The coefficent of performance (also known as COP) specifies the ratio between the energy transfer of a heating pump and the total input of electrical energy. COP is a dimensionless number that expresses the efficiency of a heating system -- a pump with a higher COP transfers more heat with an equivalent energy input. You can precisely calculate a heating pump's COP if you know the input energy and output heat. You can estimate the COP if you know the heat pump refrigerant's properties.
Calculate the heat output of the heating pump in BTUs per hour (a BTU is the amount of energy required to heat a pound of water 1 degree Fahrenheit and is equal to approximately 1.055 kilojoules).
Divide the heat output by the total energy input of the heating pump in kilowatts (a kilowatt is equal to 1000 watts).
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Divide your result by the conversion constant of 3,413 to find the coefficient of performance of the pump.
Add 460 to the temperature at which the refrigerant in the heating pump evaporates.
Divide this number by the difference between the refrigerant's condensation and evaporation temperatures.
Multiply this number by 0.6 to find the heating pump's approximate coefficient of performance.