What is HSPF (and HSPF2)? Heat pump heating efficiency
HSPF (Heating Seasonal Performance Factor) is a heat pump's seasonal heating efficiency: total heat delivered (BTU) per watt-hour of electricity used over a heating season. HSPF2 is the stricter 2023 test version (roughly 0.85x the old HSPF). To convert to a COP, divide HSPF by 3.412 - so HSPF2 about 8.5 is about COP 2.5.
HSPF vs HSPF2
The US switched to HSPF2 testing in 2023; HSPF2 numbers are about 15% lower than the old HSPF for the same unit because the test conditions are tougher. A modern ducted heat pump is roughly HSPF2 7.5-10; ductless mini-splits can be higher.
HSPF to COP
Seasonal COP equals HSPF divided by 3.412. So HSPF2 8.2 is about COP 2.4, HSPF2 9.6 is about COP 2.8, HSPF2 10.9 is about COP 3.2. This site uses seasonal COP directly in the cost math; the climate-zone presets map to these HSPF2 values.
Why it drives cost
A higher HSPF/COP means each kWh moves more heat, so heating costs less at the same electricity price. It is the single biggest lever on a heat pump's running cost besides your electricity rate.
Frequently asked questions
What is a good HSPF2?
For a cold climate, look for HSPF2 8.5 or higher and a cold-climate (ccASHP) rating that holds capacity at low temperatures. In mild climates, almost any modern heat pump performs well.
How do I convert HSPF2 to COP?
Divide by 3.412. An HSPF2 of 8.5 is about COP 2.5, meaning 2.5 units of heat per unit of electricity, averaged over the season.
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Last updated: 2026-06-29