Definition
HSPF2 (Heating Seasonal Performance Factor 2) is the U.S. Department of Energy rating for how much heat a heat pump delivers per watt-hour of electricity over a typical heating season, measured under the M1 test procedure adopted in 2023. Since January 1, 2023, new split-system heat pumps nationwide must be rated at least 7.5 HSPF2.
Also called: Heating Seasonal Performance Factor 2, HSPF
Why it matters to you.
Central Kentucky heat pumps work through a real heating season with regular winter cold snaps, so HSPF2 describes a large share of a heat pump's yearly electricity, especially in all-electric homes outside gas service. By rating arithmetic, a 9.0 HSPF2 heat pump uses about 17% less electricity than a 7.5 HSPF2 one for the same heating (1 − 7.5/9.0).
Practical guidance.
Compare HSPF2 and SEER2 together from the AHRI Directory listing for the exact matched system on your quote. Also ask how much heating capacity the heat pump keeps at cold temperatures and when backup heat, or a gas or propane furnace on a dual-fuel system, takes over.
How HSPF2 options compare.
| HSPF2 rating | Where it sits | Heating electricity vs. 7.5 HSPF2 for the same heat (1 − 7.5/x) |
|---|---|---|
| 7.5 | Federal minimum, split-system heat pumps | Baseline (0%) |
| 8.0 | Above the minimum | About 6% less |
| 8.5 | Mid-efficiency tier | About 12% less |
| 9.0 | Higher-efficiency tier | About 17% less |
| 10+ | High-efficiency tier, typically variable-speed | About 25% less at 10; more above 10 |
What is the minimum HSPF2 for a new heat pump in Kentucky?
The federal minimum for a new split-system heat pump is 7.5 HSPF2, and it applies nationwide, including Kentucky, for equipment made on or after January 1, 2023. The same heat pump must also meet the 14.3 SEER2 cooling minimum. Packaged heat pumps have a separate 6.7 HSPF2 minimum.
How much does a higher HSPF2 cut heating electricity?
The rating arithmetic is 1 − (7.5 ÷ new HSPF2) for the same heating load. That gives about 6% less at 8.0, about 12% less at 8.5, about 17% less at 9.0 and 25% less at 10. These are ratios of ratings, not bill estimates; ductwork, thermostat habits and backup-heat use change real results.
Should Central Kentucky homeowners prioritize HSPF2 or SEER2?
Both. Central Kentucky's mixed-humid climate has a long, muggy cooling season and a real heating season, and a heat pump does both jobs. Homes that heat only with the heat pump should give HSPF2 at least equal weight; on a dual-fuel system, where a gas or propane furnace covers the coldest days, SEER2 and low-temperature capacity matter relatively more.
Does HSPF2 tell me how a heat pump handles a cold snap?
Not fully. HSPF2 is a seasonal average, while cold-snap comfort depends on how much capacity the unit keeps at low temperatures and when backup heat takes over. ENERGY STAR's cold-climate heat pump designation requires verified low-temperature performance at 5°F, so ask for low-temperature capacity data alongside the HSPF2 rating.
Is HSPF2 the same as the old HSPF rating?
No. HSPF2 uses the newer M1 test procedure, so the same heat pump scores lower in HSPF2 than in the older HSPF. That is why today's 7.5 HSPF2 minimum looks lower than older HSPF figures without being a weaker standard. Compare HSPF2 only with HSPF2.
About this definition
Written by the Feistritzer Heating & Air Conditioning team — family owned and operated in Danville since 1976, Kentucky HVAC license M02584. Definitions inform; a whole-system diagnosis in your home decides.