Climate zones and heat-pump COP: the presets we use
A heat pump's seasonal COP falls as winters get colder, because it has to extract heat from colder air. This site groups the US into four planning zones - mild (COP 3.2), mixed (2.8), cold (2.4) and very cold (2.0) - and pairs each with a per-square-foot annual heat-demand band. These are documented assumptions, not measurements of your home.
Why COP drops with cold
The colder the outdoor air, the less heat is available to move and the harder the compressor works, so COP falls. Cold-climate (ccASHP) units hold useful output into the teens (F) but still derate on the coldest days, which is why a backup heat source is common in severe climates.
The heat-demand presets
We estimate annual useful heat as square footage times a per-square-foot band that rises with climate severity. These bands are illustrative planning figures so a visitor without an energy audit can get an estimate - your real demand depends on insulation, air sealing, windows and thermostat habits.
| Climate zone | Seasonal COP | HSPF2 equiv. | Heat-demand band |
|---|---|---|---|
| Hot / mild (e.g. Gulf South, Southwest) | 3.2 | about 10.9 | 8,000 BTU per sq ft per year |
| Mixed (e.g. Mid-Atlantic, Pacific NW, lower Midwest) | 2.8 | about 9.6 | 18,000 BTU per sq ft per year |
| Cold (e.g. Northeast, upper Midwest) | 2.4 | about 8.2 | 28,000 BTU per sq ft per year |
| Very cold (e.g. northern New England, Mountain West, Upper Plains) | 2 | about 6.8 | 38,000 BTU per sq ft per year |
Frequently asked questions
Which zone is my state?
Each state page uses a default zone based on its climate, but you can override it in the calculator. Northern New England, the Upper Plains and the Mountain West are very cold; the Gulf South and Southwest are mild.
Are these COP values guaranteed?
No - they are planning assumptions for a modern cold-climate heat pump. Your real seasonal COP depends on the equipment, sizing, controls and the actual winter. Always confirm with an HVAC professional.
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Last updated: 2026-06-29