Air Source Heat Pump (ASHP) is a system that transfers heat from outside to inside a building, or vice versa. Under the principles of vapour 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, in 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 source heat pumps can provide fairly low cost space heating. A high efficiency heat pump can provide up to four times as much heat as an electric heater using the same energy, in comparison to gas as a primary heat source. A “standard” domestic air source heat pump can extract useful heat down to about -5F or 0F (-18C).