Overall efficiency depends on several factors. Not least, heat pump model, property insulation and outdoor temperatures. Most of the Air-to-Air heat pumps have efficiencies of around 400% when properly installed.

In simple terms even when temperatures drop below 0 °C there is a lot of energy in the air. In fact until −273.15 °C (absolute zero) air contain energy ripe to be extracted. This energy stolen from outside, account for the efficiencies above 100%.

An Air Source heat pump uses refrigerant gases to move and concentrate the energy found in the air.

Air to Air Heatpumps push warm or cool air into a room, depending on the desired setting. They are identical to Air Conditioning but instead of only operating in cooling mode, they are able to operate in heating mode too.

Air to Water Heatpumps utilize the same technological principles but instead of directly heating the air in a room, they heat water which can then be pushed through radiators or through hot water systems for washing. Whilst some are also capable of cooling, they tend to do so with less efficacy than Air to Air Heatpumps.