A cold-climate (hyper-heat) air-source heat pump is engineered to keep delivering heat well below freezing — past Keene's average winter lows near 12°F. It is the honest answer to "will a heat pump actually work in a New Hampshire winter." Sized at the cold design temperature, with a backup planned for the deepest snaps, it carries most of the season on electricity instead of fuel.
How a cold-climate heat pump holds capacity
A heat pump moves heat rather than burning fuel, so even in winter it pulls usable heat from cold outdoor air. Cold-climate models use enhanced compressors and refrigerant circuits to keep that capacity high as it gets colder — rated to roughly -5°F to -15°F depending on the unit. A standard model loses output fast below freezing, which is why the cold-climate spec, not the brand name, is what we confirm before quoting it for Keene.
Sizing at the design temperature, with a backup
Capacity derates as the temperature drops, so a unit rated at its nameplate BTU on a mild day produces less at 5°F. Honest cold-climate sizing runs a Manual-J load calculation and checks capacity at the cold design temperature, not at 47°F. For the few nights that fall below the heat pump's effective range, we plan a backup — your existing furnace or boiler, or electric strip heat — so the home stays covered.
- Cold-climate model. Rated for low-ambient heating, not a standard unit relabeled.
- Design-temp sizing. Manual-J load calc, capacity checked at the cold design temperature.
- Backup plan. Furnace, boiler, or strip heat for the deepest snaps and during defrost.
- Efficiency on the sheet. SEER2 and HSPF2 ratings quoted, not a vague "high-efficiency."
Defrost is normal, not a fault
In cold, humid weather the outdoor coil collects frost, so the unit periodically reverses to clear it — the brief steam you see is defrost working, not the system breaking. We set expectations on this up front. For the full picture, see do mini-splits work in cold New Hampshire winters, and for the rebate math see the NHSaves heat-pump rebate guide. Whole-house coverage usually pairs this with a multi-zone system.