Coefficient of Performance

The ratio of cooling or heating to energy consumption.

for heat pumps


for refrigerators and air conditioners:



QH = Heat In

QL = Rejected Heat

Typical values for COP are in the range 2-4. The energy output exceeds the input, because the system takes advantage of the heat released or absorbed by the refrigerant when it condenses or evaporates.

A heat pump that delivers two units of cooling for each unit of electricity also rejects three units of heat. This then gives it a COP of 2.0 for cooling and a COP of 3.0 for heating.

The upper limit of COP is based on reversed Carnot Cycle:

Heat pumps:

COPc = TH /(TH - TL)


COPc = TL /(TH - TL)

See also: Cooling Efficiency, Heat Pump, Power, Thermoelectric Cooling.

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Subjects: Heating Ventilation and Air Conditioning Thermodynamics