How does geothermal heating and cooling work?

Geothermal systems use the stable temperature of the earth (about 55°F year-round in Illinois, regardless of surface temperature) as a heat source in winter and a heat sink in summer.

A closed loop of pipes buried in the ground circulates fluid that absorbs or releases heat, and a heat pump inside the home moves that heat in or out.

Because the system moves existing heat rather than generating it by burning fuel, it can deliver 3–5 units of heating energy for every 1 unit of electricity used. It's the most efficient heating and cooling technology available.