 The COP for heat pumps range from 3.2 to 4.5 for air source heat pumps to 4.2 to 5.2 for ground source heat pumps.When used for heating a building with an outside temperature of, for example, 10 °C, a typical air-source heat pump (ASHP) has a COP of 3 to 4, whereas an electrical resistance heater has a COP of 1.0.That is, to produce one joule of useful heat, a resistance heater needs one joule of electrical energy, while a heat pump under conditions where its COP is 3 or 4 would require only a 0.33 or 0.25 joules of electrical energy, the difference being taken from the cooler place.