HSPF2 (Heating Seasonal Performance Factor 2) is the U.S. Department of Energy rating for a heat pump's heating efficiency: total seasonal heat delivered in BTUs divided by the watt-hours of electricity used, including defrost and backup heat. It replaced HSPF on January 1, 2023, under a tougher test, so it reads lower for identical equipment.
Why it matters to you
In heating-dominated climates a heat pump runs far more hours heating than cooling, so HSPF2 usually says more about its electricity use there than SEER2 does. Moving from 7.5 to 8.5 HSPF2 uses about 12% less electricity for the same seasonal heat (1 − 7.5/8.5).
Practical guidance
Compare quotes HSPF2 to HSPF2 and confirm the rating in the AHRI Directory for the exact outdoor and indoor combination being installed. In cold climates, also ask for the unit's heating capacity at 5°F, not just its nominal size.
HSPF2 tiers for split heat pumps
| Tier | HSPF2 | Electricity vs. resistance heat | Electricity vs. 7.5 HSPF2 (arithmetic, not a bill estimate) |
|---|---|---|---|
| Electric resistance (baseboard or heat strips) | About 3.4 | Baseline | — |
| Federal minimum (split system) | 7.5 | About 55% less | Baseline |
| ENERGY STAR (split system) | 7.8 | About 56% less | About 4% less |
| ENERGY STAR cold climate | 8.5 | About 60% less | About 12% less |
| Premium (variable-speed) | 10 | About 66% less | About 25% less |
How much less electricity does a higher HSPF2 heat pump use?
For the same seasonal heat, electricity use scales inversely with the rating. Moving from 7.5 to 8.5 HSPF2 uses about 12% less electricity (1 − 7.5/8.5), and moving to 10 HSPF2 uses about 25% less (1 − 7.5/10). These are ratios under standard test conditions, not an estimate for any specific home.
How does a heat pump compare with electric resistance heat?
Electric resistance heat, such as baseboards, furnace heat strips or an electric furnace, turns one watt-hour into 3.412 BTUs, the equivalent of an HSPF of about 3.4. A heat pump rated 7.5 HSPF2 needs about 55% less electricity for the same seasonal heat (1 − 3.412/7.5), before real-world factors like ductwork and installation quality.
What is the minimum HSPF2 for a new heat pump?
Federal minimums that took effect on January 1, 2023 apply nationwide: 7.5 HSPF2 for split-system heat pumps and 6.7 HSPF2 for packaged units. ENERGY STAR sets a higher bar, and its cold-climate category adds requirements for performance at 5°F.
Does HSPF2 tell me how a heat pump performs in a cold climate?
Only partly. HSPF2 is calculated for a single moderate climate profile, so two units with similar ratings can behave very differently on a 5°F morning. For cold regions, compare rated heating capacity and efficiency at low outdoor temperatures, which ENERGY STAR cold-climate listings publish.