9-B-i

APPENDIX 9-B. ADDITIONAL DATA ON SHIPMENTS OF RESIDENTIAL 

BOILERS

TABLE OF CONTENTS

9-B.1 HISTORICAL SHIPMENTS DATA ................................................................... 9-B-1

9-B.1.1 Appliance Magazine Shipment Data .................................................................... 9-B-1

9-B.1.2 AHRI Shipment Data............................................................................................ 9-B-2

9-B.1.3 Energy Star Shipment Data................................................................................... 9-B-2

9-B.1.4 Summary of Historical Data by Product Class..................................................... 9-B-2

9-B.1.4.2 Disaggregation of Hot Water and Steam Boilers................................ 9-B-3

9-B.2 FRACTION OF RESIDENTIAL BOILERS SHIPPED TO COMMERCIAL 

BUILDINGS......................................................................................................... 9-B-7

9-B.3 PROJECTED SHIPMENTS BY PRODUCT CLASSES..................................... 9-B-8

LIST OF TABLES

Table 9-B.1.1 Historical shipments of boilers in the period 1960-1986 and 1990-

2008............................................................................................................ 9-B-1

Table 9-B.1.2 Historical shipments of boilers in the period 1969-2000........................... 9-B-2

Table 9-B.1.3 Historical shipments of residential boilers in 1993 1. ................................ 9-B-3

Table 9-B.1.4 Historical shipments data of hot water and steam boilers reported by 

AHRI.......................................................................................................... 9-B-4

Table 9-B.1.5 Historical shipments data of hot water and steam boilers reported from 

a PNNL report.3 ......................................................................................... 9-B-4

Table 9-B.1.6 Historical Shipment Data of Boilers.......................................................... 9-B-4

Table 9-B.1.7 Adjusted Historical Shipment Data of Boilers........................................... 9-B-6

Table 9-B.2.1 Residential Boilers’ Shipments by Building Types................................... 9-B-8

LIST OF FIGURE

Figure 9-B.3.1 Total Projected Shipments of Residential Gas-fired Steam Boilers in the 

Base Case and Each Standards Case.......................................................... 9-B-9

Figure 9-B.3.2 Total Projected Shipments of Residential Oil-fired Hot Water Boilers in 

the Base Case and Each Standards Case.................................................. 9-B-10

Figure 9-B.3.3 Total Projected Shipments of Residential Oil-fired Steam Boilers in the 

Base Case and Each Standards Case........................................................ 9-B-11
9-B-1

APPENDIX 9-B. ADDITIONAL DATA ON SHIPMENTS OF RESIDENTIAL BOILERS

DOE used historical shipments data for domestic shipments and imports to populate its 

shipments model for residential boilers. The historical shipments data for all gas and oil boilers 

were collected from Appliance Magazine (AM), Air-Conditioning, Heating & Refrigeration Institute 

(AHRI),

a and the Energy Star program.2,3,4

9-B.1 HISTORICAL SHIPMENTS DATA

9-B.1.1 Appliance Magazine Shipment Data

DOE collected historical shipment data of total boilers (residential and commercial) 

disaggregated by fuel type from the Appliance Magazine as annual values for each year for the 

period 1960-19864,5,6 and 1990-20087,8

, as shown in Table 9-B.1.1.

Table 9-B.1.1 Historical shipments of boilers in the period 1960-1986 and 1990-2008.

Year Gas Boiler Oil Boiler Year Gas Boiler Oil Boiler

1960 141,700 141,400 1983 147,710 82,622

1961 155,300 144,900 1984 179,870 90,586

1962 161,800 136,300 1985 192,455 103,527

1963 170,100 152,100 1986 196,022 125,606

1964 199,600 165,500 1990 195,959 132,779

1965 200,300 184,000 1991 176,814 119,420

1966 186,500 149,000 1992 176,483 145,459

1967 173,800 149,000 1993 195,751 151,783

1968 186,800 147,083 1994 215,887 170,734

1969 175,800 135,228 1995 187,601 150,402

1970 163,800 156,521 1996 198,247 161,363

1971 157,200 141,670 1997 205,717 159,767

1972 155,700 167,220 1998 185,032 148,178

1973 146,700 151,657 1999 200,893 149,050

1974 122,600 90,961 2000 224,317 144,124

1975 88,100 98,921 2001 221,198 149,457

1976 112,600 132,271 2002 213,936 147,919

1977 112,900 134,200 2003 235,226 166,821

1978 126,100 108,046 2004 236,964 162,468

1979 221,300 85,059 2005 224,185 145,551

1980 293,300 51,672 2006 195,827 121,054

1981 161,600 67,492 2007 201,000 123,320

1982 147,600 72,822 2008 192,332 121,539

 

a AHRI is previously the Gas Appliance Manufacturers Association (GAMA)
9-B-2

9-B.1.2 AHRI Shipment Data

DOE collected historical shipment data of total boilers (residential and commercial) from 

AHRIb as annual values for each year for the period 1969-20002 and showed in Table 9-B.1.2.

Additionally, AHRI provided historical shipments information for the period of 2003 through 

2012; however, this set of information has not been disclosed for reasons of confidentiality.

Table 9-B.1.2 Historical shipments of boilers in the period 1969-2000.

Year Gas

Boiler

Oil

Boiler

Electric

Boiler Year GasBoiler

Oil

Boiler

Electric

Boiler

1969 175,800 1985 192,455 103,527

1970 163,800 1986 196,022 125,606 512

1971 157,200 1987 189,662 134,714 469

1972 155,700 134,273 1988 192,477 173,965 341

1973 146,700 130,302 1989 182,024 154,382

1974 122,600 90,961 3,654 1990 195,959 132,779 271

1975 88,100 98,921 1,689 1991 176,814 119,420 273

1976 112,600 132,271 1,597 1992 176,483 145,459 228

1977 113,100 134,200 2,154 1993 195,751 151,783 179

1978 125,900 108,046 1,950 1994 215,887 170,734 188

1979 221,300 85,059 2,724 1995 187,601 150,402 199

1980 293,300 51,672 2,660 1996 198,247 161,363 253

1981 161,600 67,492 1,735 1997 205,717 159,767

1982 147,600 72,822 808 1998 185,032 148,178

1983 147,700 82,622 663 1999 204,650 142,600

1984 179,870 90,586 634 2000 224,317 125,380

9-B.1.3 Energy Star Shipment Data

DOE collected historical shipments and market penetration data of residential boilers for

the period of 2003-2012 from the Energy Star program.

9 This information was used in a 

supplementary nature to expand upon the information provided by AHRI. For certain years, 

product types, and product classes, the Energy Star data was used to fill vacancies of the other 

data sets.

9-B.1.4 Summary of Historical Data by Product Class

DOE used the historical shipment data of total boilers from AHRI (some of which 

consisted of confidential data) and Appliance Magazine data, shown in Table 9-B.1.1 and Table 

9-B.1.2, as the annual shipment data for the period from 1960-2008. Once the total shipments by 

fuel type were establish, DOE disaggregated the shipments by hot water and steam boilers. See 

 

b Previously Gas Appliance Manufacturers Association (GAMA).
9-B-3

section B.1.4.2. The shipments of residential gas or oil boilers were calculated by multiplying the 

shipment of total boilers with the fractions of residential boilers in total boilers:

ShipRes,HW = ShipTot,HW * FracRes * FracHW

ShipRes,Steam = ShipTot,HW * FracRes * (1 - FracHW)

Eq. 9-B.1

Where:

ShipRes,HW = number of shipments of residential gas or oil hot water boilers,

ShipTot,HW = number of shipments of residential and commercial gas or oil boilers,

FracRes = the fraction of residential boilers in total shipped boilers, and

FracHW = the fraction of residential hot water boilers in total shipped boilers.

The AHRI and Appliance Magazine historical shipment data include some commercial 

sized boilers (>300 kBtu/h). To account for this, DOE determined the fraction of residential 

boilers compared from the total shipped boilers reported (FracRes). DOE derived FracRes based 

on the disaggregated 1993 shipment data by output capacity published in a PNNL report.1 DOE 

assumed that the shipment below 250 kBtu/h output capacity were residential boilers. The 

summary of the historical shipment of boilers is listed in Table 9-B.1.6.

Table 9-B.1.3 Historical shipments of residential boilers in 1993 1.

Output Capacity HWGB SGB HWOB SOB

<50 8,183 232 5 2

50-75 25,375 2,482 1,646 4

75-100 47,203 6,932 14,038 1,248

100-125 40,666 8,178 31,587 2,888

125-150 16,433 3,708 18,389 4,238

150-200 12,713 4,459 30,037 3,279

200-250 5,900 2,670 4,641 2,243

250-450 4,695 2,197 3,186 1,371

450-950 1,073 977 1,270 625

950-1500 256 431 628 451

>1500 179 487 1,101 723

Total 162,676 32,753 106,528 17,072

Fraction of Residential Boilers 96.2% 87.5% 94.2% 81.4%

9-B.1.4.2 Disaggregation of Hot Water and Steam Boilers

In order to derive the historical shipment by product class, DOE derived the fractions of 

hot water boilers in total boilers for the period of 1960-2011. Table 9-B.1.4 shows the shipment 

data collected from AHRI2 and the calculated fractions of hot water boilers’ shipment at 1970, 

1980, 1990, 1993, 2000. 
9-B-4

Table 9-B.1.4 Historical shipments data of hot water and steam boilers reported by 

AHRI.

Year

Shipments of Gas Boiler Shipments of Oil Boiler

Hot 

Water Steam Hot Water / Total Hot Water Steam Hot Water / Total

1970 90,474 15,663 85.2% 53,992 12,393 81.3%

1980 214,095 60,131 78.1% 32,065 11,697 73.3%

1990 151,167 33,711 81.8% 85,446 12,446 87.3%

1993 156,473 28,661 84.5% 100,343 13,902 87.8%

2000 176,444 36,904 82.7% 98,857 18,555 84.2%

Table 9-B.1.5 shows the shipment data collected from a PNNL report3 and the calculated 

fractions of hot water boilers’ shipment for the period of 2003-2007. 

Table 9-B.1.5 Historical shipments data of hot water and steam boilers reported from a 

PNNL report.

3

Year Shipments of Gas Boiler Shipments of Oil Boiler

Hot Water Steam Hot Water / Total Hot Water Steam Hot Water / Total

2003 186,627 38,105 83.0% 120,764 17,706 87.2%

2004 189,417 36,846 83.7% 133,288 19,460 87.3%

2005 179,717 37,127 82.9% 121,678 17,256 87.6%

2006 155,499 30,243 83.7% 99,801 16,016 86.2%

2007 147,873 33,932 81.3% 93,642 15,494 85.8%

The fractions of hot water boiler in other years between1970 and 2007 were interpolated

and the fractions of hot water boilers before 1970 are assumed the same value with 1970. The 

fractions of hot water boilers after 2007 are calculated using the 5-year average values of 

fractions between 2003 and 2007. The disaggregated historical shipments by product classes are 

shown in Table 9-B.1.6.

Table 9-B.1.6 Historical Shipment Data of Boilers

Shipments Data Fractions of

Hot Water Boilers Calculated Shipments

Year Gas

Boiler

Oil

Boiler

Electric

Boiler

Gas

Boiler

Oil

Boiler HWGB SGB HWOB SOB

1960 141,700 141,400 83.8% 80.0% 114,457 22,205 107,638 26,872

1961 155,300 144,900 83.8% 80.0% 125,442 24,337 110,302 27,537

1962 161,800 136,300 83.8% 80.0% 130,693 25,355 103,756 25,902

1963 170,100 152,100 83.8% 80.0% 137,397 26,656 115,783 28,905

1964 199,600 165,500 83.8% 80.0% 161,225 31,279 125,984 31,451

1965 200,300 184,000 83.8% 80.0% 161,791 31,389 140,067 34,967

1966 186,500 149,000 83.8% 80.0% 150,644 29,226 113,424 28,316

1967 173,800 149,000 83.8% 80.0% 140,386 27,236 113,424 28,316

1968 186,800 147,083 83.8% 80.0% 150,886 29,273 111,964 27,952
9-B-5

1969 175,800 135,228 83.8% 80.0% 142,001 27,549 102,940 25,699

1970 163,800 156,521 83.8% 80.0% 132,308 25,669 119,149 29,745

1971 157,200 141,670 83.1% 79.3% 125,956 25,656 106,822 27,945

1972 155,700 167,220 82.4% 78.5% 123,742 26,422 124,881 34,190

1973 146,700 151,657 81.7% 77.7% 115,637 25,848 112,165 32,102

1974 122,600 90,961 3,654 81.1% 77.0% 95,843 22,398 66,618 19,910

1975 88,100 98,921 1,689 80.4% 76.2% 68,300 16,668 71,735 22,366

1976 112,600 132,271 1,597 79.7% 75.5% 86,563 22,035 94,965 30,860

1977 112,900 134,200 2,154 79.0% 74.7% 86,060 22,827 95,382 32,278

1978 126,100 108,046 1,950 78.4% 74.0% 95,302 26,315 76,014 26,767

1979 221,300 85,059 2,724 77.7% 73.2% 165,814 47,619 59,229 21,685

1980 293,300 51,672 2,660 77.0% 72.4% 217,856 65,017 35,608 13,546

1981 161,600 67,492 1,735 77.4% 73.8% 120,685 35,170 47,401 16,802

1982 147,600 72,822 808 77.9% 75.2% 110,826 31,527 52,107 17,167

1983 147,710 82,622 663 78.3% 76.6% 111,505 30,953 60,211 18,385

1984 179,870 90,586 634 78.7% 78.0% 136,509 36,966 67,211 18,961

1985 192,455 103,527 79.1% 79.4% 146,838 38,775 78,181 20,301

1986 196,022 125,606 512 79.5% 80.8% 150,352 38,702 96,514 22,972

1987 189,662 134,714 469 79.9% 82.2% 146,240 36,680 105,292 22,858

1988 192,477 173,965 341 80.4% 83.6% 149,188 36,447 138,269 27,219

1989 182,024 154,382 80.8% 84.9% 141,821 33,732 124,744 22,115

1990 195,959 132,779 271 81.2% 86.3% 153,470 35,523 109,042 17,267

1991 176,814 119,420 273 82.1% 86.6% 140,026 30,503 98,380 15,221

1992 176,483 145,459 228 83.0% 86.9% 141,310 28,899 120,207 18,164

1993 195,751 151,783 179 83.9% 87.1% 158,454 30,338 125,825 18,562

1994 215,887 170,734 188 83.7% 86.8% 174,267 33,945 140,917 21,497

1995 187,601 150,402 199 83.5% 86.4% 151,012 29,920 123,593 19,480

1996 198,247 161,363 253 83.2% 86.0% 159,135 32,064 132,017 21,483

1997 205,717 159,767 83.0% 85.6% 164,668 33,736 130,133 21,848

1998 185,032 148,178 82.8% 85.2% 147,694 30,760 120,158 20,799

1999 200,893 149,050 82.5% 84.9% 159,902 33,849 120,327 21,460

2000 224,317 144,124 82.3% 84.5% 178,041 38,301 115,829 21,272

2001 221,198 149,457 82.5% 85.4% 176,098 37,237 121,408 20,766

2002 213,936 147,919 82.8% 86.3% 170,831 35,500 121,439 19,272

2003 235,226 166,821 83.0% 87.2% 188,397 38,466 138,400 20,292

2004 236,964 162,468 83.7% 87.3% 191,323 37,217 134,861 19,690

2005 224,185 145,551 82.9% 87.6% 179,196 37,019 121,262 17,197

2006 195,827 121,054 83.7% 86.2% 158,114 30,752 99,231 15,924

2007 201,000 123,320 81.3% 85.8% 157,674 36,181 100,656 16,655

2008 192,332 121,539 82.9% 86.8% 150,491 31,410 98,236 14,045

Data from GAMA 2001

Data from both GAMA 2001 and Appliance Magazine 2000

Data from Appliance magazine, 2000 + 2011

The fraction of residential boilers’ shipment in total boilers’ shipment1

Fraction calculated based on historical GAMA data2

Fraction calculated based on Science Applications International Corp. report(2009)3

Interpolated fraction
9-B-6

To account for the fraction of shipments from non-AHRI member companies, DOE 

applied an adjustment factor to each year of the historical shipments. This adjustment factor was 

developed by comparing of the model information from 2012 CEC, NRCAN, and Energy Star 

directories to that of the AHRI reported values. Considering that the AM and GAMA data do not 

include tube/coil boilers and steel boilers, DOE estimated that the ratio of tube/coil boiler to cast 

iron boiler is 7.2% for gas-fired boilers and the ratio of steel boiler to cast iron boiler is 0.1% for 

gas-fired boilers and 14.2% for oil-fired boiler. DOE also estimated that the fraction of electric 

hot water boilers is 3.4% and fraction of electric steam boilers is the same with gas-fired and oilfired steam boilers based on the boiler units information derived from Energy Information 

Administration’s 2009 Residential Energy Consumption Survey (RECS 2009)8 and Energy 

Information Administration’s 2003 Commercial Buildings Energy Consumption Survey (CBECS 

2003).

9 The adjusted historical shipments by product classes are shown in Table 9-B.1.7

Table 9-B.1.7 Adjusted Historical Shipment Data of Boilers

Year HWGB SGB HWOB SOB EHWB ESB

1960 113,719 29,051 107,984 32,009 7,658 1,956 

1961 124,634 31,839 110,657 32,801 8,123 2,075 

1962 129,850 33,171 104,090 30,854 8,069 2,061 

1963 136,511 34,873 116,156 34,431 8,720 2,227 

1964 160,186 40,921 126,389 37,464 9,884 2,525 

1965 160,748 41,065 140,517 41,652 10,399 2,656 

1966 149,673 38,235 113,788 33,729 9,084 2,321 

1967 139,481 35,632 113,788 33,729 8,737 2,232 

1968 149,914 38,297 112,324 33,295 9,041 2,310 

1969 141,086 36,042 103,271 30,612 8,423 2,152 

1970 131,455 33,582 119,532 35,432 8,666 2,214 

1971 126,159 32,228 108,191 32,070 8,088 2,066 

1972 124,955 31,921 127,703 37,854 8,732 2,231 

1973 117,732 30,076 115,817 34,331 8,069 2,061 

1974 98,391 25,135 69,465 20,591 5,784 1,478 

1975 70,703 18,062 75,544 22,393 5,056 1,292 

1976 90,366 23,085 101,013 29,942 6,619 1,691 

1977 90,606 23,146 102,486 30,379 6,679 1,706 

1978 101,200 25,852 82,513 24,458 6,338 1,619 

1979 177,601 45,370 64,958 19,255 8,319 2,125 

1980 235,677 60,131 36,617 11,697 9,322 2,378 

1981 131,064 32,597 52,810 14,383 6,286 1,563 

1982 120,822 29,287 58,362 14,553 6,103 1,479 

1983 122,181 28,821 67,801 15,416 6,443 1,520 

1984 150,152 34,503 76,093 15,700 7,643 1,756 

1985 162,129 36,282 88,993 16,570 8,445 1,890 

1986 166,840 36,308 110,459 18,438 9,272 2,018 

1987 162,891 34,504 121,163 17,988 9,442 2,000 

1988 166,801 34,382 159,982 20,921 10,771 2,220 

1989 159,161 31,914 145,124 16,519 9,989 2,003 

1990 173,082 33,711 120,970 12,446 9,681 1,886 

1991 158,517 28,908 115,829 11,108 9,040 1,649 
9-B-7

1992 160,574 27,347 142,439 13,427 9,988 1,701 

1993 181,143 28,661 141,822 13,902 10,730 1,698 

1994 200,605 32,167 169,145 16,544 12,262 1,966 

1995 175,041 28,438 149,309 15,372 10,768 1,749 

1996 185,736 30,564 160,690 17,349 11,513 1,895 

1997 193,524 32,248 159,403 18,025 11,751 1,958 

1998 174,776 29,484 148,110 17,504 10,760 1,815 

1999 190,530 32,531 149,240 18,398 11,347 1,937 

2000 213,366 36,904 135,650 18,555 11,724 2,028 

2001 212,234 36,205 152,343 18,115 12,167 2,076 

2002 214,286 34,836 153,567 16,814 12,269 1,994 

2003 239,843 38,105 169,680 17,706 13,652 2,169 

2004 264,588 36,846 167,444 19,460 14,574 2,030 

2005 252,465 37,127 152,742 17,256 13,623 2,003 

2006 229,231 30,243 127,531 16,016 12,106 1,597 

2007 232,969 33,932 130,301 15,494 12,248 1,784 

2008 259,742 32,374 132,785 11,061 13,180 1,643 

2009 204,370 23,540 98,626 9,616 10,249 1,181 

2010 208,711 21,957 106,340 9,951 10,674 1,123 

2011 218,112 25,615 99,611 9,084 10,723 1,259 

2012 246,590 28,516 84,952 7,483 11,201 1,295 

9-B.2 FRACTION OF RESIDENTIAL BOILERS SHIPPED TO COMMERCIAL 

BUILDINGS

DOE derived residential boiler shipments by building types from the Energy Information 

Administration’s (EIA) 2009 Residential Energy Consumption Survey (RECS 2009) and Energy 

Information Administration’s 2003 Commercial Buildings Energy Consumption Survey (CBECS 

2003)10 data. DOE assumed that boilers in residential and commercial buildings smaller than 

10,000 sq. ft. are residential boilers and two boilers are used per commercial building. Table 9-

B.2.1 summarizes the shipments of residential boilers by building types. As can be seen from the 

table, 7% of gas boilers and 7% of oil boilers were shipped to the commercial sector.
9-B-8

Table 9-B.2.1 Residential Boilers’ Shipments by Building Types

Building Type Description Buildings < 10,000 sqft

Units Frac

Gas Boilers

Single-Family (Unshared) 3,123,528 64%

Multi-Family Units (Unshared) 948,223 19%

Single-Family (Shared) 100,716 2%

Multi-Family Bldgs - 2-4 Units (Shared) 244,365 5%

Multi-Family Bldgs - 5+ Units (Shared) 112,388 2%

Commercial (2 boilers per bldg.) 336,350 7%

Gas Boilers Total 4,865,570 100%

Oil Boilers

Single-Family (Unshared) 2,439,082 82%

Multi-Family Units (Unshared) 184,548 6%

Single-Family (Shared) 29,843 1%

Multi-Family Bldgs - 2-4 Units (Shared) 84,220 3%

Multi-Family Bldgs - 5+ Units (Shared) 27,923 1%

Commercial (2 boilers per bldg.) 198,362 7%

Oil Boilers Total 2,963,978 100%

9-B.3 PROJECTED SHIPMENTS BY PRODUCT CLASSES

Figure 9-B.3.1 to Figure 9-B.3.3 show total projected shipments of gas-fired steam 

boilers, oil-fired hot water boilers and oil-fired steam boilers in the base case and under each 

standards case, respectively. Because the elasticity is modeled as a delayed replacement of a 

boiler, the projection for the standards case shows a decline in the early years, but an increase in 

later years once the delayed replacements are finally made. Recall that the elasticity parameter 

decreases over time, so the impact of the standards on shipments diminishes.
9-B-9

Figure 9-B.3.1 Total Projected Shipments of Residential Gas-fired Steam Boilers in the 

Base Case and Each Standards Case
9-B-10

Figure 9-B.3.2 Total Projected Shipments of Residential Oil-fired Hot Water Boilers in the 

Base Case and Each Standards Case
9-B-11

Figure 9-B.3.3 Total Projected Shipments of Residential Oil-fired Steam Boilers in the Base 

Case and Each Standards Case
9-B-12

REFERENCES

1. Richman, E. E., Current and Projected Commercial Space Heating, Space Cooling, and 

Water Heating Equipment Use in the United States: Update 1995, January, 1995. Pacific 

Northwest Laboratory. Richland, WA. 

2. Kendall, M., Comment #24 on the Efficiency Standards for Furnaces and Boilers (GAMA 

Shipment Data) Docket No. EE-RM/STD-01-350, April 10, 2002. Gas Appliance 

Manufacturers Association. Arlington, VA. 

3. Science Applications International Corporation, Development of Issues Papers for GHG 

Reduction Project Types: Boiler Efficiency Projects, Table 2, January 7, 2009. 

<http://www.climateactionreserve.org/wp-content/uploads/2009/03/future-protocoldevelopment_boiler-efficiency.pdf>

4. U.S. Appliance Industry Statistical Review. Appliance Magazine, 1970: pp. 53. 

5. U.S. Appliance Industry Statistical Review. Appliance Magazine, 1979: pp. 41. 

6. U.S. Appliance Industry Statistical Review. Appliance Magazine, 1987. 

7. U.S. Appliance Industry Statistical Review. Appliance Magazine, 2000. 

8. U.S. Appliance Industry Statistical Review. Appliance Magazine, 2009. 

9. U.S. Environmental Protection Agency: ENERGY STAR, Unit Shipment Data Archives, 

(Last accessed September, 2013.) 

<http://www.energystar.gov/index.cfm?c=partners.unit_shipment_data_archives>

10. U.S. Department of Energy - Energy Information Administration, Commercial Buildings 

Energy Consumption Survey, 2003. (Last accessed November, 2010.) 

<http://www.eia.doe.gov/emeu/cbecs/>