DOE EERE Research Reports

Compared to oil, at 1984 prices, a payback of 4 to 6 years is possible. One unit operated at a COP in heating of nearly 3.0, including an allowance for pumping energy. The COP of the second unit was lower, still better than oil heating but not cost-effective at today's rates. Some initial reliability problems were also encountered with one unit. This emphasizes the need for astute buying and use of comparative ratings on models at conditions consistent with the application. As water-source heat pump performance is affected by water supply temperatures, the rating must be for temperatures similar to groundwater temperatures in the region where the heat pump will be installed, typically 50 to 55 F in Pennsylvania. A substantial quantity of water is required and proper disposal is a consideration. Ponds were used to receive processed water in both test applications. The source groundwater was obtained from wells of more than 50 feet in depth, which are common at rural residences.

The units tested required no signicant supplemental heat. Although oversizing may effect performance slightly, undersizing the unit would increase supplemental heat usage. The resulting aggregated demand on a winter-peaking utility could be deleterious. A properly-sized groundwater heat pump should have a load profile similar to resistance heat.