Nearly all heat transfer systems can be reversed, providing central cooling as well as heating. Some heat pumps and most GeoExchange SM systems also provide domestic hot water at low operating costs. Heat Pumps Beginning in the 1970s, air-source heat pumps came into common use. They have the advantage of no combustion, and thus no possibility of indoor pollutants like carbon monoxide. Heat pumps provide central air conditioning as well as heating as a matter of course.
Heat pumps operate by moving or transferring heat, rather than creating it.
During the summer, a heat pump captures heat from inside a home or business and transfers it to the outdoor air through a condensing unit. During the winter, the process is reversed. Heat is captured from outdoor air, compressed, and released inside. Much less electricity is used to move heat rather than create it, making heat pumps more economical than resistance heating. However, in all but the most moderate climates, the heating ability of the heat pump is limited by freezing outdoor temperatures.