Coefficient of performance or COP of a heat pump is a ratio of useful heating provided relative to energy used. Higher COPs equate to higher efficiency, lower energy (power) consumption and thus lower operating costs.

The COP usually exceeds 1, especially in heat pumps, because instead of just converting work to heat (which, if 100% efficient, would be a COP of 1), it pumps additional heat from a heat source to where the heat is required. Less work is required to move heat than for conversion into heat, and because of this, heat pumps, air conditioners and refrigeration systems can have a coefficient of performance greater than one.