Unlike most heating equipment that burns fuel to create warmth, heat pumps use a vapor-compression cycle to move heat from one place to another. In winter, heat is extracted from the air or the ground, concentrated, and distributed inside via air ducts or radiant-floor tubing. In summer, the same equipment runs in reverse to remove heat from indoor air and dump it outside. In this article, contributing writer Scott Gibson takes a look at both air-source (ASHPs) and ground-source, or geothermal, heat pumps (GSHPs) and some variations on both. Operating costs vary depending on location, type of heat pump, and local electricity prices. Moreover, there are significant caveats when comparing efficiency ratings between heat pumps and conventional heating and cooling equipment. All of these factors make the decision over whether to install a heat pump more complicated than it might seem at first.