~ ~** **~ ~**  

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### # #**~ ~~** **~ ~** **~ ~** **~ ~** **~**

... rt"**~f)' ~'**  .vf)' ".rt"**~f)'** -.rt"**~f)'** f)rt" Heating Season Usage (CCF) I_Overall -.-Decorative Gas Log --8-- Fireplace ·... h·
.. Fireplace Insert**-·~-** .. Gas Stove 

## I Figure 4.7 Heating Season (September, 1996

- May, 1997) Hearth ProductGas Usage, by Type ofHearth Product

-- Histogram.
Figure 4.8 shows that the average heating season hearth product gas usage ranged from 105 CCF for the 34 fireplaces to 171 CCF for the 6 fireplace inserts. Decorative gas logs, with the largest sample size, had an average of 120 CCF for the heating season. Both figures illustrate the variability inheating season hearth product usage with usage ranging from 0 CCF to 824 CCF and 75% ofthe population using less than 300 CCF for the heating season.

Topical Report

- September, 1997 23 Hearth ProductsMeter Study900
BOO
700 CL 

# a BOO 

# t 500 :::l 8 

## J400 g> 

# i 300
200
100

# ~

0 

# \ 

# \ '\ '5

### ~ 

# ,**~ ~**  1)**~** 

# \ \

\ '5 

# , '5 $



# , '5 $



## ,**~** 

### Figure 4.8 Heating Season (September, 1996

- May, 1997) Hearth Product Gas Usage, by Type ofHearth Product

- Box Plot.



### 4.2.2 Monthly 

### Gas Usage The average monthly gas usage from February, 1996 through May, 1997 for eachtype of hearth product is presented inFigure 4.9. The summarybegins in February since only a few hearth products were being monitored in November and December of 1995 and the bulk ofthe monitoring installations did not occur until mid and late January. Because ofthe staggered start dates the number ofhearth productsbeing included inthe monthly average increases overtime leveling offin October of 1996. InDecember, 1996 the number ofhearth products included in the averages decreased by 10 for one LDC, but nine were added from another LDC. No new installations occurred from late December, 1996 through May, 1997. Figure 4.9 shows that generally the hearth product usage begins in September. Usage increases through the Fall, peaking in December and January for all hearth producttypes. Usage remains nearly constantin February and March and then decreases in April and May.

Topical Report

- September. J 997 

### 24 Hearth Products Meter Study**~** "t; O· 35 

### fa.**~ ~**  c ::t 30 I**~** "ti**~** ::i**~** 25**~** 

### .....**~** 'I 20

15

10

5

o Feb-98 Mar-98 Apr-98 May-96 Jun-98 Jul.98 Aug-98 Sep-98 ()Q.98 No¥-98 [)ec..98 Jan-97 Feb-97 Mar-97 Apr-97 May-97 Feb-98 Mar-98 Apr-98 May-98 Jun-98 JIJI.98 Aug-98 Sep-98 ()Q.98 No¥-98 [)ec..98 Jan-97 Feb-97 Mar-97 Apr-97 May-97 OOwral 20.2 21.9 13.8 7.8 4.2 3.5 3.2 3.7 9.8 18.2 21.2 23 15.8 18.2 10.1 5.4 COecoratw Gas Log 17.5 23.8 10.5 8.1 2 0.9 0.7 2.8 8 17.8 25.7 24.3 13.4 13.2 8.8 3.8 ORrepIace 20.8 22 17.4 10.2 7 8.8 8.4 5.2 11.2 13.8 15.1 21.2 17.2 18.4 12.1 8 • Fireplace IIIB1 29.7 17.1 9.8 3.8 0.4 0.2 0.2 3.8 18.7 23.8 28.5 28.8 19.8 19.1 14.8 7.8 GlGasSWt 15.8 11.1 8.2 3.8 2.8 0.7 0.7 2.3 5.4 12.7 18.1 20.8 15.2 13.7 13.5 4.7 

### Figure 4.9 Average Monthly HearthProduct Gas Usage, Overall andby Type ofHearth Product.

### 4.2.3 Daily Gas Usage All available data collected inthe 1996-1997 heating season was included in the summary ofthe daily gas usage. Figure 4.10 presents a load profile ofthe ratio ofthe average daily usage to the maximum daily usage during the heating season for the hearth product and gas furnace separately. Included inthe graphs are the average daily degree readings associated with each day ofusage from September 1, 1996 through May 31, 1997. The loadprofiles in Figure 4.10 indicate that overall and within each type ofhearth product, the hearth product usage is less related to weather than the gas furnace usage with a resulting flatter load profile. On average there is an increase inhearth product usage as the weather gets colder, but the increase appears to level offduring the heart ofthe heating season except for a few spikes on colder days. The usage decreases slowly as the weather gets warmer. Generally, the usage levels are similar across all hearth product types. 

### 4.2.4 Hourly Gas Usage Similarto the daily gas usage summaries, the hourly summaries are presented as load profiles. ForJanuary, 1997, the hearthproduct, furnace, and total hearthproduct and furnace average hourly gas usages are compared across a 24 hour period bythe type ofhearth product are presented in Figure 4.11. Across all the hearth products, the hourly use pattern throughout the day appears to be very similar. Generally, the furnace is the major contributorto the total heating load assuming the total heating load is only the furnace and the hearth product usage throughout the day. The peak usage for the furnace occurs in the morning hours while the peakusage for the hearth product occurs inthe evening hours. A peak also occurs inthe morning hours for the decorative gas logs though this peak is much lower than the evening peak. On average, the hearth products' evening peaks add to the evening heating load, butdo not change the peakusage hour within a day. Forthe decorative gas logs, fireplaces, and fireplace inserts, when the hearthproduct is used in the evening, the furnace gas usage appears to decrease. An assessment ofthe effect ofhearth product usage onthe gas furnace usage accounting for weather is provided in Section 6.

Topical Report

- September, 1997 26 Hearth Products Meter StudyCNeralI**~~~~--~--~--~--~--~--~--~--T** 

# ---------- -



# ---------- - Gas SIcMI**~~~~~--~--~--~~--~~~~** 

# ---------- - 8

8 DecoraIiYe Gas Log

8

### ~~~~~~~~ 

# ---------- - Ftreplace Insert



# ..I



# ..**~~~~--~--~--~--~--~--~--T_~~** 

# ---------- - 8

Figure 4.10 Average Daily Hearth Product and Furnace Gas Usage as a Percent 

### ofthe Maximum Daily Usage by Type ofHearth Product.
Topical Report

- September, J 997 27 Hearth Products Meter StudyOverall Decorative Gas Log**0,5.r------~**

Rreplace Rreplace Insert**o~'------------------r=-~~------~--~~** 

# I :::::.,. I'ImIoe rd HIaIh -**~** .......... HIaIh_

Gas Stove**~'------------------r==================~l** 

### I:::;:.,., I'ImIoe rd HIaIh -

........... HeII1h_



### Figure 4.11 Furnace, Hearth Product, and Total Furnace and Hearth Product Average Hourly Gas Usage by Type ofHearth Product for January, 1997.
TopicalReport

- September, 1997 28 Hearth Products Meter Study

### 4.2.5 Pilot Usage Using the hourly data, the hourly pilot usage was estimated for each hearth product. The estimated hearth product pilot hourly gas usage for eachtype ofhearth product is provided in Figures 4.12 and 4.13. Forthe 59 homes that indicated they have a pilot on at least one hearth product, the fireplace pilot usage had the most variability ranging from 0.5 CF to 2.83 CF per hour, with most ofthe fireplace pilots estimated to use 1.3 CF per hour. More 

### than 60% ofthe decorative gas log pilotusage ranged between 0.75 CF to 1.25 CF. Seventy-five percent ofthe fireplace insert pilots and 50% ofthe gas stove pilots had an average hourly pilot usage of 1.25 CF or less.

70

60 4 iii 1\ 1\ , , '\ I \ I \ 50**:'~** I \**~** I \ I \ i·, " r \ '. I \ : I \ 40 I \ 

# J I \ I \ r \ '& I \ tt- I \ : 30 \ ,. \ : i**~.** ;' \ " \ :' \ 20 :;' \ \ '. \ '; \ I

0-<.25 .25-<,50.50-<.75.75-<1.01.0-<1.25 1.25-< 1.5-<1.751.75-<2.0 2.0+ 1.50 Eltlmltad Hourly Pilot U
..ga (CF)
• Overall --<>--Oecorative Gil Log - -8- - Fireplace .•• . .t.

....Fireplace Insert
.. _--)11[--. Gal Stove 

## I Figure4.12 Distribution ofthe Estimated Hearth ProductHourly Pilot Gas Usage byType ofHearthProduct

- Histogram.

Topical Report

- September, 1997 

### 29 Hearth Products MeterStudy3.0
2.5

### ~

### ~ 2.0 ::::>

### ~ 1.5 

# f 

# I to**~** 0.5
0.0

# \**~** ':!\

### ~ 

# \ 

# \**~**

'S 

# \**~**

### ~ II 'S**~** \I 

# S 'S**~** II 'S £) \I 

### :9 Figure 4.13 Distribution ofthe Estimated Hearth ProductHourly Pilot Gas Usage by Type ofHearthProduct

- Box Plot. 

## 4.3 PEAKDAY AND PEAKHOURUSAGE Peak day and peak hour gas usage is ofinterest to utilities for many reasons including supply planning and load forecasting. As described in Section 2 utilities reported daily degree readings beginning withthe first installation ofmonitoring equipment intheir service area. Forthis section, the coldest days inthe 1996-1997 heating season were calculated. Note that the gas usage for many ofthe hearth products in the study were not being monitored when the actual peak weather day occurred in the 1995-1996 heating season, therefore data from this heating seasonwas not included inthis analysis. Forthe 1996-1997 heating season, Figure 4.10 presented earlier shows a load profile of the ratio ofthe average daily usage to the maximum daily usage during the heating season for the hearth product and gas furnace separately. The figure shows that, on average, peakhearth product usage orvery nearthe peak is attained mUltiple times throughouttheheating season. 

### In addition, thehearth productpeakusage is not as highly correlated with weather as the furnace usage. Notethat 100% was not achieved for either the furnace orthe hearth product since the

Topical Report

- September. 1997 30 Hearth Products Meter Studypeak day gas usage was different for many ofthe homes and the graphs present the average ofthe percent ofusage to the maximum usage taken across households. An examination ofthe load profiles presented inFigure 4.10 indicate a flatter load profile for hearth products than for furnaces. The load factor for furnaces is often calculated as the average daily furnace usage divided by the usage on the peak weather day (or system peak). An identical statistic cannot be calculated for hearth products because ofthe occurrence ofzero hearth product usage onthe peak weather day for some households. However, the inverse ofthis statistic, usage onpeak day divided by average usage, canbe calculated. As an indicator ofhow much the hearth product contributes during periods ofpeak cold weather conditions, the average ratios for hearth products are presented inFigure 4.14. To provide additional information onthis question Figure 4.15 presents the average, across households, ofthe ratio ofthe average usage on the top five peak weather days to the average usage on the top 45 weather days for boththe hearth product and the furnace. This statistic provides a better measure ofwhether hearth product usage is increased during periods ofextremely cold weather over its normal usage during cold winter weather. Figure 4.15 indicates that average hearth product usage onthe top five coldest days averaged over 1.5 times as much as average hearth product usage onthe top 45 coldest days. In fact, for all appliances except the fireplace, the increase in peak usage, on a percentage basis, exceeded the increase inpeakusage exhibited by the furnace. Preliminary statistical modeling results discussed in Section 6.3 also indicated a statistically significant increase in hearthproduct usage, after adjusting for weather, onthe peak weather days (five coldest days). This preliminary assessment suggests that while the hearth product load profile may be flatter than the furnace, the hearth products may likely be used during peakperiods of extremely cold weather. This also indicates further efforts to characterize this effect maybe worthwhile.

Topical Report-September, 1997 31 Hearth Products MeterStudyCD CI a:l 1/1 :l >- a:l 

### c CD CI 

## e CD**~** 0 

## ... CD CI a:l 1/1 :l >- a:l C**~** a:l CD g,. 

# - 0 .2 

# .. a:l Ill: 8 7 6 5 4
3 2 1
0 Overall (n-SO ) Decorative Gas Log Fireplace (n=32 ) (n-39 ) Fireplace Insert (n-6 ) 

### 10 Hearth Product. Gas Furnace 

### 1 Gas Stove (n-3 )


### Figure4.14 Ratio ofthe PeakWeatherDay Gas Usage to the Average Daily Gas Usage During the Heating Season for the Gas Furnace and Each Hearth Product Type.

Topical Report-September, 1997 32 Hearth Products Meter Study

## Ic


## ... '" GI a.**~**

### gle 0 GI 

## i :J S**~** 

### '" c 11 GI a. II)

### gI

### g 

# • " :J '8 

## i II: 2 1.8 1.6 1.4 1.2

1 0.8 0.6 0.4 0.2

0 Overall (n-81 ) Decorative Oa. Log Fireplace (n-35 ) (n-37) Fireplace In.ert (n-. ) 

# 10 Hearth Product. Oa. Furnace 

### I Oa. Stove (n-3 )


### Figure 4.15 Ratio ofthe Gas Usage ofthe Five Coldest Days to the Gas Usage on theTop Forty-Five Coldest Days for the Gas Furnace and EachHearth Product.
Figure 4.16 provides a comparison ofthe average hourly gas usage during January, 1997 for the hearth products, furnace, and total hearth product and furnace tothe hearth product, furnace, and total hearth product and furnace gas usage onthe peak weather day that occurred during January, 1997 for the respective utility. This figure provides an indicationthat onthis peakweather day the hearthproduct may be a supplemental heat source andthe gas usage from the hearth product may shiftthe daily peak from the morning to evening hours.

TopicalReport

- September, 1997 33 Hearth Products Meter StudyOverall 1.0-r;========;--------------,**~_"""PIocIJcI** &-+--<>
_ Funooo e--&-e bill
_ FunocoH' +**-~ ~**  t-IeII1h ProducI CL .8 .Q -(lo- -E'J fufWIce**~** 0**1L-.~_~_bIII~~Rm_** ..**~IP_~** 

# 1M**~** 

# f**~4**

# f~

Rreplace

Gas Stove 1.0-r;===========;--------------,**o.o~-** -

1 23' 5 6 7 8 •**~** n**~ ~**  u**~ ~**  D • S m**~ ~** **~ ~**  Decorative Gas Log 1.0-r;=========,------------,

Hour Rreplace Insert**In-r;=~==_==....,,==PIocIJcI====,--------­ ~--**  &-&-e 1:UI**~ ~**  + --..... I'8wIh ProcU:t [L 0B <9'-**~** Ft.mIc8**~** . IL"--<>-"_bIII_FunocoH'
_______ -' 

# I o.**~** 

# i 0.4

# t~ «

Figure 4.16 Comparison ofthe Average Hourly Furnace and Hearth Product PeakDay Gas Usage to the Average Hourly Furnace and Hearth Product Gas Usage duringJanuary, 1997, by Type 

### ofHearth Product. TopicalReport

- September, 1997 34 Hearth Products Meter Study

## SECTIONS CHARACTERIZATION OF SUBSETS OF CUSTOMERS

Initial examination ofplots ofhearth product usage for different customers indicated widely varying patterns ofusage. Some customers are very heavy users; some are very light users. Some display a heavy interaction with the furnace; others display little orno interaction. Some use the hearth product extensively early in the season; others delay use ofthe hearth product until later in the heating season. For example, Figures 5.1 through 5.4 presentboth furnace and hearth product usage plotted versus degree day reading for four households with markedly different usage patterns. Figure 5.1 illustrates a household where the hearthproduct appears to be used as a significant supplemental heat source. Figure 5.2 presents a household with less hearth product usage but where the hearth product still has an obvious relationship with weather. Figure 5.3 presents a household with hearth product usage that appears independent of weather. Finally, Figure 5.4 presents an example ofa hearth product with only sporadic usage.

14 13 12 0 11 10 0 9 0 0 0 0 8 0



### o 5 10 15 20 25 30 35 40 45 50 55 60 65 70 Daily Degree Day Reading Legend:**.~-** - Hearth Product <> -<J -., Furnace 

### Figure 5.1 Example ofa CustomerWith Very Heavy Hearth ProductUsage thatMay Serve as a Supplemental Heat Source.

Topical Report

- September, 1997 35 Hearth Products Meter Study14 13 o 12 o a 0 9-' 11 , 0 10 o 0 0' 9 o , 0 o rL () 8 Q. Q) 7

### ~ 6 :::> 5 4 3 2 1 0 0 5 ID ffi 

### ro**~ ~** **~ ~** **~** 

### ro**~** 00**~** 

### m Daily Degree Day Reading Legend:**~-** - Hearth Product 0- -<) -" Furnace 

### Figure 5.2 Example ofa Customerwith Moderate Hearth Product Usage Significantly Related to Weather.
14 13 12 11 10 9 o o 0 rL 

# a 8

# ~ 7 6 :::> 5 4 3 2 0 

### o 5 10 15 

### ro 25**~ ~** **~ ~**  

### ro**~** 00**~** 70 Daily Degree Day Reading Legend:**~---** Hearth Product 0--<)-" Fumaoe 

### Figure 5.3 Example ofa Customer With Regular Hearth Product Usage Independent of Weather.
Topical Report

- September, 1997 36 Hearth Products Meter Study14 13 12 11 10 9

### ~ 8 

### g Q) 7 

# i' 6 ::> 5 4 3 2 o o 0 ,;9

o

o



## ---------------------------- 

### o 5 

### ro**~ ~** **~ ~** **~ ~** **~ ~** **~** 00 ffi 

### ro Daily Degree Day Reading Legend:**~-- ~**  Hearth Product ()- -0 -" Rmace 

### Figure 5.4 Example ofa CustomerWith Only Sporadic Hearth ProductUsage. Subsets ofcustomers were identified according to three different usage characteristics: total hearth product usage, usage inthe shoulder season, and net increase intotal household heating load in the winter. Classification ofcustomers into a HIGH group for each ofthe three usage characteristics (based onbeing inthe top 20% ofusage for the particular characteristic) revealed strong correlationbetweenthe users inthe HIGH group for eachusage characteristic, indicating that those users who have the highest total hearth product usage also often use the hearth product heavily in the shoulder seasons and are also estimatedto generate the greatest net increase intotal household heating load inthe winter.

Topical Report

- September, 1997 37 Hearth Products MeterStudy

# SECTION 6 RESULTS-FACTORS RELATED TO HEARTH PRODUCT USAGE
Statistical methods were used to assess the relationship betweenhearth product gas usage and major factors that may affect that usage. Identifying factors related to hearth product usage presents a special challenge because ofthe wide range offactors influencing the use ofhearth products. Unlike furnace usage, which is highly dependent on weather, house size, and efficiencyrating, hearth product usage mayormay not be explained by weather and equipment or household characteristics. Identification offactors related to hearth product usage was accomplished through a series ofstatistical analyses used to construct models to predict hearth product usage that were included in a proprietary report for participants in the study. The intent was to develop models that use equipment, building, demographic, region, weather, and type ofday information to characterize hearth product usage and patterns ofusage. Preliminary informationregarding whichpredictor variables were associated with hearth product usage was obtained from crosstabulation tables and simple correlation statistics that indicate changes in gas consumption related to changes in the predictor variable. The advantage ofstatistical modeling was the ability to assess multiple factors simultaneously. 

### 6.1 DESCRIPTION OF AVAILABLE DATA Hearth product usage data collection dates summarized inthis report ranged from September, 1995 through May, 1997. There were limits onthe amount ofinformation that could be extracted from the data. This was primarily due to the staggered dates ofentry into the study for households from the various LDCs (local distribution companies). Itis expected that the models may change somewhat and comparisons and conclusions become more clear as more data can be included inthe analyses. Another limitation ofthe data was the unequal numbers ofeach hearth product type. For example, data from 107 households were used inthe analyses inthe following sections. Ofthese, 49 have Decorative Gas Logs, while only four have gas stoves. The unbalanced nature ofthe data makes it difficult to discern differences among the groups. One household with extremely high hearth product usage was determined to be an influential observation and a potential outlier. The usage from this household was very influential onmodeling results and was excluded from the final analyses onwhich conclusions presented in this report are based. Also note that the homes with two hearth products inthe home were not included inthe following analyses. Itis expected that analyses will be performed inthe future onthese homes.
Topical Report

- September, J 997 38 Hearth Products Meter Study

### 6.2 STATISTICAL METHODOLOGY The relationship between hearth product usage and the possible predictors was assumed to be linear and have the following form: Hearth Product Usage 

## =

# Po + pj*Predictor j

### + error, where i 

## = 1to the number ofpredictors and 

### error is random noise assumed to be normally distributed, with mean zero and variance 0 2 independent ofthe predictors. Numerous variables exist that could be important predictors ofhearth product usage. Thus, priorto the assessment of the statistical models, it was necessary to reduce the number ofvariables considered to be possible predictors. A few variables were considered ofprimary interest and were included in all models, regardless ofthe usage period (heating season, season, month, or day). These included degree day measures, hearthproducttype, and the presence ofa pilot light. These three variables were included in all ofthe models based ontheir assumed predictive power. 

### In addition, usage period indicators (heating season, season, and month), demographic and equipment variables correlated with hearth product usage, and classification variables such as DOEheating region and LDC service area were assessed to determine the best predictive model for hearth product usage. The steps in the variable selection/reductionprocess included an assessment ofstatistical correlations, combination ofvariables, stepwise regression, R2 analysis, and professionaljudgement. 

### 6.3 MODELING ANALYSIS RESULTS The statistical modeling analyses indicated that factors most significantly related to hearth productusage include:
• Degree day measures • Presence ofa pilot light • Hearthproducttype • Type ofday

- weekend/weekday holiday

- peak day. LDC service area and DOE heating region were also assessed as candidate variables for each model. However, in general, after including the effect ofweatherinthe model, no additional effect ofservice area orregion was detectable. Likewise, after including the effect of weather inthe models, the additional effect ofseason ormonth was usually not statistically significant, although there were indications ofhigher usage inDecember and January.

Topical Report

- September, 1997 39 Hearth Products Meter Study

## SECTION 7 MODELS TO ASSESS THE HEARTH PRODUCT-FURNACE INTERACTION

A question ofprimary interest is how does hearth product gas usage interact with furnace gas.usage, and what is the resulting net impact ontotal household heating load. There are many possible scenarios. The use ofthe hearth product may be supplemental to furnace usage or hearth product usage may replace furnace usage. Hearth products maybe used as a means of localized heating which would reduce the total household heating gas consumption, orthey may heat a previously unheated orpoorly heated space, thereby increasing total consumption. Some hearth product types may affect the central heating system gas usage more than others due to equipment and venting characteristics. This section presents models and analyses that address these issues. The effect ofa hearth product ontotal household usage may be broken into two separate effects. First is the effect ofthe actual installation ofthe hearthproduct. This may be the result ofclosing (or opening) a previous fireplace vent (such as replacement ofa previous woodburning fireplace). Since the Hearth Product Meter Study does not include any homes that were metered both before and after installation ofthe hearth product, the first effect was not able to be assessed directly from the data currently available to this study. The second effect ofa hearth product on total household usage concerns how actual**~** ofthe hearth product affects the central heating system usage. Forexample, for eachtherm of fireplace usage, howmuch is the furnace usage increased or decreased. During periods ofregular furnace usage (i.e., the winter months), the effect ofhearth product usage on furnace usage can be estimatedby statistical models. It should be recognized that ifthe hearth product is used 

### in the shoulderperiods to replace furnace usage altogether, that effect will not be captured in these models. To illustrate howhouseholds can differ in the observed interaction betweenhearth product and furnace, Figures 7.1 and 7.2 present data from households with markedly different interactions with the furnace. Figure 7.1 presents data from a household in the study that illustrates a likely interaction between use ofthe hearth product and furnace. Days with heavy hearth product usage have lower furnace usage. Figure 7.2 illustrates this interaction for the same household byplotting furnace usage adjusted for weather versus hearth product usage adjusted for weather, showing a clear relationship between the two. Figure 7.3 presents data from a different household in the study that suggests little orno interaction between hearth product and furnace usage. Furnace usage appears independent ofthe hearthproductusage. In Figure 7.4, the plot offurnace usage adjusted for weather versus hearth product usage adjusted for weather also shows no relationship, only a random scatter ofpoints for this household.

Topical Report

- September, 1997 

### 40 Hearth Products Meter Study

### 7.1 RESULTS OF MODELING THE INTERACTION A modeling approach was used to assess the impact ofhearth product usage on furnace usage inthe winter months. The following linear regression model wasused: Daily Furnace Usage 

## =

## Po +

## PI x Daily Degree Days 

### +

## P2 X Daily HearthProduct Usage In this model, the parameter

## P2 (the slope parameter for Daily Hearth Product Usage) represents the decrease orincrease in furnace usage (in CCFs) for each CCF ofhearth product usage, after adjusting both variables for the effect ofweather. This model was fit to each household using data from December, January, and February. The households included were limited to those that had at least 10 days ofhearthproduct usage and 10 days offurnace usage during the relevant period. A total of98 households were used inthis modeling effort. The average estimated slope for the 72 households was -0.33, representing a decrease of 0.33 CCF in furnace usage for every CCF ofhearth product usage. Over 70% ofthe slope estimates were negative indicating that most homes did decrease furnace usage as a result of hearth productusage. Assuming that the slope parameters for these households represent a random sample from a normal distribution ofall such estimates, the average slope estimate (-0.33) canbe interpreted as the average decrease in furnace usage due to hearth productusage, after adjusting for weather. Thus, on average, 1 CCF ofhearth product usage leads to a 0.33 CCF decrease in furnace usage, implying that the remaining 0.67 CCF represents a net increase to the total household load. Therefore, on average, based onthe data analyzed to date, 67% of the hearth productusage can be characterized as incremental load. Itis important to note that results based onthe current data included 

### inthis report are heavily influenced by homes with decorative gas logs and fireplaces which represent the majority ofhomes summarized inthis report.

Topical Report

- September. 1997 

### 41 Hearth ProductsMeterStudy14 13 12 11 10 9 CL 

# a 8

# ~ 7 6 :::> 5 4 3 2 

### ° ° 'be



### o 5 

### ro ffi**~ ~** **~ ~** **~ ~**  

### ro**~** 00**~** 

### m Daily Degree Day Reading Lagend: ._- - Hearth Product 0- -<l

- 8 Furnace 

### Figure 7.1 Usage Data from a Household with Significant Interaction Between Hearth Product Gas Usage and Furnace Gas Usage.

2

'.



## . - 

## ..



# .,.. .

# .. --,-, 

## . '''''.' 

## ". fi-
_ • • -'' J,**~** .' • -, •

o 

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## .

## ",: . 

## :.**.--;~----:** .: 

### ..... : 

# ... :-'-
.......**I~.** , • 0 ' 

## o. -,0 0,**-2~~~~~~~~~~~~~~~~~~**__**~~~~** -2 -1 o 2 Hearth Product Dally Gas Usage (CCF) Adjusted for Weather 

### Figure 7.2 Furnace Usage Adjusted forWeatherPlotted Against Hearth Product Usage Adjusted for Weatherfor a Household With SignificantInteraction.
Topical Report

- September, 1997 42 Hearth Products Meter Study14 13 12 11 10 9 8 7 6 5 o o



# . .' 

# .. . :

# .. •• I o

o



# . . .

# .

o 5 10 15 20 25 30 35 40 45 50 55 60 65 70 Daily Degree Day Reading Legend: .--**~** Hearth Product 

### Figure 7.3 Usage Data from a Household with Little Interaction Between Hearth Product Gas Usage and Furnace Gas Usage.

6 

# i 5 4**~** 

# ! 3**~** 2

# ~ 1 

# J 0

### ~ -1

## ~ 

# j -2 -3 

# . ........ 

# . . .

. -. . 

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# . 

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--- -.-; -**-:~.'~** ;-(-:_

- _._ - _.___._ ...e __; __ .!
......_____).
________ . _______________ . __________ _ .:**.\~**

# .. :: 

### .. 

## ... .

-2 ••**~** 111,- ,;:.,.: • 

### . 

## .. ," 

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## .. .",. 

## .. . . ...:

## .. . 

## -.

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# . .. 

## - 

## .. . 

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# ..
-1 0 1 2 3 4 5 6 Hearth Product Dally Gas Usage (CCF) Adjusted for Weather 7 

### Figure 7.4 FurnaceUsage Adjusted for WeatherPlotted Against Hearth ProductUsage Adjusted forWeatherfor a Household with Little Interaction.
TopicalReport-September, 1997 43 Hearth Products Meter Study

### 7.2 FACTORS RELATED TO THE INTERACTION BETWEEN 

## HEARTH PRODUCT AND FURNACE Additional analyses were conducted to identify variables that could be used to predictthe estimated effect ofhearth product usage onfurnace usage. Four different variables were tested individually for their effect onthe interaction. None ofthe four variables (hearth product type, DOE heating region, LDC service area, and location ofthe hearth product) had a statistically significant relationship with the hearth product-furnace interaction using data available for this report.

TopicalReport

- September, 1997 

### 44 Hearth ProductsMeter Study

### j j j j j j j j j j j j j j j j j j j j j j j J 

### j j j j j j j j j j j j j j j j j j j j jjj

j jHeadquarters 

### Gas Research Institute 8600 West Bryn Mawr Avenue Chicago, Illinois 60631-3562 3121399-8100
Washington Operations Division 

### Gas Research Institute 1600 Wilson Boulevard Suite 900 

### Arlington, Virginia 22209 7031526- 7800 

# I