Economic Efficiency in the Sizing of Residential Heat Pumps

摘要

This report provides a methodology for determining the optimal heat pump size, in terms of heating output capacity, for residential installations having annual heating requirements significantly greater than annual cooling requirements. The optimal size heat pump is defined as the size for which total present value, life-cycle heating and cooling costs (including equipment costs) are minimized. Incremental energy savings from increasing the output capacity of the heat pump are calculated using hourly simulation models of heat pump and building performance developed at NBS. The dollar value of the incremental savings, in present-value, life-cycle terms, is then calculated and compared with incremental costs to determine the optimal heat pump size. A base case analysis of an 1800 square-foot house in the Chicago climate shows that a slightly larger heat pump size than would typically be selected for air conditioning purposes alone is optimal for the assumptions specified. A number of sensitivity analyses are performed to show the effects of changes in load size, degradation coefficients, power utilization efficiency, economic assumptions and geographic location on the optimal heat pump size.