HSPF2 (Heating Seasonal Performance Factor 2)
The federal rating for how much heat a heat pump delivers per unit of electricity across a winter — the heating-season counterpart to SEER2's cooling rating.
HSPF2 measures a heat pump's heating output relative to the electricity it consumes over a full heating season, using the same tougher M1 test procedure that replaced SEER with SEER2 in 2023. The federal floor is 7.5, which works out to roughly 2.2 units of heat delivered per unit of electricity used — meaning even a code-minimum heat pump heats more than twice as efficiently as basic electric-resistance heat.
HSPF2 rises through the same standard/high/premium tiers as SEER2, since the same equipment upgrade — a better compressor and coil — improves both ratings together. It only applies to heat pumps; a gas furnace's efficiency is rated by AFUE instead.