The electric resistance elements installed with residential electric air-source heat pumps and the lack of efficient control poses a problem for the air-source heat pump's value as an energy saver in Northern U.S. climates. This paper presents monitoring results of a heat pump with staged capacity capable of providing the seasonal heating needs of houses located in heating dominated climates without use of electric resistance elements.

A multi-capacity air source heat pump, installed as the central forced-air heating system at five residences in the Pacific Northwest, was monitored during the heating season. Results include energy use and "real world" efficiency by season and by outdoor temperature. The results of this study show the multi-capacity air-source heat pump is capable of meeting the heating needs of homes without the use of resistance elements even in cold climates. The value of a heat pump installed without electric resistance heat is presented for various Northwest climates. Occupant comfort issues are also discussed.