These systems work on a different principle than an ordinary furnace/air conditioning system and require little maintenance or attention from homeowners. Furnaces create heat by burning a fuel—typically natural gas, propane or fuel oil. With geoexchange systems there’s no need to create heat or for chemical combustion. Instead the earth’s natural heat is collected in winter through a series of pipes—called a loop—installed below the surface of the ground or submersed in a pond or lake.

Fluid circulating in the loop carries this heat to the home. An indoor system then uses electrically-driven compressors and heat exchangers in a vapor compression cycle—the same principle employed in a refrigerator—to concentrate the earth’s energy and release it into the home at a higher temperature. In typical systems duct fans distribute the heat to various rooms.

In summer the process is reversed in order to cool the home. Excess heat is drawn from the home, expelled to the loop and absorbed by the earth. GeoExchange systems provide cooling in the same way that a refrigerator keeps its contents cool—by drawing heat from the interior, not by injecting cold air.