What do HSPF2 and COP mean on a heat pump, and which numbers matter in a Minnesota winter?
HSPF2 is a heat pump's heating efficiency averaged over a season in one reference climate; COP is its efficiency at a single outdoor temperature. In Minnesota, the numbers that matter most are the COP and heating capacity at 5°F. ENERGY STAR's cold-climate label requires a COP of at least 1.75 at 5°F and 70% of rated capacity.
Key points
- HSPF2 is a seasonal average in Btu per watt-hour, calculated for one reference climate. Divide by 3.412 to read it as an average COP.
- COP is heat out divided by electricity in, at one set of conditions. Electric resistance heat is a COP of 1.
- ENERGY STAR cold-climate heat pumps need COP of at least 1.75 at 5°F, at least 70% of their 47°F capacity at 5°F, and a controls check.
- Capacity at 5°F and below decides when backup heat takes over. Minneapolis and Saint Paul's heating design temperature is -15°F.
- The NEEP cold-climate list shows capacity and COP at 5°F, 17°F and 47°F for each matched system.
HSPF2 is a heat pump's heating efficiency averaged over a whole season, and COP (coefficient of performance) is its efficiency at one specific outdoor temperature. In a Minnesota winter, the numbers that tell you the most are the COP and heating capacity at 5°F, because that's where heat pumps start to struggle and where our winters spend real time.
HSPF2 is still useful as a screen. It just can't tell you what happens on a -15°F night.
What does HSPF2 mean on a heat pump?
ENERGY STAR's specification defines HSPF2 as the total space heating needed over a heating season in a reference climate DOE calls region IV, in Btu, divided by the electricity the heat pump system uses over that season, in watt-hours. The "2" means it's measured under DOE's newer test procedure, in effect since January 1, 2023, so HSPF2 numbers aren't directly comparable with old HSPF numbers.
Two things follow from that definition:
- It's an average. A high HSPF2 can come from excellent mild-weather efficiency, even if the unit falls off hard below zero.
- It's one climate. The reference isn't your climate, and a Minnesota season includes stretches well below zero that a single average smooths over.
A handy conversion: HSPF2 is in Btu per watt-hour, and one watt-hour is 3.412 Btu. Divide HSPF2 by 3.412 and you get a rough seasonal-average COP. The federal minimum for a split heat pump, 7.5 HSPF2, works out to about 2.2. ENERGY STAR's cold-climate bar for ducted systems, 8.1, is about 2.4.
What does COP mean on a heat pump?
COP is heat delivered divided by electricity used, at a single set of operating conditions. It has no units. Electric resistance heat (baseboard, an electric furnace, or a heat pump's backup strips) is a COP of 1: one unit of electricity in, one unit of heat out. A heat pump at COP 3 delivers three units of heat for each unit of electricity.
COP changes with the weather. The colder the outdoor air, the harder the compressor works to pull heat out of it, so COP drops. That's why a single COP number without a temperature attached means very little. Look for COP at 47°F, 17°F and 5°F.
The ENERGY STAR cold-climate criteria
ENERGY STAR's current heat pump specification (version 6.2) sets two tiers. Its standard label for split heat pumps requires at least 15.2 SEER2, 11.0 EER2 and 7.8 HSPF2. The Cold Climate label adds low-temperature performance:
| Cold Climate requirement | Ducted split | Ductless split |
|---|---|---|
| SEER2 | 15.2 or higher | 15.2 or higher |
| HSPF2 | 8.1 or higher | 8.5 or higher |
| COP at 5°F | 1.75 or higher | 1.75 or higher |
| Heating capacity at 5°F | At least 70% of capacity at 47°F | At least 70% of capacity at 47°F |
| Controls verification | Required | Required |
The controls verification procedure confirms the unit hits those 5°F numbers under its own controls, the way it would run in your house, not in a special test mode. Version 6.2 also has manufacturers report the heating capacity and COP at 5°F for heat pumps they certify. ENERGY STAR's product finder on energystar.gov lets you search certified models.
Why does heat pump capacity at 5°F matter?
Efficiency tells you what each hour of heat costs. Capacity tells you whether the heat pump can keep up at all. A heat pump rated 36,000 Btu per hour at 47°F that just meets the 70% rule still delivers at least 25,200 Btu per hour at 5°F. Whether that covers your house depends on your house.
That's where a Manual J load calculation comes in. Minnesota's residential energy code lists a winter design temperature of -15°F for Minneapolis and Saint Paul. A load calculation tells you how many Btu per hour your house loses at that temperature. Lay the heat pump's capacity curve against it, and you find the balance point: the outdoor temperature below which the heat pump alone can't keep up and backup heat has to help.
In most Twin Cities installs, that backup is either the gas furnace (dual fuel) or electric resistance strips. Mitsubishi, for example, rates its Hyper-Heat models to run down to -13°F, but capacity still drops as it gets colder, so planning the backup is part of the design, not an afterthought. Our cold-climate heat pump guide and dual-fuel guide cover the setups.
How to read a spec sheet or the NEEP list
The Northeast Energy Efficiency Partnerships (NEEP) keeps a cold-climate air-source heat pump list aimed at climate zone 4 and colder. Manufacturers report capacity and efficiency for each matched outdoor and indoor combination at 47°F, 17°F and 5°F, often with minimum, rated and maximum columns. The rated column at 47°F should match the AHRI certificate.
When you read one:
- Find the exact match. The outdoor unit, the indoor unit or coil, and for ducted systems the furnace or air handler.
- Read maximum capacity at 5°F. That's the most heat it can make on a cold day. Compare it with your load calculation.
- Read COP at 5°F at maximum capacity. NEEP's specification, like ENERGY STAR's, uses a 1.75 floor.
- Check the minimum capacity at 47°F. A low minimum means the unit can turn down in fall and spring instead of short-cycling.
- Look for the lowest operating temperature in the manufacturer's literature, and ask how the unit behaves below it.
Then ask each contractor for the same five numbers. If a quote only lists HSPF2, ask for the rest.
What affects heat pump running costs in Minnesota?
- Your fuel. Replacing propane or electric-resistance heat usually shows the biggest savings. With natural gas, the math depends on your rates, and many homes set a switchover temperature. Our heat pump vs furnace comparison runs through it.
- Defrost. Heat pumps periodically defrost the outdoor coil in winter, which costs a little efficiency. Our post on the heat pump defrost cycle explains what's normal.
- Snow and placement. Mount the outdoor unit above the snow line with room for meltwater to drain.
Cost, rebates and next steps
Heat pump installs with us run $7,500–$14,500, and ductless mini-splits run $4,200–$12,500. Xcel Energy lists rebates for cold-climate air-source heat pumps and mini-splits in Minnesota, some requiring a contractor in its Trade Partner Network, and CenterPoint Energy's ducted heat pump rebate applies only when the heat pump is paired with a gas furnace. Ask whether the rebate needs a registered contractor before you count on it. The federal 25C tax credit ended for equipment placed in service after December 31, 2025.
For a written quote that lists capacity and COP at 5°F for each option, start from our heat pump page, our ductless mini-split page, or the Minneapolis heat pump page. Call 612-429-3465; we're open 7 days, 7am–9pm.
Questions
What is a good HSPF2 for Minnesota?
The federal minimum for a split heat pump is 7.5 HSPF2. ENERGY STAR's cold-climate bar is 8.1 for ducted split systems and 8.5 for ductless. Those are useful screens, but HSPF2 is calculated for one reference climate, not a Minnesota winter, so after the screen, compare the capacity and COP at 5°F and the lowest temperature the manufacturer says the unit will run.
What does a COP of 2 mean?
It means the heat pump delivers two units of heat for every unit of electricity it uses at that temperature. Electric baseboard or an electric furnace delivers one unit of heat per unit of electricity, a COP of 1. So a heat pump running at COP 2 uses about half the electricity of resistance heat for the same warmth. COP drops as it gets colder outside.
Why does the 5°F rating matter so much?
Because that's where most heat pumps start to struggle and where a Minnesota winter spends real time. At 5°F you want to know two things: how many Btu per hour the unit still delivers, and how efficiently. The first decides how often backup heat runs; the second decides what each of those hours costs. ENERGY STAR and NEEP both report this test point.
Is a heat pump with a high COP cheaper to run than my gas furnace?
It depends on your electric and gas rates and the outdoor temperature. As COP falls in deep cold, electric heat can cost more per hour than natural gas, which is why many Minnesota homes pair a heat pump with a gas furnace as dual fuel and set a switchover temperature. Propane and electric-resistance homes usually gain the most.
Sources
- cold-climate air-source heat pump list ashp.neep.org
- ENERGY STAR energystar.gov
- U.S. Department of Energy energy.gov
- AHRI Directory of Certified Product Performance ahridirectory.org