Air source heating appliances utilize the air in the atmosphere for space heating and domestic hot water. Useful heat can be obtained from air in the atmosphere as low as -15 degrees C. Air source heating appliances as it's description says, utilizes air as the energy source, which passes over a heat exchanger to capture the heat in the air, then using compression technology, the heat is upgraded to a higher temperature that is useful for space heating and domestic hot water when connected to a water cylinder.
Air source heating appliances are ideal for use with underfloor heating systems due to the lower temperatures required, which is approx 40 degrees C, the heat generated can also be passed into a water cylinder to help heat domestic hot water.
Air source heating appliances are usually situated outside a property; they lend themselves well to existing and new build properties due to a minimal installation preparation, which predominantly entails ensuring a flat and stable foundation. Air source heating appliances are also quite often used to heat swimming pools.
Air source heating appliances run off of a low amount of electricity in comparison to the energy return, the measure of the energy input versus the energy output is called a Coefficient of Performance and is usually shown as a ratio, for example 1:3.9 which is 1kW electricity used to generate 3.9kW of heat generated. Air source heating appliances can achieve varying performances, and will often quote the Coefficient of Performance which can be used to compare different brands of Air source heating appliances.