Air Source Heat Pumps collects thermal energy from the outside air. The heat pump is located externally, either next to an outside wall, or connected to the property with pre-insulated pipes buried in a trench. The main internally located items are the hot water cylinder, a buffer tank and two expansion vessels.

As with all types of heat pumps, it is important to specify the right size (kW) heat pump. For this a room by room heat loss assessment of the property is required. A heat pump produces less hot water than a boiler and the lower temperature it can operate at, the more efficient the system is. Therefore, the overall efficiency of the heating system requires heating distribution (underfloor heating, radiators or fan coil units) which can deliver comfortable room temperatures at low operating temperatures.