Air source heat pumps work by converting the energy of the outside air into heat. They supply a comfortable temperature inside the house as well as energy for the hot water system. As with all heat pumps, air source models are most efficient when supplying low temperature systems such as underfloor heating.
When properly sized, the heat pump should be able to supply all of the space and hot water heating to the house. Generally these systems will produce 4 times as much energy as you use, giving you a huge energy and carbon saving.
Air source heat pumps are reported to be less efficient than geothermal systems but they can be ideal for houses and apartments where outside space is limited. There are also lower installation costs and less disruption.