Are heat pumps effective in cold climates
By Daniel Kim
A heat pump can be an excellent alternative to a gas or oil boiler, however you may be worried that this type of system won’t heat your home efficiently if you live in a cold climate. In fact, this isn’t the case.
Heat pumps work by using natural heat that can be found in the ground, air or groundwater that surrounds your home. Therefore, unlike other heating appliances, they do not use fossil fuels to warm up your home and can lower CO2 emissions that may otherwise harm the environment. This is making them increasingly popular among homeowners who are conscious of the ecosystem and want to use more renewable energy sources.
But what if you live in a cold climate? In the UK, the temperature can drop to around -10 °C in winter. You may be thinking, how is there enough warmth in the ground or surrounding air to heat your home? We’ve answered this question and many more in this helpful article, so read on to find out more.
How a heat pump works
Heat pumps use the heat in the air or the ground around them as their main source of energy. They use a small amount of electricity to pull this energy out of the surroundings and into a heat exchanger, sometimes known as an evaporator. Within this heat exchanger, the heat is absorbed by a refrigerant, which evaporates and becomes a gas. The refrigerant can absorb heat even in extremely low temperatures of -20 °C, which is why heat pumps are able to work in cold climates.
This evaporated refrigerant is then compressed, which increases the temperature further. The gas can then transfer its heat into your home’s central heating system. When this happens, the refrigerant gradually cools down until it condenses to become a liquid again. This occurs in a second heat exchanger, otherwise known as the condenser. Within the condenser, cooler water from the central heating system can continue to absorb any heat, which is then pumped around your home through any radiators or underfloor heating. Alternatively, it can be used to provide your taps with hot water via a cylinder.
Finally, the cooler refrigerant passes through an expansion valve. The pressure decreases and the refrigerant returns to the evaporator for the whole process to begin again.
How good are heat pumps in cold weather?
Now that you know how a heat pump works, you may still be wondering how the system can take heat from the ground or air when it is below zero degrees.
In the UK, the temperature of the ground doesn’t usually fall below 10 °C. Although this may not feel warm to us, there is still some heat that the heat pump can take to warm up your home. Even with an air source heat pump, there is ambient heat available that can be used. Remember that celsius is a man-made scale and zero degrees doesn’t mean that there is no heat in the air at all. If there was zero heat, the earth would have reached a temperature of -273.
Your heat pump will continue to work in cold weather, as long as you purchase the right one. Every heat pump is different and you will need the right equipment in order to make sure that your home can be heated throughout winter. For the UK’s temperatures, this may not be as big a problem as it could be for some places, such as Canada or North America, where temperatures can drop to -30 °C. As a German manufacturer, Viessmann have tested their heat pumps in the harsh German winter and elsewhere in Europe.
How efficient is a heat pump in cold weather?
Your heat pump won’t be as efficient in cold temperatures as it would be in milder conditions. More electricity may be required to remove the heat from the air, which can result in a lower efficiency.
Heat pump efficiency is measured using Coefficient of Performance (CoP). This is calculated by comparing the amount of input to the amount of output. For example, if an air source heat pump uses one kW of electricity to produce three kW of heat, the CoP is three. The higher the CoP, the better, as it shows your heat pump is more efficient.
If you do live in a very cold climate, you may benefit more from a ground source heat pump. This is because the ground temperature tends to be warmer than the air temperature. Therefore, a ground source heat pump could require less electricity to run and it could produce a greater amount of heat.
With an outdoor temperature of 8.3 °C, your heat pump could achieve around 3.8 CoP. However, if the temperature drops to around -8.3 °C, your heat pump’s efficiency could drop to around 2.3 CoP. If the outdoor temperature drops too low for your heat pump to produce any heat, a backup may be required. This is unlikely to occur in the UK, however, heat pumps in countries such as Canada may need to rely on a backup. This can become expensive,so if you live in an extremely cold climate, a heat pump may not be the most efficient way to heat your home.
Your heat pump will remain efficient for longer if you look after it. You should ensure that your system is serviced every 12 months. Not only does this make sure that everything is running safely, but you’ll also feel happier knowing that your heat pump will be able to warm your home throughout the winter. If you have an air source heat pump, you should clear any debris from the area to prevent the airflow from becoming blocked. This could reduce the heat pump’s efficiency. You may also want to regularly check the filter and change it if needed, any maintenance is best carried out by a qualified engineer.
March 9, 2021
When the north wind blows into Dillingham in the middle of winter, it can plunge well past 15 degrees below zero F on the remote strip of Alaska’s southern coast. On these days, the oil heaters in many of the homes have to run pretty much nonstop to keep people warm.
As you walk through the small fishing town, perched on Bristol Bay’s world-class salmon fishery, you can smell the acrid-sweet scent of wood-burning stoves. But one house stands out from the others: Located on the edge of the town, where spruce forest fades into an endless expanse of frozen, snow-covered tundra, it has no chimney, no fuel tank, no combustion of any kind.
The air-source heat pump that Tom Marsik installed in his house eight years ago was rare for Alaska. Air-source heat pumps take heat from the outside air, run it through a refrigeration cycle to step up the temperature (just like your fridge, but in reverse), and deliver it to a building. Because they rely on “heat” from the outside air, they were not very common in subarctic climates. Yet, for five years, Marsik’s heat pump kept his family warm even on the chilliest days of the year. Thanks to what researchers have learned from systems like this one, heat pumps are taking off in Alaska and other cold places as an alternative to more traditional heating systems like oil and natural gas.
“It’s exciting because they are operating at lower temperatures than they historically have, which means they have the potential to reduce the consumption of fossil fuels in cold climates,” Marsik said. “Helping to push the boundaries of clean energy and develop a sustainable future was important to me, especially in my own house, where we were raising our daughter.”
Today, Marsik lives in Fairbanks and is chief scientist at the National Renewable Energy Laboratory’s (NREL’s) Cold Climate Housing Research Center (CCHRC). Though he does not live in an air-source-heat-pump-heated home anymore, he still spends a lot of time thinking about them, calculating runtimes and defrost cycles, remembering how he would come running downstairs when he would hear a new noise from his own unit, and researching how to make heat pumps work better for more Alaskans, who face a severe climate, lack of infrastructure, and energy bills five times higher than the average American.
Air-source heat pumps are part of a portfolio of solutions that can advance NREL’s mission of making energy more affordable, equitable, and environmentally friendly. Their role, however, varies across the nation’s vast topography of climates, natural resources, and housing types. NREL researchers are looking at how they can help people in cold climates, based on all of those factors and more.
In Alaska, the technology showing the most promise is a ductless heat pump, which includes an outdoor unit that absorbs heat from the air, and an indoor unit on the opposite side of the wall that delivers it to the room. Because there is no distribution system to spread heat throughout the home, ductless systems are well suited for the small, energy-efficient homes often found in Alaska.
“These are getting a lot of buzz largely because of the relatively low installed cost compared to other systems. Because they just blow air to an open space, you don’t have to pay for the cost of a distribution system,” Marsik said.
Of course, there are unique challenges in a place like Alaska. While heat pumps have improved over the past decade, they are still affected by low temperatures: The colder it gets, the harder it is to extract heat, and the less efficient the system is. But just how much does their efficiency drop? To answer this question, Marsik’s team is studying a heat pump inside a 20-below-zero test chamber in their Fairbanks lab. The study will also look at the effect of thermal loading, or the heat demand of the building, on the heat pump’s performance.
“At very cold temperatures, the efficiency is getting relatively low, and at that point it doesn’t typically make sense to use a heat pump anymore,” Marsik said. “And it is often better to use other technologies.”
Understanding the operating limits of heat pumps will shed light on how they can be expanded nationally. There is a much larger market for air-source heat pumps in the Lower 48, where cold-climate residents are also looking for affordable, cleaner ways to heat their homes. One benefit of heat pumps in less extreme climates is that they can provide both heating and cooling, with the simple switch of a valve. NREL researcher Jon Winkler is leading research to see how to get heat pumps into more of these homes.
The subset of housing he focuses on are those with central, forced-air heating—or roughly 35 million U.S. homes. These homes could switch to a heat pump fairly easily because they already have ductwork. The heat pump simply ties into these existing ducts, like a central air conditioner, to provide conditioned air throughout the home. In places with ductwork and high energy costs, heat pumps are especially attractive—like the Pacific Northwest, for example.
“They already have the ductwork, but they’re using electric resistance heaters, which get the lowest possible heating efficiency. Installing a heat pump in these homes makes a lot of sense financially,” Winkler said.
He is currently monitoring a dozen heat pumps in eastern Washington and Montana to gain a refined look at their efficiency. Similar to the Alaska study, Winkler is looking at how the efficiency of a heat pump drops in colder temperatures, and how to appropriately size a heat pump for a home. There is a twist, though: These heat pumps need to be sized to provide both the right amount of heat and air conditioning.
“So, for these homes, what is the optimal heat pump size from an energy efficiency perspective, a cost perspective, and also from a comfort perspective?” Winkler said.
Furthermore, how can heat pumps be combined with other appliances to provide the most benefit?
“Do you need to provide 100% of the heat with that heat pump?” Winkler said. “Or is it more cost-effective to provide 90% of heating with the heat pump and use an electrical backup resistance heater for those few days of the year it gets really cold?”
That is what Marsik did in his Dillingham house, and what millions of other homes in cold climates could do, too. With the study’s results to come, Winkler’s project will create performance maps that show how heat pumps work in different regions of the country where consumers may want them.
While a growing market demand is driving NREL’s research on heat pumps, it is not just about saving money for consumers, Winkler said. One critical piece of moving toward a clean energy economy is to electrify heating—moving buildings to the grid for heating and air conditioning rather than relying on appliances like oil boilers or gas furnaces. This allows green electrons—whether they come from wind, solar, geothermal, or something else—to provide thermal comfort as well as power.
“If we want to be purely renewable, we’re going to have to electrify our home heating use,” Winkler said, “and heat pumps are currently the best way to do that.”
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This is part two of a blog series looking at what you need to know about making the switch to heat pumps.
In part one of this blog, we looked at the basic mechanisms of a heat pump and how they’re able to keep your home comfortable in all seasons. Now, we’re examining common misconceptions about heat pumps – and explaining why these concerns typically no longer apply.
Myth #1: Heat Pumps Don’t Work in Cold Climates
One reason households might be hesitant to switch to a heat pump are concerns that in cold climates, they are inefficient and won’t keep a home toasty. Even just 10 years ago, this concern would be well-founded: as noted in part one of this blog, during winter, heat pumps work by extracting heat from outdoor air and transferring it into a home, so understandably heat pumps must work harder in say, Alaska vs. Florida. You can see this play out in maps of where heat pumps are installed in the U.S.: while they make up about 20% of heating equipment in hot-humid climates, that number falls to 3% of homes in cold climates.
But the technology has come a long way in the past decade. There are now heat pumps that are specifically designed for cold weather, capable of performing well even below -10°F. Don’t believe it? Look no further than Maine, where a program run by the Efficiency Maine Trust has helped achieve one of the fastest uptake of heat pumps in the country. Even in the third coldest state in the country, the heat pumps are proving both effective and efficient at heating, helping Mainers save $812 a year on energy costs compared to a natural gas furnace and up to $2,930 when switching from propane. They are the more efficient method of heating in all but a few hours of the year when temperatures are at their lowest – and Efficiency Maine calculates that the cost benefits of switching to a furnace or boiler during those few hours is just $1.50 a year. So by purchasing a unit that is modern, efficient, and cold-weather-rated, heat pumps can be a very smart choice even in cold climates.
Myth #2: Heat Pumps are Loud
Some people associate noise with heat pumps: back when the technology was newer, the units could make a lot of noise as they switched between various cycles. But options on the market today avoid this problem. For example, ductless heat pumps are one of the quietest HVAC options on the market, with many owners not even able to detect when the unit is on. And even central units can have noise-canceling features installed by an HVAC professional, such as discharge mufflers or insulated compressors. If noise is a big concern of yours when purchasing a heat pump, make sure to complete research on decibel ratings, with quieter central units usually rated below 60 dB.
Myth #3: Heat Pumps Cost Too Much
One of the first things you’ll notice when considering the switch to a heat pump is that they cost more upfront than A/C or a furnace. But there are two important things to remember about that price. One, heat pumps serve more than one function; in fact, they do the job of five different appliances: heaters, air conditioners, dehumidifiers, ceiling fans, and room air filters. If you’re looking to replace both your furnace and A/C, replacing those both separately could cost you $7,000-plus, making the average heat pump installation price of $5,613 suddenly not look too bad (remember, pricing is highly variable depending on factors such as the equipment used, labor charges, etc.).
The second factor to remember is your long-term cost savings by not using as much energy. As noted in part one of this blog, the average U.S. household would save $557 per year on energy costs by making the switch, meaning that the difference between a heat pump and a less efficient HVAC system could be made up within just a few years of switching over – and then continue to offer year after year of savings.
Of course, not everyone can afford to wait a few years to start enjoying those savings. Thankfully, there are many programs across the country offering rebates and incentives to lower that upfront cost. For example, Alliance Associate Chelan PUD offers rebates covering up to 100% of the project cost of a new heat pump installation. Check with your local utility or government organizations to see what rebates are available – and keep in mind that you can get money back by claiming a high-efficiency heat pump installation on your taxes with the Sec. 25C homeowner credit.
So Should I Get A Heat Pump?
As you’ve read in both parts of this blog, heat pumps offer several benefits for residential consumers. Last year, the Alliance’s Active Efficiency Collaborative released a report on beneficial electrification, which is when switching from a fossil fuel device to electric 1) saves consumers money over the long run; 2) enables better grid management; 3) reduces negative environmental impacts; and 4) improves quality of life. So does switching to an electric heat pump meet these criteria? In almost all cases yes: they are so efficient that they can offer households hundreds of dollars per year back in energy savings, they can participate in demand response programs to better manage peak demand events, they reduce carbon emissions in 99% of U.S. households, and they are highly effective at cooling and heating in all climates (unless you plan on spending a lot of your winter in -15°F temperatures).
To take the next step and learn about heat pump options for your home specifically, read up on ENERGY STAR-certified heat pumps!
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Heat pumps are used for heating and cooling in homes throughout the Atlanta area. In our Southern climate, these HVAC systems typically offer energy-efficient comfort throughout the year. However, when temperatures drop too low, you may notice your heat pump struggles. In our most recent blog, Estes Services explains at what temperature do heat pumps become ineffective. For more information on heat pumps, contact us today.
Heating with a Heat Pump
An air source heat pump heats your home by pulling heat from the air outside and transferring that heat into the air circulating throughout your home. Even though it may feel crisp outdoors, there is often ample heat to be found to provide sufficient heating inside your home.
Atlanta winters are mostly mild, which allows heat pumps to operate efficiently in most cases. However, there comes a point when outdoor temperatures drop too low for optimal operation. Heat pumps do not operate as efficiently when temperatures drop to between 25 and 40 degrees Fahrenheit for most systems.
A heat pump works best when the temperature is above 40. Once outdoor temperatures drop to 40 degrees, heat pumps start losing efficiency, and they consume more energy to do their jobs. When temperatures fall to 25 to 30 degrees, a heat pump loses its spot as the most efficient heating option for an Atlanta home.
Even at 25 degrees, your heat pump will still run. The issue at this temperature is that they system will require more energy as it runs because there isn’t enough heat energy in the outdoor air for the heat pump to use in heating your interiors.
How to Heat When Temperatures Are Low
When heat pumps quit working efficiently, many Atlanta homeowners turn to their backup heating systems for warmth. A backup heating system is another type of heating system that is installed to be used during periods where heat pumps do not offer optimal energy efficiency.
Investing in a backup heating system is a smart idea for Atlanta homeowners who don’t want to risk high electricity bills due to heat pumps that struggle amidst the cold. There are a few different system options available, including:
- Electric resistance heating can be added to your home through the installation of heat strips within your HVAC system. The heat strips take over heating once heat pumps stop performing efficiently in cold weather. They aren’t the most energy-efficient option, but they are more efficient than heat pumps at low temperatures. If you don’t have access to natural gas energy at your home, this may be the right backup heating option for you.
- Gas furnaces offer efficient heating during cold periods where heat pumps struggle. If your home has natural gas connections, a gas furnace is likely your most efficient backup heating choice. Gas furnaces do cost more to purchase and install compared to heat strips, but the heating they provide is more efficient and reliable.
Use Backup Heating Wisely
Backup heating systems are an excellent solution when Atlanta temperatures dip toward freezing and heat pumps become less efficient. The key is, they should only be used when temperatures are below 25 to 30 degrees. Running the backup heating system once temperatures are warmer will increase your heating costs.
Your HVAC system should be configured to automatically turn on the backup heating system when it reaches a certain temperature. It should also switch the backup heating system off once temperatures climb above that range, allowing the heat pump to run once more. It is possible to manually switch between systems, but you run the risk of leaving the backup heat on longer than necessary and driving up your heating bills.
Reliable Heating, No Matter What!
Estes Services wants to help you avoid poor heating when outdoor conditions reach temperatures that are cold enough to decrease heat pump efficiency. Contact us to learn more about installation of backup heating options to provide your household with reliable heating, no matter how cold it is outside!
