Is an air-source heat pump a viable option?
Air-source is much easier and cheaper to install compared to other types of heat pumps, but it does not promise very high energy efficiencies for year-round heating in cold climates. The main reason is that the efficiency drops when you need most heat. A back-up from a boiler at such times is usually required. Ground source, by contrast, maintains a constant heat output unaffected by the daily temperature changes above. Smaller air systems may give reasonable overall results if used alongside a boiler, but only if used when air temperatures are not too cold. Air source units usually have a shorter life since they have to work out in the elements.
