Air Source Heat Pumps extract heat from the outside air by drawing it in and compressing it, in the same way that a fridge extracts heat from it's interior. Heat can be extracted even when the outside temperature drops as low as minus 15°C.

There are two main types: Air-to-water and
Air-to-Air systems. Air-to-water uses the heat to warm water. As the water is heated to a much lower temperature than standard boilers, they tend to be used for underfloor heating systems rather than radiators. Air-to-Air produces warm air, circulated by fans to heat your home.