Heat pumps can provide a home with both heating and cooling. By using electricity to move heat from a cool space into a warm, heat pumps make the cool space cooler and the warm space warmer. As Energy Savers puts it, "during the heating season, heat pumps move heat from the cool outdoors into your warm house; during the cooling season, heat pumps move heat from your cool house into the warm outdoors. Because they move heat rather than generate heat, heat pumps can provide up to 4 times the amount of energy they consume." Consumers who heat with electricity have found that they can save a lot of money by adding a heat pump to use their heated air more effectively.
There are several varieties of heat pumps on the market. Air-source heat pumps, the most common type, have been used most efficiently in moderate to warm climates, but new models are claiming to work well in cold climates. The ductless, "mini-split", popular in Europe and Asiai, is expensive, but small. easily installed and very flexible. It can be used to heat and cool a new room addition, to provide ductless air conditioning and/or additional heat in a home with an unducted (i.e., boiler) system, or as part of a "zoned" heating and cooling system. The dual-fuel heat pump system combines a heat pump with a gas furnace, which adds more warmth in really cold weather. Electicity powers the system in more moderate cold and in hot weather. Geothermal heat pumps don't move the outside air temperature, but instead use a loop of underground piping to tap the relatively constant temperature of the earth, then feed it through a "ground heat exchanger" into a ducted, air source heat pump for distribution. Such a system is expensive to install, but once in place is very efficient in all climates, easy to maintain, long-lasting and fuel-free. An interesting system now in development, the absorption heat pump, or GAX, is discussed in "Go Deeper."