During the summer months fluid dissipates heat from the house to the ground, then before returning to the home, the fluid is cooled by relatively constant ground temperatures (50-55 degrees in Iowa). The cold from the fluid is converted to cool air by circulating it through water-to-refrigerant and refrigerant-to-air heat exchangers (similar to a car radiator).

Reliability and efficiency are good reasons to buy a heat pump, but it is also the choice for environmental reasons. The U.S. Environmental Protection Agency (EPA) ranks ground source heat pumps as having the lowest overall environmental cost, and highest "source performance."