NFU Energy guide to heat pumps
All air conditioners and refrigeration systems are heat pumps. They absorb heat into a refrigerant gas in the evaporator (the cold side of the heat pump) and release the heat from the condenser (the hot side of the heat pump). Most heat pumps use a refrigerant, which is pumped around a system of pipework from a heat source (air, water, or ground), to the area where heat is required.