# Heat Pumps - Performance and Efficiency Ratings

## Rating the performance and efficiency of heat pumps

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Several methods can be 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* for a heat pump.

COP can be expressed as

COP = h_{h}/ h_{w}(1)

where

COP = Coefficient of Performance

h_{h}= heat produced (Btu/h)

h_{w}= equivalent electric energy input (Btu/h) = 3413 P_{w}

where

P_{w}= 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 deliver *60000 Btu/h* with a total electric input of *9 kW*:

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

* = 1.95*

##### Heating Cycle

A heat pump deliver *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* - is a measure of the cooling efficiency of a heat pump.

EER can be expressed as

EER = h_{c}/ P_{w}(2)

where

EER = Energy Efficiency Rating

h_{c}= cooling heat (Btu/h)

P_{w}= electrical power (W)

#### Example - EER

An air conditioner or heat pump in cooling mode draws *1000 W* of electric power to produce *10000 Btu/h* of 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 the season.

*HSPF = h*_{s}* / 1000 P*_{ws }* (3)*

*where *

*h*_{s}* = heat produced during the season (Btu)*

*P*_{ws}* = 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. *A HSPF in the range of *5-7* is acceptable.

#### Example - Heat Pump Heating Season Performance Factor

For a heat pump deliver *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.

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