A form of mechanical heating and cooling that utilizes a circulating refrigerant to remove and reject heat. In heating mode, the heat pump removes heat from outside and rejects it into the structure to increase the temperature of the space. In cooling mode, the heat pump removes heat from inside the structure and rejects it outside to decrease the temperature of the space.
Heat pump technology has come a long way since first invented. Newer-style heat pumps have high energy conservation ratings and can operate efficiently even at really cold outside temperatures.