Water Heater Energy Factor

The energy factor for gas-fired and electric storage water heaters is a derived shipment-weighted efficiency based on the year the equipment was purchased (Table 12). This number is the average efficiency for all units sold within a particular year weighted by the number of units in each efficiency bin (GAMA 1996). For LPG-fired water heaters, we assumed the same energy factor as for natural gas-fired units. For fuel oil-fired units, we assumed an energy factor of 0.54 before 1990 and 0.59 after 1990 (Lutz, personal communication).

For instantaneous water heaters the energy factor will be determined by de-rating the  efficiency by 7% from manufacturer's data [1]

Table 12. Shipment Weighted Energy Factors for Storage Water Heaters

Year

Electric

Natural Gas

LPG

Fuel Oil

1972

0.798

0.474

0.474

0.54

1973

0.798

0.474

0.474

0.54

1974

0.798

0.474

0.474

0.54

1975

0.798

0.474

0.474

0.54

1976

0.799

0.475

0.475

0.54

1977

0.799

0.475

0.475

0.54

1978

0.8

0.476

0.476

0.54

1979

0.801

0.476

0.476

0.54

1980

0.802

0.477

0.477

0.54

1981

0.803

0.478

0.478

0.54

1982

0.804

0.479

0.479

0.54

1983

0.806

0.48

0.48

0.54

1984

0.809

0.481

0.481

0.54

1985

0.812

0.483

0.483

0.54

1986

0.815

0.484

0.484

0.54

1987

0.819

0.486

0.486

0.54

1988

0.823

0.488

0.488

0.54

1989

0.828

0.49

0.49

0.54

1990

0.832

0.492

0.492

0.59

1991

0.837

0.494

0.494

0.59

1992

0.842

0.496

0.496

0.59

1993

0.846

0.498

0.498

0.59

1994

0.85

0.499

0.499

0.59

1995

0.854

0.5

0.5

0.59

1996

0.857

0.501

0.501

0.59

1997

0.857

0.501

0.501

0.59

1998

0.857

0.501

0.501

0.59

1999

0.857

0.501

0.501

0.59

2000

0.857

0.501

0.501

0.59

2001

0.857

0.501

0.501

0.59

2002

0.857

0.501

0.501

0.59

2003

0.857

0.501

0.501

0.59

2004

0.9

0.55

0.55

0.59

2005

0.9

0.55

0.55

0.59

Source: GAMA Directory.

Note: Energy Factor for Water Heaters is percentage efficiency divided by 100.

Note: yellow cells contain data held constant from previous real data point.

Note: In 2004, a new standard for water heaters went into effect (green cells).

[1] Reference: http://fsec.ucf.edu/en/publications/pdf/FSEC-CR-1856-10.pdf, (see Fig E-4)


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