Literally, a device that pumps heat energy. Heat pumps are used in both heating and cooling systems. They are most commonly used as summer air conditioners in warm climates, but if the pumping process is reversed they can be used as cold-weather heating units. Heat pumps operate on the principle that all naturally-occurring air contains heat energy. Using basic principles of refrigeration, heat pumps extract heat energy from the air and dissipate it elsewhere. When used as heating units, heat pumps are able extract heat energy from even the coldest outdoor air to heat the inside of a structure. When used as cooling units, they can extract heat from indoor air even if the outdoor air is much hotter.

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