HSPF2 (Heating Seasonal Performance Factor 2)

The longer answer

HSPF2 replaced HSPF in 2023 under revised federal test conditions that are more representative of real-world use — numbers read lower than old HSPF for the same hardware. An 8.1 HSPF2 unit is roughly equivalent to mid-9s in old HSPF terms. Always compare like to like.

In Seattle's long heating season, every HSPF2 point compounds: moving from 8.1 to 9.5 trims heating electricity by roughly the ratio of the ratings (~15%), applied to your actual runtime. The SCL instant discount also steps up at each tier — so the rating affects both operating cost and upfront price.