Air source heat pumps use considerably less energy than conventional electric water heaters by taking heat from the surrounding air and boosting it to a much higher temperature. Air-to-water heat pumps can considerably reduce the energy usage of your hot tub or spa due to their high COP (Coefficient of Performance). If a unit has a COP of 12, this means that it is capable of producing 12kW of heat energy for every 1kW of electricity it consumes.