a heat pump water heat on the left with a man installing the piping on the right, with a emoji cold face symbol in the middle

Heat pump water heaters (HPWHs) pull heat out of the air. If it’s cold outside, you might wonder if these energy-efficient water heaters can do the job. 

Many homeowners consider tankless water heaters and conventional tanks in cold climates, but there’s a big myth about heat pump water heaters that needs to be busted.

In this article, you’ll find out whether or not you can use a heat pump water heater in cold conditions, what temperature is too frigid for an HPWH, and what you should know before choosing one.

Do Heat Pump Water Heaters Work in Cold Climates?

Heat pump water heaters work in cold climates down to 40ºF. Some brands (including A.O. Smith and Rheem) offer heat pump units that function in freezing temperatures. They use electricity to transfer heat from the air into your home, regardless of the external temperature.

Cold climates don’t cause problems for most heat pump water heaters. Energy Star shows these units work at or above 40ºF (4 º Celsius). They work even more efficiently when they’re between 60-70 degrees. You’ll find plenty of energy savings and increased heating capabilities within the optimal range.

However, there are a few challenges that you might encounter along the way.

Difficulties of Heat Pump Water Heaters in Cold Weather

Some obstacles that heat pump water heaters face in cold weather include:

  • Cold temperatures can crack old, worn plumbing – in which case, you’ll end up with leaks. Heat pump water heaters pull heat from the surrounding air, but they can’t work if they leak air through the plumbing. You’ll notice bubbles in the sinks and showers if there’s a crack in the plumbing.
  • You’ll have to keep an eye on the thermostat throughout the colder months – heat pump units’ thermostats sense the external and internal temperatures. So if the thermostat breaks from cold weather, it’ll prevent the water from heating up. This can also happen if the pilot light blows out on gas-powered water heaters.
  • Some heat pump water heaters are only designed for moderate to high temperatures – always check the operating range before installing one in your home. For example, if you choose a high-temperature HPWH, it won’t work below 50ºF. Many companies are designing models with wider ranges, but it’s still worth looking out for.

If you live in a climate that occasionally gets to or below freezing, you likely won’t experience any issues with your heat pump water heater. That being said, those who live in frigid temperatures for several weeks or months should know which temperatures are too low for their appliances.

What Temperature is Too Cold for a Heat Pump Water Heater?

Anything below freezing is often too cold for a heat pump water heater. Most can work optimally between 40-100 degrees. 

Older water heaters might not work well within these parameters, so checking the product’s temperature range is wise. Also, ensure the water doesn’t freeze in the water heater’s plumbing.

A homeowner makes adjustments to the foam insulation attached to the pipes atop his water heater tank

Energy Star claims heat pump water heaters heat slower than traditional water heaters in colder climates. Keep this in mind when using your heating system to manage multiple showers, sinks, etc. 

However, that doesn’t mean they don’t work at all in lower temperatures. Consider running the water at the highest setting, then lowering it once it reaches your desired temperature.

All water heaters have a temperature limit. Most heat pump units have a lower limit than conventional water heaters. They take longer to reach the cap, but it is lower in highly frigid locations. Ramp up the limit to whatever your unit caps out at during the coldest parts of the year.

If there are heat pump water heaters that work a bit better in freezing temperatures, why do so many people choose these appliances? Read on to learn the benefits of using a heat pump water heat when it’s cold outside.

Are Heat Pump Water Heaters Advantageous in Cold Weather?

Heat pump water heaters are worth it in cold weather because they function down to freezing temperatures. In addition, they save a lot of energy, thus keeping more money in your pocket. 

Many heat pump models prevent up to 75% energy loss, regardless of if it’s hot or cold outside. Additionally, you can insulate the plumbing to make it more effective.

Here’s a handful of reasons heat pump heaters are a good choice in cold environments:

  • They last longer than conventional water heaters – heat pump units can last up to 15 years or more. So even if you use them in year-round cold environments, heat pumps are made to withstand harsh conditions for longer periods. They also include much more extended warranties that can be twice as long.
  • You can save money through heat transferring compared to 100% energy generation via fuel burning – heat pump models don’t use a lot of electricity compared to traditional water heaters. Instead, they pull a lot of heat from outside the tank, so you’ll have a large portion of natural energy generation.
  • Reduced heat in summer and prevented excessive humidity throughout the year – since heat pump models absorb heat and transfer it into the water supply, the surrounding air will be a bit colder. It also reduces the ambient humidity, which can be pretty comfortable during cold, soaking winter months.
A diagram showing the components of a heat pump water heater
Courtesy of the Department of Energy
  • Heat pump units don’t have nearly as much metal expansion as water heater tanks – traditional water heaters can make noises, including water knocks and massive shifts. If you get a heat pump water heater, you won’t have to deal with these cold fluctuation sounds, but there will be a different type of noise to be aware of when the heat pump is on with the fan running.
  • Evaporative heating produces fewer carbon emissions in cold conditions – it doesn’t have to use so much energy to heat the air. A lot of water heating comes from the temperature around the water heater. Using less energy means you’re reducing your carbon footprint.

The myth of heat pump water heaters not working in cold climates started because they produce heat from external warmth. In other words, they can heat your water on a hot day. 

That being said, these water heaters use energy to convert external temperatures into heat, regardless of how cold it is outside (within the manufacturer’s suggested limits).

What to Know Before Using an HPWH When It’s Freezing

Before installing a heat pump water heater when it’s frigid outside, check the company’s recommended usage range. While you can use many of these units in cool climates, some work in much colder environments than others. 

Also, don’t forget to consider the natural dehumidifying effects of heat pump water heaters throughout the year.

Keep these five factors in mind when getting a cold-climate HPWH:

  • Most heat pump units won’t work if the water in the plumbing is frozen – heat pump water heaters can’t put heat into the water, so they could end up overheating. However, this happens to almost any water heater. So consider insulating the plumbing to prevent water from freezing during colder months.
  • Proper sizing will increase the operating temperature range – if you choose a water heater that’s too small, it’ll have to work too hard to function correctly when it’s cold. It’s a good idea to base the water heater’s size on how much water you use and how many water sources you have.
An image of a heat pump water heater replacing a less efficient traditional water heater. The two units are standing side by side, part way through the installation process and are not plumbed in.
  • Newer heat pump models have much wider temperature ranges – they can heat down to 40 degrees, but many can go even lower. So it’s essential to have a heat pump unit capable of heating a few degrees above and below your area’s location’s maximum and minimum temperatures.
  • Sealed explains that some heat pump water heaters are designed for colder environments down to 20º F. You could choose these heat pump models if you live in frigid climates. However, they tend to be a bit more expensive since they have more capabilities.
  • You’ll receive more energy savings when it’s hot, but you can still save significant energy in cold temperatures. Unfortunately, you likely won’t be able to retain the same percentage of energy during the winter. Nevertheless, you’ll save more than enough to make it worth it compared to having a conventional water heater.

Some of these issues might seem like setbacks. However, heat pump water heaters save a lot more energy and money in the long run than conventional water heater tanks. Of course, the savings will fluctuate, but you can almost always use a high-end heat pump unit throughout the year in most climates.

The Noise Of The Heat Pump Fan Unit to Be Aware Of

One critical thing to know about heat pump/hybrid water heaters is the noise they make. It has to do with the heat pump/fan unit running at the top of it. They all make some kind of noise, but some are quieter than others.

This means that if the unit makes much noise, you’ll want it away from the living area. This includes the kitchen, living room, bedrooms, and other high-traffic areas. A perfect place can include the garage, basement, or closet far away from the main living areas.

Also, note that sense heat pump water heaters remove heat from the air, which means they emit colder air, like an air conditioner. So any space that it’s in will become cooler, and your heating system will have to work a little bit harder to counteract it.

a blue tesla model 3 on the left with a rheem hybrid heat pump water heater on the right in a garage
In places like Florida, where we install heat pump water heaters in our netzero renovation projects, it’s perfect in the garage. But up north in colder climates, you have to factor in how cold the garage gets throughout the year and the water heater’s capability.

All in all though, the energy savings and efficiency of the heat pump technology should still be well-worth it compared to a conventional water heater.

Final Thoughts

Modern heat pump water heaters work for almost everyone. They’re much more energy-efficient than conventional water heaters, not to mention that they’re a bit quieter. 

So whether you’re getting them for the money savings or the heat transfer technology, these water heaters are more than worth it in nearly any climate.


One Comment

  1. my AO Smith is not operating properly at 45 to 50 degrees in room Im told by manufacturer to switch it to electric until room warms up .model #HPX-50DHPTNE 130 (State Hybrid electric) also was told cold well water could cause issues as well. Any advice on this would be helpful. Planning on putting wall up to create room for water heater and then heating it up so ambient air around heater is 60 to 65

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