Do Heat Pumps Work in Cold Weather? What to Check Before Buying

Heat pumps do work in cold weather, but their output falls as the outdoor temperature drops, which is why ENERGY STAR’s cold-climate test compares output at 5°F with output at 47°F. Below a certain outdoor temperature, the balance point, the house needs backup heat. Models that ENERGY STAR certifies as cold climate heat pumps must still deliver at least 70% of their 47°F heating capacity at 5°F, at a coefficient of performance (COP) of at least 1.75.

What the ratings on a heat pump tell you

The main heating rating is seasonal. HSPF2 is the heating-season efficiency measured under the federal test, and the federal minimum for a split-system heat pump is 7.5 HSPF2, alongside 14.3 SEER2 for cooling (10 CFR 430.32, in force since January 1, 2023).

Seasonal ratings do not show cold-weather output. The Building America Solution Center, run by Pacific Northwest National Laboratory for the U.S. Department of Energy (DOE), notes that the colder it is outside, the harder it is for a heat pump to extract heat, and it says manufacturers’ extended performance data should be used to find capacity at the design temperatures for the home’s location. The practical question for a cold-climate buyer is not whether a heat pump works, but how much of the winter it can carry at a given address.

What “cold climate” means on an ENERGY STAR label

ENERGY STAR’s current heat pump specification, Version 6.2 (revised March 2025), adds a cold-climate designation with its own tests:

• Heating capacity at 5°F of at least 70% of the capacity at 47°F.
• A COP of at least 1.75 at 5°F, meaning 1.75 units of heat delivered for each unit of electricity used.
• A seasonal rating of at least 8.1 HSPF2 for ducted split systems and 8.5 HSPF2 for ductless ones, and at least 15.2 SEER2 for cooling.
• A controls verification procedure confirming the 5°F performance under the unit’s own controls, as it would run in a home.

A standard ENERGY STAR split heat pump, for comparison, needs 7.8 HSPF2 and has no 5°F performance threshold.

How far the technology has gone

DOE has pushed further than the ENERGY STAR floor. In 2021 DOE launched a Residential Cold Climate Heat Pump Challenge whose specification called for a ratio of maximum heating capacity at 5°F to nominal capacity at 47°F of 1.0, in other words full rated output at 5°F, and a compressor that keeps running down to at least -10°F.

DOE lists eight manufacturers committed to the challenge: Bosch, Carrier, Daikin, Johnson Controls, Lennox, Midea, Rheem and Trane Technologies. The challenge describes these units as built to operate with greater capacity and efficiency below 32°F. Its published timeline set laboratory testing in 2022, field testing in the winter of 2022–2023 or 2023–2024, and deployment programs from 2024.

The balance point and backup heat

Every heat pump installation in a cold place has a balance point. The Building America Solution Center explains that when outdoor temperatures are below the balance point, the heat pump cannot fully meet the home’s heating needs without a backup heat source.

The same guide shows the usual arrangements: an electric resistance heating element built into the air handler, a separate backup heating system, or a natural gas dual-fuel system. It also calls electric resistance backup an inefficient form of heat that should be minimized. The energy code limits how it runs. Section R403.1.2 of the 2021 International Energy Conservation Code requires heat pumps with supplementary electric-resistance heat to have controls that, except during defrost, prevent the supplemental heat from operating when the heat pump compressor can meet the heating load.

Sizing a heat pump for a cold climate

Sizing sets the balance point. The Building America Solution Center describes four approaches:

1. Size to the design cooling load. Heating capacity will be significantly undersized, and auxiliary heat covers the gap.
2. Choose variable-capacity equipment sized so that the middle or low end of its range meets the cooling load. Backup heat is still needed.
3. Choose a cold-climate model sized for part of the design heating load, 80% for example, with auxiliary heat for the rest.
4. Size to meet the full design heating load at the local design temperature. This minimizes or eliminates backup heat.

In the third and fourth approaches, the cooling capacity is larger than the cooling load at full output, and the design relies on the equipment modulating down in summer. For humid climates, the same guide points to separate dehumidification or to checking the unit’s latent, moisture-removing, cooling capacity.

For comparing models, the same source points to the Cold Climate Air Source Heat Pump List maintained by Northeast Energy Efficiency Partnerships, a publicly available listing with extended performance data for each model.

Where the federal incentives stand

The federal tax credit is gone. The Internal Revenue Service states that the Energy Efficient Home Improvement Credit, section 25C, “will not be allowed for any property placed in service after December 31, 2025.” The test is the date the equipment is placed in service.

The state-run rebate program funded by DOE for low- and moderate-income households has also changed. DOE Program Notice 26-2, effective May 29, 2026, renamed the Home Electrification and Appliance Rebates program the High-Efficiency Electric Home Rebates (HEEHR) program and removed rebates for replacing gas or other non-electric equipment. It now covers upgrades from existing electric equipment to more efficient electric equipment, plus new construction, and it requires insulation and air sealing before heating and cooling upgrades unless the home already meets a state-set level. Availability depends on the state energy office.

When a professional is needed, and what to ask

Choosing and sizing a heat pump for a cold climate is design work, and the answers belong in writing. Ask:

• What is the design heating temperature for this location, and what heating capacity does the proposed model deliver at that temperature, according to the manufacturer’s extended performance data?
• Is the model on ENERGY STAR’s cold-climate list, and what are its HSPF2 and its COP at 5°F?
• Which of the four sizing approaches does the proposal follow, and where is the balance point?
• What is the backup heat source, and how will the controls keep electric strips from running when the compressor can carry the load?
• Did the load calculation cover both the heating and the cooling seasons?
• Can the existing ducts carry the airflow the new equipment needs, and was airflow measured?
• Does the electrical service need any changes for this equipment?