Two main types of heat pumps are used in residential and commercial applications: air-source heat pumps (by far the most common) and ground-source (or geothermal) heat pumps. A heat pump works like an air conditioner in the cooling cycle; in the heating cycle, it simply works in reverse (i.e. cooling the outside, and venting heat to the inside). Ground-source heat pumps transfer heat through earth or water, whereas air-source heat pumps do so via air. Because heat pumps simply move heat around rather than creating heat, they can be a very efficient method of space conditioning, especially in moderate climates.
Heat pump efficiency is rated using two metrics: SEER (Seasonal Energy Efficiency Ratio) is used to rate the performance when the unit is acting as an air conditioner; HSPF (Heating Seasonal Performance Factor) is used to rate the performance when the unit is in heating mode.
Research, policies, and programs related to heat pump efficiency can be found in the links below and to the right. For specific efficiency tips and guidance on heat pumps, click here.