Heat Pumps Performance and Efficiency Ratings

Rating performance and efficiency of heat pumps

Several methods are used to rate heat pump performance and efficiency

COP - Coefficient of Performance

The Coefficient of Performance - COP - is the ratio of heat output to the amount of energy input of a heat pump.

cop heat pump efficiency

COP can be expressed as

COP = hh / hw         (1)

where

COP = Coefficient of Performance

hh = heat produced (Btu/h)

hw = equivalent electric energy input (Btu/h) = 3413 Pw

where

Pw = electrical input energy (W)

If a heat pump delivers 3 units of heat for every unit of energy input - the COP is 3.

  • 1 kW = 1000 W = 3413 Btu/h

Example - COP Heat Pump

Cooling Cycle

A heat pump delivering 60000 Btu/h with a total input of 9 kW:

COP = (60000 Btu/h) / (3413 (9 kW))

       = 1.95

Heating Cycle 

A heat pump delivering 50000 Btu/h with a total input of 7 kW:

COP = (50000 Btu/h) / (3413 (7 kW))

       = 2.1

EER - Energy Efficiency Ratio

The Energy Efficiency Ratio - EER - measures the cooling efficiency of a heat pump.

EER can be expressed as

EER = hc / Pw         (2)

where

EER = Energy Efficiency Rating

hc = cooling heat (Btu/h)

Pw = electrical power (W)

Example - EER

An air conditioner or heat pump in cooling modus draws 1000 W to produce 10000 Btu/h cooling. The EER can be calculated as

EER = (10000 Btu/h) / (1000 W)

    = 10

HSPF - Heating Season Performance Factor

The Heating Season Performance Factor - HSPF - is a measure of the overall heating efficiency of a heat pump during a season.

HSPF = hs / 1000 Pws     (3)

where 

hs = heat produced during the season (Btu)

Pws = electrical power consumed during the season (kWh)

The HSPF can be regarded as an "average" COP for an entire heating season. It is common to compare BTUs of heat output to watts of electrical energy input. HSPF of 6.8 can be compared with an average COP of 2 and a HSPF in the range of 5-7 is acceptable.

Example - Heat Pump Heating Season Performance Factor

For a heat pump delivering 120,000,000 Btu during the season when consuming 15,000 kWh the HSPF can be calculated as 

HSPF = (120000000 Btu) / (1000 (15000 kWh))

       = 8

SEER - Seasonal Energy Efficiency Ratio

Seasonal Energy Efficiency Ratio is a measure of the seasonal cooling efficiency of a heat pump or a consumer central air conditioning system.

The SEER should be at least 13 to be sold in the United States. SEER above 20 is a very efficient system.

Related Topics

  • Air Conditioning - Air Conditioning systems - heating, cooling and dehumidification of indoor air for thermal comfort
  • Heating - Heating systems - capacity and design of boilers, pipelines, heat exchangers, expansion systems and more

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