Heat pumps are put to use to deliver heating because less high grade power is needed for their function than appears in the discharged heat. A lot of the power for heating stems from the external environment, and only a fraction stems from electricity (or some other high grade energy source required to operate a compressor). In electrically powered heat pumps, the heat transferred can be three or 4 times bigger than the electrical power used, giving the system a coefficient of performance (COP) of 3 or 4, as opposed to a COP of 1 for a ordinary electrical resistance heating u