What a cold climate heat pump has to prove at 5 degrees
ENERGY STAR sets the cold climate designation at 70 percent of rated capacity at 5F with a COP of at least 1.75; its other qualifying heat pumps have a 45 percent backstop.
What this means
The designation is a measured threshold, not a description. ENERGY STAR Version 6.2 requires a coefficient of performance of at least 1.75 at 5 degrees Fahrenheit together with heating capacity at 5 degrees of at least 70 percent of the capacity at 47 degrees. Other ENERGY STAR-qualified heat pumps meet the same 1.75 COP backstop with a 45 percent low-temperature capacity requirement; that is not a rule for every heat pump on the market.
Equipment and model context
Cross-brand explanation; product figures come from the model documentation
- Residential central air-source heat pumps rated under ENERGY STAR Version 6.2
These figures are the ENERGY STAR Version 6.2 criteria for central air conditioners and heat pumps in the United States. Manufacturers also publish their own low-temperature claims for individual models, and those are separate statements that a cold climate designation does not automatically confirm.
What this guide covers
- A quotation describes equipment as suitable for cold climates without citing any figure.
- A rebate or incentive is written specifically for cold climate heat pumps.
- Two heat pumps carry similar HSPF2 ratings and behaviour that diverges in January.
What changes the answer
- ENERGY STAR Version 6.2 defines the cold climate designation by a COP of at least 1.75 at 5 degrees Fahrenheit and heating capacity at 5 degrees of at least 70 percent of capacity at 47 degrees.
- Other heat pumps qualifying under the ENERGY STAR specification are held to the same 1.75 COP backstop at 5 degrees but only 45 percent of the 47 degree capacity.
- ENERGY STAR defines COP as the ratio of average space heating delivered to average electrical energy consumed.
| Requirement at 5 degrees Fahrenheit | Cold climate designation | Other ENERGY STAR heat pumps |
|---|---|---|
| Minimum coefficient of performance | 1.75 | 1.75 |
| Heating capacity as a share of 47 degree capacity | At least 70 percent | At least 45 percent |
| What the test measures | Delivered heating against electrical input | The same measurement |
| What the difference shows | More of the 47 degree output still available at 5 degrees | A lower qualifying capacity backstop at the same temperature |
The capacity number is the one that matters
Both ENERGY STAR categories have to reach the same efficiency floor at 5 degrees Fahrenheit. A coefficient of performance of 1.75 means the equipment still delivers 1.75 units of heat for every unit of electricity it consumes, and ENERGY STAR applies that backstop to qualifying heat pumps rather than only to the cold climate subset.
What separates the two ENERGY STAR categories is how much rated heat is left. A cold climate unit has to still produce at least 70 percent of its 47 degree capacity when the outdoor air is at 5 degrees. Another qualifying unit can fall to 45 percent and still meet the low-temperature backstop.
That gap informs backup-heat design, but it does not predict the share of a building load either unit will carry. The building's heat loss rises as outdoor temperature falls, so capacity at 5 degrees has to be compared with a load calculation at the same condition.
Why HSPF2 does not answer this question
HSPF2 is a seasonal figure. It averages performance across a heating season dominated by hours nowhere near 5 degrees, so two units with similar seasonal ratings can behave unlike each other on the coldest nights.
The low-temperature criteria exist precisely because the seasonal number smooths that away. A capacity requirement measured at one temperature answers a question the seasonal average is not designed to answer.
So a specification that quotes only HSPF2 has said nothing about cold weather capability, and a specification that quotes only a minimum operating temperature has said only where the machine will still run, not how much it will still deliver.
What the designation does not tell you
It does not describe behaviour below 5 degrees. The criteria are anchored at a single test point, and lower-temperature performance is a separate manufacturer claim. For example, METUS publishes full capacity to minus 5 and guaranteed heating to minus 11 for the cited intelli-HEAT H2i configuration; those statements have their own product scope.
It does not size the backup heat. Even at 70 percent of rated capacity, a design that relies on the heat pump alone at 5 degrees has to have started from a capacity that was large enough, and that is a load calculation rather than a rating.
It also does not settle the running cost. A COP of 1.75 at 5 degrees is a technical statement about efficiency, and whether that is cheaper than the alternative depends on the price of electricity against the price of whatever else could heat the building.
How to use the figures when comparing quotations
Ask for the capacity at 5 degrees in the same units as the nominal capacity rather than as a percentage. A percentage of an unstated number is not comparable between two proposals for the same house.
Then ask what carries the remainder at design condition, and at what temperature the control hands over to it. On a dual fuel system that is a changeover setting; on an all-electric system it is a bank of resistance heat whose running cost is nothing like the same.
Those two answers, taken together, describe the winter. The designation on the badge is a filter that narrows the field, not a substitute for either of them.
| Question to ask | Why it matters |
|---|---|
| Does it hold the ENERGY STAR cold climate designation | That is a defined 70 percent capacity threshold at 5 degrees |
| What is the capacity at 5 degrees in BTU per hour | A percentage of an unstated nominal is not comparable |
| What is the design heating load of the house | Capacity only means something against a load |
| What supplies the shortfall at design condition | Backup fuel and running cost differ enormously |
| At what temperature does the control hand over | An early handover wastes the capability being paid for |
| What does the manufacturer claim below 5 degrees | The designation is anchored at one test point only |
Both categories meet the same efficiency floor at the same test point. The capacity requirement is what separates them, and it decides how much backup heat the winter needs.
- Capacity at 47 degreesThe reference point both requirements are measured against
- COP of 1.75 at 5 degreesApplies to both categories alike
- 70 percent capacity at 5 degreesThe cold climate designation threshold
- 45 percent capacity at 5 degreesThe requirement without the designation
Questions people ask about this
What makes a heat pump a cold climate heat pump?
Under ENERGY STAR Version 6.2 it has to reach a coefficient of performance of at least 1.75 at 5 degrees Fahrenheit and still deliver at least 70 percent of its 47 degree heating capacity at that temperature.
How is a cold climate heat pump different from a normal one?
Within ENERGY STAR Version 6.2, the 5 degree efficiency backstop is the same 1.75 COP. The difference is capacity: a cold-climate-designated unit must hold at least 70 percent of its 47 degree output, while another qualifying heat pump has a 45 percent backstop.
Does a high HSPF2 mean good cold weather performance?
Not on its own. HSPF2 averages a whole heating season, most of which is far warmer than 5 degrees, so two units with similar seasonal ratings can differ by a wide margin in what they deliver on the coldest nights.
What does COP of 1.75 actually mean?
ENERGY STAR defines COP as the ratio of the average rate of space heating delivered to the average rate of electrical energy consumed, so 1.75 means 1.75 units of heat for every unit of electricity at that test condition.
Does the designation say anything about temperatures below 5 degrees?
No. The criteria are anchored at 5 degrees Fahrenheit. Any claim about performance at lower temperatures is a separate manufacturer statement that has to be checked on its own evidence.
Do I still need backup heat with a cold climate heat pump?
That depends on the capacity at design condition against the building's heat loss, not on the designation. Holding 70 percent of rated capacity still leaves a shortfall if the rated capacity was not large enough to begin with.
Evidence recordHow this page was checked
government guidance, official manufacturer support article · checked 2026-09-08
Every technical claim above was written from primary documentation held in the HVAC Bench evidence record: United States Environmental Protection Agency ENERGY STAR and Mitsubishi Electric Trane HVAC US technical literature. Where a source limits a definition to certain models, test conditions, or product classes, that limit is repeated here rather than generalised.
- Documentation class
- government guidance, official manufacturer support article
- Scope of the definition
- Confirm against the exact model manual
- Last checked
- 2026-09-08