What does a heat pump’s HSPF efficiency rating mean, and how can it be compared to the AFUE ratings of gas heating systems?
Estimating the difference in energy costs between an electric and a gas heating system involves two steps. First, the watts of heat energy obtained for each watt of energy consumed must be determined. Second, the cost of each watt of electricity to each watt of natural gas must be compared. The American Refrigeration Institute tests heat pumps and provides them with efficiency ratings which are recognized by Natural Resources Canada’s Office of Energy Efficiency. The heating efficiency rating is called the heating seasonal performance factor (HSPF) which is defined as the “total heat output in Btu of a heat pump over the entire heating season divided by the total energy in watt hours it uses during that time.” Different HSPF’s are assigned to different regions, as a heat pump’s heating efficiency decreases as the outdoor temperature falls. The HSPF also factors in the use of supplemental heat. The HSPF of the heat pumps we install ranges between 7.7 and 9.5. Since 3.413 Btu’s are equiv