In recent decades, experts have debated the economic feasibility of heat pump systems for room heating in residential houses. One important piece of information for evaluating the feasibility of heat pump systems is the seasonal coefficient of performance, SCOP (or heating season performance factor, HSPF). In the literature, the SCOP (or HSPF) is still given in a single average value for all climate zones and building insulation levels. The use of average values for the SCOP can lead to significant errors in the economic evaluation of heat pump systems because of the dependency of the SCOP (HSPF) on the building specific heating season and its characteristic heating load values. Often it is not clear which type of heat pump is most economically feasible at a given climate and at a building with a given insulation level. Therefore, an economic evaluation of heat pump systems will benefit from the inclusion of climate data and information about the building envelope.

The first goal of this study is to illustrate the economic feasibility of a ground source water-to-air heat pump system and an external air-to-air heat pump system for residential buildings in the ASHRAE climate zones in the United States. The second goal is to discover how the insulation level of the building envelope will influence the economic feasibility of heat pump systems in different climate regions.

The SCOP (HSPF) of the heat pump system is calculated in a dynamic calculation process for the use in a representative residential building with three different qualities of the building envelope to derive the influence of the peak heating load to the SCOP (HSPF) of the heat pump system. A benchmark analysis is done where an air-to-air heat pump and a geothermal heat pump is compared to a conventional furnace system.

Results show that the quality of the building envelope and the location of the building have a significant influence on the SCOP (HSPF) of a heating system. These results validate the economic feasibility of the heat pump technology in all climate zones of the US.