Energy can exist around us in the form of heat, light, mechanical, electrical or chemical energy, and although energy can neither be created nor destroyed, it can be changed from one form to another and moved from place to place. A heat pump derives its name from its ability to "pump" or move heat from one area to another.

Heat pumps do not produce energy by themselves any more than a well water pump can produce water by itself. The well pump needs to be attached to a source of water before it can pump any water. Similarly a heat pump will not produce any heat if not connected to an energy source such as the earth; however, if an energy source is available and the heat pump is able to tap it then vast amounts of energy can be moved at very little cost.