Learn · Cold-climate performance
Will a heat pump keep up in real cold?
It's the one question that stops people from buying a heat pump: on the coldest night of the year, will it actually keep my house warm? Most articles answer with a reassuring anecdote — "they run fine in Maine" — and stop there. That's not an answer you can act on. The real answer has two parts: how cold it actually gets where you live, and what the specific unit on your quote is certified to deliver at that temperature. We have the certified numbers for 5,544 cold-climate units, so this page answers it with data instead of vibes.
The short answer
- Yes — a modern cold-climate heat pump keeps up across almost all of the U.S. In our ranked corpus of 5,544 cold-climate units, the median still runs at a COP of 1.98 at 5°F — moving about twice the heat of the electricity it draws — while holding 83% of its rated heating capacity at that temperature.
- The surprise: 1,048 of those units make more heat at 5°F than they do at 47°F. Their variable-speed compressors ramp up as it gets colder, exactly when you need it.
- What actually decides it for you: your climate's design temperature (how cold your coldest hours really get) versus the unit's certified capacity at that temperature. Match those two and it keeps up. That match — not a brand — is the whole game.
First: how cold does it actually get where you live?
HVAC engineers don't size equipment to the record low. They size to the 99% heating design temperature — the temperature your area stays above for 99% of the hours in a year. Your location is colder than this only about 1% of the year, roughly 88 hours. It's the honest "design cold" a system has to cover, and it varies enormously across the country.
| City | Climate zone | Heating design temp |
|---|---|---|
| Miami, FL | 1A | 46.3°F (99.6%) |
| Phoenix, AZ | 2B | 37.2°F (99.6%) |
| Houston, TX | 2A | 27.7°F (99.6%) |
| Seattle, WA | 4C | 23.8°F (99.6%) |
| Dallas, TX | 3A | 19.9°F (99.6%) |
| Atlanta, GA | 3A | 18.8°F (99.6%) |
| New York, NY | 4A | 12.8°F (99.6%) |
| Nashville, TN | 4A | 11.6°F (99.6%) |
| Boston, MA | 5A | 7.7°F (99.6%) |
| Denver, CO | 5B | −4°F (99.6%) |
| Chicago, IL | 5A | −5°F (99.6%) |
| Minneapolis, MN | 6A | −14.9°F (99.6%) |
| Duluth, MN | 7 | −21°F (99%) |
| Fairbanks, AK | 8 | −40°F (99%) |
Design cold spans about 46°F in Miami to −40°F in Fairbanks — a 90-degree range. The reason 5°F is the number everyone tests and talks about: it sits right in the middle of where climate zones 5 through 8 actually live, so it's the fair, standardized point to measure whether a unit still performs where cold matters. (Values marked 99.6% are the colder, more conservative ASHRAE percentile; Duluth and Fairbanks are the 99% percentile from a different federal source — see the note below.)
What happens to a heat pump as it gets colder
A heat pump doesn't create heat — it moves it from the outdoor air into your home. As the outdoor temperature drops, two things work against it: there's less heat energy in colder air to extract, and the gap between the frigid outdoor air and your warm indoor setpoint grows, so the compressor works harder to move less heat. That's why both heating capacity (how many BTUs it can deliver) and efficiency (COP) fall as it gets colder — and it happens at exactly the moment your house needs the most heat. Those two curves crossing is the entire reason sizing to your design temperature matters.
But "falls" doesn't mean "quits." The best variable-speed cold-climate units barely derate at all, and some deliver more capacity in the cold by spinning their compressors up. In our data, 2,157 units hold at least 90% of their 47°F capacity down to 5°F, and 1,048 exceed 100%. That's the difference between a bargain single-stage unit and a true cold-climate machine — and it's invisible unless you look at the certified 5°F numbers.
What the certified data actually shows
This is the part no other site gives you. Every unit below is AHRI-certified, and we publish the measured heating performance at 5°F for each one. Across the 5,544 cold-climate units we rank (4,036 ductless mini-splits, 1,508 ducted systems):
top 10%: 2.20 · best: 2.89
held by the median unit at 5°F
down to 5°F
than at 47°F (variable-speed)
Put the COP number in context: electric-resistance backup heat runs at a COP of exactly 1.0 — one unit of heat per unit of electricity. A median cold-climate heat pump at 5°F is still around 2.0, roughly twice as efficient as the "emergency heat" it's often assumed to fall back on. It isn't limping along in the cold; it's still winning.
What "cold-climate rated" actually means
Two different bars use the phrase, and they're not the same:
- ENERGY STAR cold-climate (the market label): COP of at least 1.75 at 5°F and heating capacity at 5°F of at least 70% of the 47°F rating (plus seasonal HSPF2/SEER2 floors). This is the badge you'll see on product listings.
- DOE Cold Climate Challenge (best-in-class): a tougher target of COP 2.1–2.4 at 5°F and 100% capacity retention — no derate at all. Units that clear this are the ones you want at the coldest design temperatures.
Our "cold-climate" ranking uses certified 5°F performance, so you can see not just whether a unit wears the badge, but how far past the minimum it actually goes.
So — will it keep up? Zone by zone
- Zones 1–4 (Miami to Nashville/NYC/Seattle, design temps above ~10°F): almost any modern heat pump — cold-climate rated or not — carries the whole winter comfortably. This isn't a close call.
- Zone 5 (Chicago, Boston, Denver, design temps around −5°F): a cold-climate unit sized to your load keeps up on its own. Choose one with strong 5°F capacity retention and you won't touch backup heat most winters.
- Zone 6 (Minneapolis, Burlington, design temps around −15°F): a good cold-climate unit still carries it, but sizing to the design temperature (a real Manual J load calculation) matters, and modest backup covers the worst nights.
- Zones 7–8 (Duluth, interior Alaska, −21°F to −40°F): a heat pump carries most of the season and saves real money doing it, but at these design temps you plan for backup or a dual-fuel setup for the extreme hours. A heat pump alone at −40°F is the one place the honest answer is "not by itself."
Notice what decides every one of these: the design temperature versus the unit's certified capacity. That's a number you can look up — not a leap of faith.
See the 5,544 cold-climate units ranked by COP at 5°F → Compare heating cost vs. gas & resistance → Look up a specific model's 5°F numbers →
Common questions
Do heat pumps really work below freezing?
Yes. A heat pump moves heat rather than burning fuel, and there is usable heat in outdoor air well below 0°F. Across the 5,544 cold-climate units in our database, the median unit still delivers a COP of 1.98 at 5°F — it moves about 2.0× as much heat energy as the electricity it draws, at a temperature far below freezing. The question isn't whether it runs; it's whether the specific unit still delivers enough heat for your home on your coldest night.
At what temperature does a heat pump stop working?
There's no single cutoff — it's a slope, not a cliff. As it gets colder, a heat pump delivers less heat and does it less efficiently, because there's less heat in the outside air to move and a bigger temperature gap to bridge. Many cold-climate models are rated to operate to −13°F or −22°F; some go lower. What matters is the certified numbers at your design temperature, not a marketing "operates down to" figure — which is why we publish the measured 5°F capacity and COP per unit.
What is a good COP at 5°F?
The ENERGY STAR cold-climate bar is a COP of at least 1.75 at 5°F; the tougher DOE Cold Climate Challenge target is 2.1–2.4. In our ranked cold-climate corpus the median unit is COP 1.98 at 5°F, the top 10% clear 2.20, and the best reach 2.89. Anything at or above ~2.0 is moving at least twice the heat of the electricity it uses — still far better than electric-resistance backup, which is exactly 1.0.
Will a heat pump keep up in a very cold climate like Minnesota or Maine?
In climate zones 5 and 6 (roughly Chicago/Boston to Minneapolis, design temps around −5°F to −15°F), a correctly sized cold-climate heat pump keeps up — 2,157 of the 5,544 units we rank hold at least 90% of their rated heating capacity down to 5°F, and 1,048 actually produce more heat at 5°F than at 47°F because their variable-speed compressors ramp up. In zones 7–8 (Duluth, interior Alaska, design temps of −21°F to −40°F), a heat pump can still carry most of the season, but you size for the design load and plan backup heat for the extremes. The move is to match the unit's certified 5°F capacity to your home's heat load — not to assume it won't work.
Do I still need backup heat with a cold-climate heat pump?
It depends on your design temperature and how the unit is sized. In milder zones (1–4) a properly sized heat pump carries the whole winter on its own. In the coldest zones (7–8), or when a unit is sized to the average day rather than the design day, a backup — electric-resistance strips, or a furnace in a dual-fuel setup — covers the handful of hours per year below the unit's effective range. The colder your design temperature, the more the sizing and backup plan matter, which is the part every "heat pumps work in the cold" article skips.
Corpus figures (COP and heating-capacity retention at 5°F) are computed at build time from our normalized dataset — data current as of July 12, 2026 — over the same 5,544 rebadge-collapsed, AHRI-certified cold-climate units our verdict hub ranks. We publish our derived layer and cite the AHRI reference number; we do not republish AHRI's table verbatim. Climate zones per the DOE/PNNL IECC climate-zone map. Heating design temperatures (99.6% percentile) extracted from the FGIA ASHRAE design-temperature reference (2005 ASHRAE Handbook of Fundamentals basis); Duluth and Fairbanks (99% percentile) from the ENERGY STAR County-Level Design Temperature Reference Guide. Cold-climate criteria per ENERGY STAR and the DOE Residential Cold Climate Heat Pump Challenge. Heat-pump cold-weather physics per the DOE Building America cold-climate sizing guide.
Written by Erin Rose. Efficiency and capacity figures trace to AHRI/ENERGY STAR certified data; computed fields (capacity retention, corpus percentiles) are our own derived layer, formulas in our methodology. No fabricated specs, no star ratings.