Savings in energy consumption by residential heat pumps: the effects of lower indoor temperatures and of night setback

Abstract

The energy saving potential of reduced indoor temperatures and of night setback is examined for residential heat pumps. Close scrutiny of the relationship of energy consumption to heating load is required, particularly if night setback is anticipated. The morning recovery period occurs during what is typically the coldest part of the dat, calling for maximum output from the system when its coefficient of performance (COP) is lowest. This effect and the desire for rapid temperature recovery indicate increased use of auxiliary resistance heaters and might result in an increase, rather than a saving, in total energy consumption. It is found, however, that energy savings ranging from 40% in Atlanta to 20% in Minneapolis may be realized if indoor temperatures are reduced from 72/sup 0/ to 68/sup 0/F in the daytime and 60/sup 0/F at night. The National Bureau of Standards Load Determination (NBSLD) computer program was used to calculate heating loads. It was modified to evaluate the heating capacity, energy consumption, and running time of heat pumps on an hourly basis as a function of outdoor dry bulb temperature, and to simulate the use and energy consumption of auxiliary resistance heaters. Annual heating loads, energy consumption, percentage savings, and seasonalmore » COP's are presented for several indoor temperature regimes and a variety of climatic conditions. Hourly profiles of these quantities give some insight into the energy savings found.« less