By using the ground as the source for heat, much like an airsource heat pump uses air to remove the heat from the air on a cold day a geothermal system using the more consistent earth as the source for pulling heat out of the ground to heat your home in the winter and cool your home in the summer. The earths more consistent temperatures allow the system to work better than an air source system and in general the Geothermal system is more effiencent than any other type of heating used in homes.