The EPA reports that geothermal conditioning systems provide the best life cycle cost payback of all the conditioning systems available. Heat transfer is provided by exchanging heat from a source fluid (water, glycol, etc) to the Earth through pipes routed underground or in a pond. A ground-source heat pump (GSHP) is usually utilized to transfer this heat exchange to conditioned spaces. They use the same refrigeration technology as standard air heat-pumps, instead of using fans to exchange heat to outdoor air they use pumps and fluid to transfer to or from the ground. GSHP’s have been shown to reduce energy and corresponding emissions by over 40%. GSHP’s can condition air directly to the space or condition water that can then be used in fan coils or directly in a radiant floor or ceiling.

The ground temperature stays very close to the same temperature year round below 10-foot depths. In San Francisco this is around 60°F, in southern California it’s closer to 65°F. Heat transfer through fluids is much more efficient than exchanging heat through air. If only moderate cooling is required, the heat pump may be bypassed and only a circulation pump is needed to utilize the natural cooling of the Earth to condition the circulation fluid.