This system gets its name from the way it uses the difference between the outdoor air temperature and the indoor air temperature to heat or cool a home. During the summer, the air source heat pump functions as an air conditioner; during the winter, it runs in reverse to provide heat. Properly installed and connected to a well-designed (and tight) duct system, an air source heat pump can deliver up to three units of heating (or cooling) energy for every unit of electric energy it consumes except in very cold weather, when a backup resistance heating system must supplement the heat pump’s output.
Because it heats and cools, an air source heat pump is a good choice for replacing an existing heating and cooling system or when you need a new furnace and want to add central air-conditioning. Look for a heat pump with a high HSPF and SEER rating. The best units have a two-stage compressor that runs in a low-power, energy-saving mode most of the time, along with a variable speed blower motor that minimizes noise and energy consumption.