The average air temperature throughout the UK is around 7°C. Air source heat pumps work by converting the solar energy stored in the surrounding air into useful heat. The heat is picked up out of the surrounding atmosphere and is transferred to either an air or water based heating system. Air is an inexhaustible source of energy and therefore a sustainable solution for the future.
Air source heat pumps look similar to a large fan. They draw in the surrounding air over the evaporator where the heat is extracted/used. With the heat removed, colder air is then vented away from the unit. An air source heat pump is slightly less efficient than a ground source mainly because of the fluctuating temperature in the atmosphere, compared to the more stable conditions in the ground. However, the installation of these units is less expensive. As with all heat pumps, air source models are most efficient at producing low temperatures for distribution systems such as underfloor heating.
Their efficiency is helped by a higher ambient temperature, however, an air source heat pump will also work in temperatures below 0°C and are capable of operating to temperatures as low as -20°C, although the colder the temperature the less efficient the heat pump becomes. The efficiency of an air source heat pump is rated as COP (Coefficient of Performance). The COP is calculated by dividing the useful heat output by the energy input which is usually rated at around 3.