Air source heat pumps

An air source heat pump (ASHP) is a system which transfers heat from outside to inside a building, or vice versa. Under the principles of vapor compression refrigeration, an ASHP uses a refrigerant system involving a compressor and a condenser to absorb heat at one place and release it at another. They can be used as a space heater or cooler, and are sometimes called 'reverse-cycle air conditioners'. In domestic heating use, an ASHP absorbs heat from outside air and releases it inside the building, as hot air, hot water-filled radiators, underfloor heating and/or domestic hot water supply. The same system can often do the reverse in summer, cooling the inside of the house. When correctly specified, an ASHP can offer a full central heating solution and domestic hot water up to 80 °C. Air at any temperature above absolute zero contains some energy. An air-source heat pump transfers ('pumps') some of this energy as heat from one place to another, for example between the outside and inside of a building. This can provide space heating and/or hot water. A single system can be designed to transfer heat in either direction, to heat or cool the interior of the building in winter and summer respectively. For simplicity, the description below focuses on use for interior heating.