HSPF stands for "Heating Seasonal Performance Factor". It is a measure of the energy efficiency of heat pumps used for heating (as opposed to SEER: energy efficiency coefficient in air conditioning mode).
HSPF measures the amount of heat in BTUs (British Thermal Units) produced by a heat pump during a heating season, divided by the amount of electrical energy in watt-hours consumed during the same period.
In other words, the higher the HSPF, the more efficient the heat pump is at heating a home. HSPF is often used to compare the energy performance of different heat pumps and to help consumers choose the most efficient system for their heating needs.
