Do Heat Pumps Work Below Freezing?


The Modern Heat Pump is Built to Work in Freezing Cold Weather

Heat pump technology is efficient, cost-effective, and environmentally sound, but can a heat pump system perform reliably at sub-freezing temperatures?

Yes — contrary to popular misconception, heat pumps are a practical option in cold climates. Service Legends specializes in installing cold climate heat pump systems for residential homes. We’ve handled more than 1,200 projects by utilizing next-generation air source heat pumps (ASHPs) engineered for harsh winter conditions.

Below, we’ll explain some of the engineering improvements that allow cold climate heat pumps to provide reliable heating with optimal efficiency. If you’re ready for a modern heating and cooling system, an ASHP can provide a quick return on investment — and improved comfort for your home.

How Cold Climate Heat Pumps Work

Air source heat pumps are the most common type of heat pump technology. These systems use ambient air from outside the building as either a heat source or a heat sink.

Heat pumps use the same process as air conditioners when operating in cooling mode. But in heating mode, the systems use outside air to heat a refrigerant. The ASHP compresses the refrigerant to create a hotter gas. The heat energy moves inside the building and is released through an indoor unit (or through ductwork, depending on the construction of the system).

ASHPs provide reliable heating when the refrigerant is significantly colder than outdoor temperatures. In moderate weather, cold climate heat pumps can operate at up to 400% efficiency — in other words, they produce four times as much energy as they consume.

Of course, the colder the weather, the harder the heat pump needs to work to provide heat. Below a certain temperature threshold, the system becomes less efficient. But that doesn’t mean that heat pumps are unsuitable for below-freezing temperatures.

Cold climate heat pumps (also referred to as cold weather heat pumps) have innovative features that allow them to operate efficiently at temperatures below -20°F. Those features include:

Cold-Weather Refrigerants

All air source heat pumps contain refrigerants, and chemical compounds that are significantly colder than outdoor air. Cold climate heat pumps typically use refrigerants that have a lower boiling point than traditional heat pump refrigerants. These refrigerants can continue flowing through a system at low ambient temperatures and draw more heat energy from cold air.

Compressor Design

Over the past decade, manufacturers have refined compressors to reduce the required energy for operation and improve durability. Cold climate heat pumps typically use variable compressors, which adjust their speed in real-time. Traditional fixed-speed compressors are either “on” or “off,” which isn’t always efficient.

Variable compressors can run at a low percentage of their maximum speed in moderate weather, then switch to higher speeds at extreme temperatures. Instead of using an all-or-nothing approach, these inverters draw the right amount of energy to keep indoors spaces at a comfortable temperature.

Other Engineering Optimizations 

While all heat pumps use the same basic process to transfer energy, various engineering improvements can make that process more efficient. Cold climate heat pumps may utilize reduced ambient airflow rates, increased compressor capacity, and improvements to the configuration of the compression cycle.  When the system is right-sized for the application, these types of improvements can greatly reduce energy bills — even in frigid Northeastern winters, when heat pumps operate nearly constantly.

Cold Climate Heat Pumps Vs. Traditional Heating Systems

ASHP heating efficiency is measured with Heating Seasonal Performance Factor (HSPF), a rating that divides the total heating output during the heating season (measured in British Thermal Units or BTUs) by the total amount of energy consumed during that time period (measured in kilowatt-hours). The higher the HSPF, the better the efficiency.

Cold climate heat pumps can deliver an HSPF of 10 or greater — in other words, they transfer significantly more energy than they consume. In the summer months, ASHPs switch to cooling mode and operate as efficiently (or more efficiently) than brand-new air conditioning units.

High-HSPF heat pumps can handle cold weather. At temperatures below -20°F, cold climate heat pumps still provide dependable heat, and many models are 100% efficient at sub-freezing temperatures. Since they consume less electricity in moderate weather, ASHPs cost much less to operate than legacy systems like combustion furnaces and boilers. For homeowners, that means enormous savings over time.

That’s because forced-air systems like natural gas furnaces must generate heat instead of moving heat from place to place. A brand-new, high-efficiency furnace might achieve a fuel utilization rating of 98%, but even an inefficient heat pump system will achieve efficiency of 225% or more.

So, how much could you save by switching to a heat pump? 

Service Legend’s team can provide an accurate estimate for your property, but as a general rule, heat pumps offer an excellent return on investment. According to the Environmental Protection Agency, air source heat pumps can reduce electricity usage for heating by up to 50% compared to electrical furnaces and baseboard heaters, reducing costs by thousands of dollars per year for larger buildings.

On average, Service Legends customers save about 20-70% on their annual heating and cooling bills when switching from traditional forced-air HVAC systems to high-HSPF air pumps.

Cold Climate Heat Pumps: Factors To Consider

At one point, heat pump technology was unsuitable in cold climates. That’s no longer the case: Over the past few years, heat pump adoption has surged in Norway, Sweden, and other Northern European climates with relatively harsh winters.

In the United States, the technology is starting to gain a foothold. The Department of Energy notes that ASHPs offer a “legitimate space heating alternative in colder regions,” and the International Energy Agency reports that annual shipments of heat pumps in the United States expanded from 2.3 million units in 2015 to 3.4 million in 2020.

On average, Service Legends customers save about 20-70% on their annual heating and cooling bills when switching from traditional forced-air HVAC systems to high-HSPF air pumps. If you’re considering an upgrade, here are a few considerations to keep in mind:

  • Cold climate heat pumps are engineered for efficiency, but for optimal savings, systems need to be correctly designed and installed. Factors like insulation and the location of the indoor unit can impact the system’s performance.
  • Ductless heat pumps transfer heat energy directly to indoor spaces, so they’re more efficient than ducted systems. However, for buildings with existing ductwork, a ducted system might be less expensive to install.
  • Energy incentives can cut the cost of installation. Some incentive programs and rebates are exclusive to cold climate heat pumps with a certain HSPF rating. Service Legends’ finance team can help you take advantage of these incentives, ensuring the best return on investment for your project.

Start Saving With A Cold Climate Heat Pump System

By evaluating your home, our Home Comfort Heroes can provide a detailed estimate of your potential savings and exact to-the-penny pricing. Whether you’re retrofitting an old HVAC system or exploring heating & cooling options for a new property, Service Legends is ready to help.

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