If you’ve heard that heat pumps struggle in the cold, you’re not wrong to think so. Older models really did lose efficiency as temperatures dropped. But the technology has changed. Modern heat pumps are built to keep heating in freezing weather, and cold-climate models in particular perform very well in the cold.
In this guide, we will:
Yes, modern heat pumps are designed to work effectively in cold climates. The Heat Pumping Technologies (HPT TCP) programme, which operates under the International Energy Agency (IEA), notes that modern units maintain high efficiency well below freezing, with advanced cold-climate models operating reliably in ambient temperatures down to -25°C or lower
Rewiring America reported that eight major heat pump companies, including Bosch, Carrier and Daikin, successfully tested their cold climate heat pumps with the Department of Energy in sub zero temperatures.
There are ongoing efforts to accelerate cold climate heat pump innovation. The U.S. Department of Energy has partnered with the U.S Environmental Protection Agency (EPA), Natural Resources Canada (NRCan), and heat pump manufacturers to accelerate the development of cold climate heat pumps to meet consumer comfort and efficiency needs in cold regions of North America.
Heat pumps don’t create heat by burning fuel. Instead, they move heat from one place to another. In cooling mode, a heat pump pulls heat out of your home and releases it outside, just like an air conditioner. In heating mode, it works much like a freezer: a freezer pulls heat out of its very cold interior and releases it into your kitchen, and a heat pump pulls heat out of the cold air outside and releases it into your home. It’s hard to imagine there’s any heat to draw from on a frigid winter day, but there is, even well below freezing.
The home heating - described as the ‘winter heating cycle’ - occurs in a four step process:
A heat pump defrost cycle is an automated feature that melts frost and ice off the outdoor coil during cold weather. Removing this buildup is important for maintaining performance, since any frost can reduce the system’s ability to capture heat from the outside air. Defrost mode is simply the heat pump running in cooling mode for short, periodic cycles to melt the ice and frost.
Yes. Modern heat pumps heat efficiently in cold weather, and many keep performing well below freezing. Most standard models handle typical winter temperatures with no trouble, but their output and efficiency can drop off in extreme cold. Cold-climate heat pumps are designed for exactly those conditions, and they’re the strongest performers when temperatures fall toward 0 to 5°F. If you live somewhere with harsh winters, look for the ENERGY STAR Cold Climate label and speak with your contractor to work out the best solution for you.
In the US, heat pump efficiency is measured by HSPF2 (Heating Seasonal Performance Factor 2) for heating and SEER2 (Season Energy Efficiency Ratio 2) for cooling.
HSPF2 is the current standard for measuring a heat pump’s heating efficiency. It is the total heating output of a heat pump during the heating season divided by the total electricity it consumes. The higher the HSPF2 rating, the more efficient the unit, which can help reduce energy usage and heating costs.
In the US, from January 2023, new split-system heat pumps must be rated at least 7.5 HSPF2, along with 14.3 SEER2 for cooling. Any heat pump legally sold and installed today should meet these requirements. Every six years, the Department of Energy evaluates the effects of energy usage, establishes new minimum efficiency standards and refines the associated testing methods.
Several factors affect efficiency, from insulation and air sealing to thermostat settings and the condition of your ductwork. Sizing is especially important: a system that is too large or too small can reduce efficiency and potentially increase maintenance costs. Regular maintenance, such as cleaning filters and making sure refrigerant levels are correct, also help maintain optimal performance.
To get the most from your heat pump during winter weather, follow these tips:
Set your thermostat to a steady temperature. Thermostat best practices include using ‘HEAT’ mode instead of ‘AUTO,’ since AUTO can cause the system to switch back and forth between heating and cooling. Avoid large overnight setbacks, as these can trigger backup heat and reduce your savings.
If you are in a snowy region, clear snow and debris from the sides and front of the outdoor unit. Use a broom rather than a shovel, and gently brush the snow away.
At what temperature does a heat pump stop working? Many modern cold climate heat pumps work well down to sub-zero temperatures without losing efficiency.
Should I turn off my heat pump in freezing weather? No. It is not advised to turn your heat pump off in freezing weather. Keeping it running maintains a steady temperature and the system will manage defrosting on its own.
Do I need backup heat? You do not usually need backup heat if you have a properly sized cold climate heat pump in a well-insulated home. However, it depends on your climate, home insulation, and system sizing. Always ask your contractor to complete a load calculation (such as a Manual J) to ensure the equipment is accurately sized and to determine whether backup heating is needed.