How Low Can You Go? At What Temperature Does a Heat Pump Stop Working?

By Sarah Stasik

October 19, 2024

When building a new home or upgrading an existing dwelling, there comes a time when you'll need to select your brand-new HVAC system. Depending on where you live, you may need to decide if a heat pump is the right choice.

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If you live in the Midwest, Northeast or Canada, you may also want to know whether extreme cold will negatively impact heat pump efficiency or how cold it can get before a heat pump stops working.

What Is a Heat Pump?

Heat pumps are a part of some HVAC systems. They heat or cool a home by transferring heat from one space to another. For example, they can help cool a home by transferring the warm air from inside the home to the outdoors. They can help heat a home by doing the opposite. The most common types of heat pumps are ground-source heat pumps and air-source heat pumps. The major difference is that ground-source heat pumps transfer heat between the outside ground and the air inside, while air-source heat pumps transfer heat between the air inside and the air outside.

At What Temperature Do Heat Pumps Stop Working Efficiently?

Because heat pumps work in part by drawing from the warmth of air outside, their efficiency drops during cold weather. However, how cold it can get before your heat pump stops working efficiently to provide heat indoors depends on what type of heat pump you have, how old it is and other factors. A ground-source heat pump is more efficient, even at fairly cold temperatures, because the temperature of the ground is more consistent than the temperature of the air outside, for example.

The most efficient modern heat pumps are as efficient as gas furnaces even when outdoor temperatures are 20 degrees Fahrenheit. However, that doesn't mean a specific heat pump will be practical at very low temperatures in your particular house. It's a good idea to consult with an HVAC contractor about what might be best for your home.

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Why Does It Get Too Cold for a Heat Pump?

Many modern heat pumps struggle to efficiently heat a home when temperatures are below freezing for a long period of time. And most don't really work at all at temperatures between 5 and 20 degrees Fahrenheit. The reason for this is common sense: A heat pump can't continue to work efficiently when there's no warmth to draw from. Even a ground-source heat pump will struggle when temperatures are well below freezing or approaching or below 0 degrees Fahrenheit, as at that point, the ground is also quite cold. Heat pumps don't work like other heating equipment, such as furnaces, which means they can't take cold air and make it very warm. While the heat pump might be able to create indoor conditions that are warmer than the outdoors, if the outdoors is 3 degrees Fahrenheit and the indoors gets up to 50 degrees Fahrenheit, that's not necessarily a desirable outcome.

At What Temperature Does a Heat Pump Work Well?

While some heat pumps do work well in cold weather, these HVAC choices tend to be more popular in locations with milder winter weather. States where homeowners tend to choose heat pumps over other options include South Carolina, North Carolina, Alabama, Florida and Tennessee. Most of these locations don't see a lot of days and nights below freezing, indicating that heat pumps may be most popular in areas that don't get extremely cold.

Do heat pumps work in the northeast at all? Yes, they can work in homes in northern and colder climates. However, how much it might cost to heat your home with this type of device depends on other factors, too, including how well your space is insulated, whether you have other heating mechanisms to help support the heat pump and what type of heat pump is installed.

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