About 10 years ago, it was unheard of to use a heat pump in cold climates. Today, the best heat pumps for cold weather can operate at below-freezing temperatures. We are going to look into these low-temperature heat pumps and check which are the best mini split heat pumps for cold climates on the market today.
Namely, mini split heat pumps are exceedingly efficient heating appliances because they don’t create heat out of electricity directly. They use a reverse refrigerant cycle (reversing the flow of R22, R410A refrigerant) to gather available heat from outdoors and bring it indoors. That’s why we see that:
- Best mini split heat pumps can achieve a 400% efficiency (COP = 4) at 47°F.
- Average heat pumps will achieve above 200% efficiency (COP = 2 or higher) at 20°F.
- Best low-temperature heat pumps will achieve 188% efficiency (COP = 1.88) even at 0°F. Check MrCool example further on.
- In below zero temperatures, standard heat pumps COP will fall below 1. However, new mini split heat pumps for cold weather will be able to maintain the efficiency above 100% even at -15°F.
Here is how the DOE describes how good low-temperature heat pumps have become:
“Air-source heat pumps have been used for many years in nearly all parts of the United States, except in areas that experienced extended periods of subfreezing temperatures. However, in recent years, air-source heat pump technology has advanced so that it now offers a legitimate space heating alternative in colder regions.” (US Department Of Energy on Low Temperature Heat Pumps)
As we have pointed out in our article about the disadvantages of heat pumps here, the No. 1 con of heat pumps is low efficiency at very low temperatures. We are talking 20°F, 10°F, 5°F, 0°F, -10°F, and up to -25°F temperatures.
However, as the Canadian HVAC authorities (Canadians have to be better equipped for cold climates) point out very well, “It is important to note that the vast majority of air-source heat pumps have a minimum operating temperature, below which they are unable to operate. For newer models, this can range from between -15°C to -25°C.”
We are going to check the newest 5 heat pumps for cold temperatures with a minimum operating temperature (MOT) from -13°F to up to -22°F. Currently, these are the most energy-efficient mini split heat pumps for cold climates, and the best HVAC choice for both cooling and, importantly, heating.
The whole point of choosing a good heat pump for a cold climate is again neatly laid out by the DOE:
“Cold climate heat pumps (CCHPs) can provide high-efficiency heating in freezing temperatures without producing greenhouse gas emissions and can save families as much as $500 a year on their utility bills.” (DOE of CCHP savings)
You will find a spec-by-spec analysis of the top 5 best low-temperature heat pumps in a comparison table below. The comparison of minimum operating temperatures, COP (Coefficient Of Performance) and hence HSPF ratings (Heating Seasonal Performance Factor), alongside the available BTU output, is essential in order to tell which are high-efficiency heat pumps that work efficiently in cold weather. You can skip to the complete list of the best-spec low-temperature heat pumps, complete with individual reviews here:
Skip To 5 Best Cold Climate Heat Pumps In 2023
However, we think it is essential for everyone looking to buy a cold climate heat pump (CCHP) to understand the basic metrics you should look at before you buy the HVAC unit itself. We will start by looking at the relationship between the effectiveness of heat pumps (COP) and temperature, how the HSPF rating is calculated based on that, and what are the minimum operating temperatures:
Coefficient Of Performance (COP) At Lower Temperatures
The most important specification for the energy efficiency of any heat pump is the COP value (Coefficient Of Performance). COP value simply tells us how much useful heat we can get from ‘burning’ electricity.
Any electric furnace or electric space heater will have a COP value of 1. That means that it will convert 100% of electricity into heat. Heat pumps have an above 1 COP value (up to 4 or 400% efficiency at higher temperatures). That’s because they don’t ‘burn’ electricity to get the heat; they just use it to pump the heat from outdoor to indoors.
Obviously, if the outdoor air temperatures are lower, the COP value or efficiency of the heat pump at low temperatures will be lower as well.
Standard heat pump efficiency will drop to 100% (COP = 1) at about 0°F. At that outdoor temperature, they will have the same energy efficiency as electric furnaces or electric space heaters.
Cold climate heat pumps have similar COP as standard heat pumps at higher temperatures (40°F or above). However, their efficiency is not reduced as radically as for standard units. That means that the best cold climate heat pumps can be used in low temperatures as well. Here is a graph that depicts the COP values of low-temperature heat pumps as a function of temperature:
As we can see, the best mini split heat pumps for cold weather can have an above 200% efficiency at even 0°F.
In the list below, you will see that most heat pump units will have an above 2.0 COP value at 5°F. Example: #3 MrCool DIY 3rd Series units have a 2.31 COP value at 5°F (231% efficiency). #2 Senville AURA Arctic Heat with a minimum operating temperature of -22°F can reach 0.75 COP or 75% at -22°F which is just incredible for such a low temperature.
Let’s have a look at how the heating output is affected by lower and lower temperatures:
Heat Pump Heating Output At Low Temperatures (MrCool Example)
The best way to check how these low-temperature heat pumps behave in very low temperatures is to check measurements in the specs sheet. We are going to use the data in the MrCool specs sheet here (it looks quite complex, we are going to simplify it) to illustrate what is happening with heating output and COP value at very low temperatures.
We are looking at MrCool 12k DIY-12-HP-115B :: DIY-12-HP-C115B, DIY-12-HP-WMAH-115B heating part (top rows). Here are the outtakes:
- At 57°F, we have 14,600 BTU heating output and 1,090W input. COP value at 57°F is 3.92.
- At 53.6°F, we have 14,210 BTU heating output and 1,100W input. COP value at 53.6°F is 3.79.
- At 47°F, we have 13,390 BTU heating output and 1,090W input. COP value at 47°F is 3.60.
- At 44.6°F, we have 12,270 BTU heating output and 1,040W input. COP value at 44.6°F is 3.46.
- At 39.2°F, we have 11,190 BTU heating output and 990W input. COP value at 39.2°F is 3.31.
- At 35°F, we have 10,180 BTU heating output and 920W input. COP value at 35°F is 3.24.
- At 32°F, we have 9,710 BTU heating output and 920W input. COP value at 32°F is 3.09.
- At 24.8°F, we have 9,290 BTU heating output and 910W input. COP value at 24.8°F is 2.99.
- At 19.4°F, we have 8,830 BTU heating output and 910W input. COP value at 19.4°F is 2.84.
- At 17°F, we have 8,360 BTU heating output and 900W input. COP value at 17°F is 2.72.
- At 5°F, we have 6,960 BTU heating output and 880W input. COP value at 5°F is 2.32.
- At 0°F, we have 5,220 BTU heating output and 760W input. COP value at 0°F is 1.88.
- At -5°F, we have 5,060 BTU heating output and 880W input. COP value at -5°F is 1.68.
- At -13°F, we have 4,320 BTU heating output and 870W input. COP value at -13°F is 1.45.
- At -22°F, we have 3,580 BTU heating output and 840W input. COP value at -22°F is 1.25.
As we can see, we come from 392% efficiency at 57°F to 125% efficiency at -22°F.
That we have an above 100% efficiency at temperatures that are as low as -22°F is a tremendous engineering success. You can see that we still have 200% or higher efficiency at single-digit temperatures.
We hope that this MrCool example illustrates well how to think about COP values and why they are so important when picking a good heat pump for cold climates. Let’s look at the second metric that we should also keep in mind:
Minimum Operating Temperature For Heat Pumps
In most cases, you will see a temperature range for heating in the heat pump’s specs sheets. These specs give us an idea of what temperatures we should be using our heat pump for heating. Most often, you will see temperature ranges in 3 categories:
- High heating temperature range: From 5°F to 64.4°F. Heat pump example: Older DAIKIN 17 SEER Series.
- Standard heating temperature range: From -4°F to 75°F. Heat pump example: Mitsubishi MZ-GL12NA 12,000 BTU model.
- Low heating temperature range: From -22°F to 68°F. Heat pump example: This is the best very #1 Cooper & Hunter Hyper Heat 12,000 BTU unit (you can find it in the table below).
Now, as you might imagine, nobody really cares about the higher temperature in this range. What is actually extremely important is the lower temperature. This low temperature is called ‘Minimum Operating Temperature’ or MOT.
As we can see, older mini-split heat pumps will have a minimum operating temperature of about 5°F. Standard units and a bit advanced units like the cited Mitsubishi unit will have an MOT of about -4°F. The best heat pumps for extremely cold climates are the low MOT units that can operate in temperatures as low as 22°F.
Here it is important to mention that (predominantly) manufacturers specify the at what minimum temperature their heat pump should run. That means you might want to take these temperatures with a grain of salt.
Example: #2 Senville AURA Arctic Heat has a 75% efficiency at -22°F and MOT of -22°F. #3 MrCool DIY 3rd Series, on the other hand, has a higher up to 125% efficiency at -22°F but they specify that their heat pumps operate efficiently at -15°F temperature (not -22°F).
Last but not least, you should check several other factors when choosing a low-temperature mini split heat pump:
HSPF Rating, SEER Rating, Heat Pump Size, And Price-Performance
If you have COP values for different temperatures, the HSPF rating will not tell you all that much. In short, the HSPF rating or Heating Seasonal Performance Factor tells you how energy efficient a heat pump is when it comes to heating.
HSPF is primarily used because it is much simpler to understand than COP, and not every company does all the measurements of COP at different (also low) temperatures as we have seen in the MrCool heat pump example above. Namely, the HSPF rating is measured at 47°F average temperature and is listed on EnergyGuide labels. Here is one example of HSPF4 and HSPF5 ratings:
It does tell us how energy efficient a heat pump is but mostly in mild climates (with higher winter temperatures). In cold temperatures, we can learn very little from HSPF. However, even in colder climates, you want to know how your heat pump performs not only in freezing cold winter months (December, January, February). You also want to know how efficiently can your heat pump heat in the fall and spring months. That means that when you are checking out top-rated heat pumps for cold climates, you should also make sure that the HSPF rating is above 8.5.
Similar is true for the SEER rating. SEER rating tells you how well your mini split heat pump will cool in the summer. It is recommended to always go for high SEER heat pumps, with a minimum of 16 SEER rating.
Sizing a heat pump is also important, especially if you know that the heating output at low temperatures will be lower. We have accounted for that drop in COP in the heat pump sizing calculator you can use here. You can usually choose between 9,000 BTU and 36,000 BTU heat pumps. In the table below we followed the 30 BTU of heating output per sq ft general rule of thumb to calculate the maximum square footage, a low-temperature heat pump can cover.
Obviously, you will also want to choose the best performing cold climate heat pump for your buck. Low-temperature heat pumps can be a bit (but not a lot) more expensive than standard heat pumps. Keep in mind that heat pumps with higher BTU outputs as well as SEER ratings should cost more.
With all this in mind, let’s look at which are the best heat pumps for cold weather currently on the market:
Best Heat Pump Mini Splits For Low Temperatures In 2023
| Cold Climate Heat Pump: | 1. Cooper & Hunter Hyper Heat | 2. Senville AURA Arctic Heat | 3. MrCool DIY 3rd Series | 4. Daikin Aurora Series 15k | 5. Pioneer Diamante Series |
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| Minumum Operating Temperature: | -22°F Ambient Cooling | -22°F Ambient Cooling | -15°F Ambient Cooling | -13°F Ambient Cooling | -13°F Ambient Cooling |
| COP At 5°F: | 2.20 (220% Efficiency) | 0.75 At -22°F | 2.31 (231% Efficiency) | N/A | 2.60 At 19°F |
| COP At 47°F: | 3.92 (392% Efficiency) | 2.81 (281% Efficiency) | 3.60 (360% Efficiency) | N/A | 3.20 (320% Efficiency) |
| Available Sizes: | 9k, 12k, 18k, 24k BTU | 9k, 12k, 18k, 24k BTU | 12k BTU | 15k BTU | 9k, 12k, 18k, 24k, 36k BTU |
| HSPF Rating: | 12.0 HSPF | 12.6 HSPF | 10.0 HSPF | 12.5 HSPF | 10.5 HSPF |
| SEER Rating: | 22.5 SEER | 21.5 SEER | 22.0 SEER | 20.0 SEER | 20.0 SEER |
| Coverage Area: | Up To 800 Sq Ft | Up To 800 Sq Ft | Up To 400 Sq Ft | Up To 500 Sq Ft | Up To 1200 Sq Ft |
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1. Overall Best Mini Split Heat Pump For Cold Weather: Cooper & Hunter Hyper Heat
| Minumum Operating Temperature: | -22°F Ambient Cooling |
| COP At 5°F: | 2.20 (220% Efficiency) |
| COP At 47°F: | 3.92 (392% Efficiency) |
| Available Sizes: | 9k, 12k, 18k, 24k BTU |
| HSPF Rating: | 12.0 HSPF |
| SEER Rating: | 22.5 SEER |
| Coverage Area: | Up To 800 Sq Ft |
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| Price: | $$$$ |
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Cooper and Hunter is one of the first companies that managed to create a low-temperature heat pump that could perform efficiently at very low temperatures. Their Hyper Heat series heat pumps (from 9,000 BTU to 24,000 BTU heating outputs) are arguable the best heat pumps you can use if you live in cold climates.
The minimum operating temperature (MOT) of the Cooper & Hunter Hyper Heat series heat pump is incredible -22°F. This is a temperature range far below the standard heat pump heating systems (those can manage to guarantee efficiency at a single-digit temperature at most). -22°F is the lowest temperature a heat pump can operate today.
At 5°F, the Cooper & Hunter Hyper Heat unit can achieve a COP value of 2.20. That means that they have 220% energy efficiency. They are 120% more efficient at 5°F than even the best electric furnaces or electric space heaters. When temperatures in December, January, and February fall to single-digits or even below zero, the high low-temperature COP will ensure you will have relatively low heating costs.
In fall and spring, when the temperatures are a bit higher, you can count on 392% efficiency (COP = 3.92) at 47°F. This, and a very high 12.6 HSPF rating, means that you will be able to keep heating costs as low as possible throughout the heating season as well as in occasional cold falls and cold springs.
In the summer, the Cooper & Hunter Hyper Heat series heat pump will reverse the refrigerant cycle to cooling. Compared to a minimum recommended 14 or 16 SEER rating, this heat pump will be capable of achieving a 22.5 SEER rating. This will further reduce your cooling costs in the summer.
Cooper & Hunter is not as well a known a brand as Daikin or Mitsubishi which can be seen as a con. However, they do offer top-spec low-temp heat pumps at considerably lower prices. Even the 24,000 BTU unit (2-ton) will cost only about $2,000 compared to $3,000+ you would pay for the same-size and not-as-great-low-temp-specs Daikin or Mitsubishi units.
On top of that, the Hyper Heat series include 46°F heating and well as freezing protection.
All in all, Cooper And Hunter Hyper Heat series heat pumps are currently the best heat pumps for cold climates on the market. They have a record low -22°F specified minimum operating temperature, a very high single-digit temperature COP rating, and are the best price-performer in the low-temp HVAC heat pump market:
2. Highest HSPF Rated Heat Pump For Low Temperatures: Senville AURA Arctic Heat
| Minumum Operating Temperature: | -22°F Ambient Cooling |
| COP At 5°F: | 0.75 At -22°F |
| COP At 47°F: | 2.81 (281% Efficiency) |
| Available Sizes: | 9k, 12k, 18k, 24k BTU |
| HSPF Rating: | 12.6 HSPF |
| SEER Rating: | 21.5 SEER |
| Coverage Area: | Up To 800 Sq Ft |
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Senville AURA Arctic Heat is quite an accurately named heat pump. It cannot exactly be used in the Arctic circle where winter temperatures can fall below -40°F but it can very well be used in cold climates of North America, Canada, and so on.
This extremely low-temperature heat pump is one of 2 that has a specific minimum operating temperature of -22°F. The Senville AURA Arctic Heat series units (9,000 BTU, 12,000 BTU, 18,000 BTU, and 24,000 BTU) can achieve a 75% efficiency at -22°F.
At normal winter operating temperatures (47°F; mostly in fall and spring) it has a high 281% efficiency with a 12.6 HSPF rating. However, it shows that the AURA Arctic Heat series is extremely well outfitted for extremely cold weather. Comparatively speaking, many of the best heat pumps for cold weather can achieve a 300% or higher efficiency at 47°F.
When the summer comes along, as the Senville AURA Arctic Heat pumps have to revert the refrigerant-cycle back to cooling, we see a very high 21.5 SEER rating. That means that Senville AURA series (‘AURA’ is used referencing aurora or polar lights) is extremely efficient at very low temperatures and at cooling; it reduces the energy consumption of very low-temperature heating and high-temperature cooling.
Senville also offers very competitive prices given that it is a rising HVAC brand. You are not paying for name recognition; you are paying for the specs.
In short, Senville AURA Arctic Heat series heat pumps can operate in cold climates down to -22°F. It performs a bit less well in milder climates and it has a very efficient cooling system as well:
3. Best DIY Heat Pump For Cold Weather: MrCool DIY 3rd Series
| Minumum Operating Temperature: | -15°F Ambient Cooling |
| COP At 5°F: | 2.31 (231% Efficiency) |
| COP At 47°F: | 3.60 (360% Efficiency) |
| Available Sizes: | 12k BTU |
| HSPF Rating: | 10.0 HSPF |
| SEER Rating: | 22.0 SEER |
| Coverage Area: | Up To 400 Sq Ft |
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| Price: | $$$$ |
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MrCool DIY 3rd Series is one of the best (if not the best) heat pumps for most people living in cold environments. It does not have an extreme -22°F specified MOT rating as Cooper and Hunter, and Senville units, but it still has a measured 125% efficiency even at -22°F. On top of that, it is one of very few DIY heat pumps for low-temperature climates.
Overall, MrCool DIY 3rd Series is many times considered the best modern mini split heat pump. If we check its low-temp heating performance, we can see why it can easily be used in North America and even Canada. Namely, it has a very high 231% efficiency at 5°F outdoor temperature. That is way above most good low-temp heat pumps.
On top of that, it also has a very high 360% efficiency (COP = 3.6) efficiency at standard 47°F winter temperatures. That means it is 260% more energy efficient than any electric furnace or electric space heater. However, it doesn’t have the highest HSPF rating (10.0 HSPF is still above the recommended minimum of 8.5 HSPF rating).
In the summer, the SEER rating is way above the average 14 SEER or 16 SEER. With its high 22 SEER rating, the MrCool DIY 3rd Series heat pumps will provide efficient low-temperature heating as well as save on cooling costs in the summer.
The best part of MrCool heat pumps is that they are made for DIY installation. You don’t actually need that many technical skills to install it yourself; the installation kit and the manual is all you actually need. That means that you can completely avoid $1,000+ heat pump installation costs and the bother of looking for HVAC installers.
All in all, the MrCool DIY 3rd Series is one of the best heat pump options for cold climates. In most locations – considering the MrCool specs – MrCool DIY is a better choice than #1 Cooper and Hunter and #2 Senville AURA unit (not in extremely cold Canadian North). MrCool also offers very affordable prices, especially if you DIY the installation and deduct all the installation costs + labor:
4. Best Daikin Heat Pump For Below Freezing Temperatures: Daikin Aurora Series 15k
| Minumum Operating Temperature: | -13°F Ambient Cooling |
| COP At 5°F: | N/A |
| COP At 47°F: | N/A |
| Available Sizes: | 15k BTU |
| HSPF Rating: | 12.5 HSPF |
| SEER Rating: | 20.0 SEER |
| Coverage Area: | Up To 500 Sq Ft |
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| Price: | $$$$ |
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Daikin is the most well-recognized producer of heat pumps for low-temperature climates. Their Aurora series heat pumps (again, inspired by the polar lights) are specifically designed to withstand low winter temperatures (and retain as much efficiency in below zero temperatures as well). Needless to say, if you want to buy the best Daikin heat pump for cold climates, you go with the Aurora series.
Aurora Series heat pumps by Daikin have a minimum operating temperature of -13°F. That is on par with MrCool DIY mini split heat pumps are is a good indicator that a Daikin heat pump will perform well at sub-zero temperatures.
Sadly, we couldn’t find specifications for COP values for the Daikin Aurora series at regular winter and low winter temperatures. What is comforting are the HSPF ratings. With a high 12.5 HSPF rating, a Daikin Aurora series heat pump can produce 12.5 BTU/hr of heating output for every 1-watt electric input at 47°F. That is way above the 8.5 HPSF average.
The SEER rating – energy efficiency of Daikin Aurora heat pumps for cooling – is 20.0. That is an above-average efficient cooling for a low-temperature heat pump.
All in all, the Aurora series are the best Daikin heat pumps for cold weather. They have superb – but the best – specs. However, Daikin does have a higher price due to brand recognition and a proven long-term operation record of their other HVAC units:
5. Most Versatile Low-Temperature Heat Pumps: Pioneer Diamante Series
| Minumum Operating Temperature: | -13°F Ambient Cooling |
| COP At 5°F: | 2.60 At 19°F |
| COP At 47°F: | 3.20 (320% Efficiency) |
| Available Sizes: | 9k, 12k, 18k, 24k, 36k BTU |
| HSPF Rating: | 10.5 HSPF |
| SEER Rating: | 20.0 SEER |
| Coverage Area: | Up To 1200 Sq Ft |
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| Price: | $$$$ |
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Pioneer Diamante is a series of very cheap heat pumps for cold climates. They also have the biggest capacity range, from the smallest 9,000 BTU heat pumps to the biggest one with up to 36,000 BTU of heating output (that’s equivalent to 3 tons). For example, their 24,000 BTU low-temp heat pump costs less than $1,500 (similar-size units from Daikin would cost about $3,000 or more).
Overall, the Pioneer Diamante has a very low -13°F minimum operational temperature. That is quite low, but as we have pointed out, producers usually specify their MOT themselves.
What really matters are the COP values. At general winter temperatures of 46°F, the Pioneer Diamante series heat pumps have a 320% efficiency (COP = 3.20). That is quite good. However, they fail to report COP values at very low temperatures (like 5°F). We do know that the COP value is 2.6 at 19°F. If you check our MrCool example above, MrCool DIY mini split heat pump has a 2.84 COP at 19.4°F. So, this is a bit lower than MrCool, which is still quite good, given the incredible specs MrCool has.
HSPF rating is 10.5 which is also above-average as is the 20.0 SEER rating.
Of course, the con Pioneer has is that is not as well-recognizable a brand as Daikin or MrCool. But they do offer their heat pumps at quite a discount.
All in all, if you are looking for a good cold climate heat pump on a budget, the Pioneer Diamante heat pump is a good choice and they have quite a versatile portfolio as far as heat pump capacities are concerned:
Overall, we hope you now have a good understanding of what specs you should check when choosing the best heat pump for cold climates. We tried to accumulate as many specs as possible to provide recommendations for heat pumps that perform very well even at sub-zero temperatures. Hopefully, we will see even better and more efficient at low temperatures heat pumps developed in the future.
Engineering triumphs for sure, but unfortunately they still leave deep winter very expensive in cold climates. We routinely have a few weeks per year with daytime temps in single digits, nighttime at single or double negative degrees F. Unless you have some burly solar + storage to go along with that, plus excellent modern home sealing, you’re going to have some pretty wild electric bills in Feb and March. I’ve spent a lot on solar plus efficiency here, dropped my carbon emissions by about 75%, but I can’t afford to heat my entire house at those ratios in deep winter. It’ll be a while before my heating goes electric.
Hi Amy, you are quite right. In very cold climates, it might take a while for electric heat pumps to beat gas furnaces, running cost wise. Nonetheless, heat pump technology is evolving quite rapidly; we now have 400% efficient heat pumps in ideal conditions. If we can get a heat pump with over 3.0 COP at single digit temperatures, that would be absolutely amazing.
What happens to these units if the temperature dips below -22F for a few days? Do they just become much less efficient or do they stop working or, worse, do they break? Thanks!
Hi Tom, that’s a very good question; been wondering that myself, to be honest. The specified lowest running temperature is not at 0.0 COP, right? That means that the heat pump will still run but with awful efficiency. We tried to find what is the COP at the specified lowest temperature (could be a standard 1.0 or 2.0) but this data is sadly not available. If you can find that data point, we would very much appreciate if you can share it here.
Mine just shut off. So you need a backup
A word of caution regarding stand alone air source heat pumps…
Although these offer cheaper first stage heating down to around the freezing point, they should NEVER be depended upon as the sole source of heat in sub-zero climates, especially in full-time human dwellings. They are great for use in barns and workshops. They should certainly be used in homes as they greatly reduce annual heating and cooling expenses during mild to moderate weather; however, they should ALWAYS BE INSTALLED ALONG WITH A SECOND PRIMARY HEATING SOURCE–like a gas, oil or electric heater, a wood stove or a pellet stove-in areas where winter temps fall below -10 degrees C/ 15 F.
Why do this? Because air source heat pumps work differently than other types of heating devices. The colder it gets, the less heat they produce. And it’s not just the QUANTITY of heat that diminishes but the TIME heat is being produced as well. When temperatures drop below freezing heat production drops off almost logarithmically (a very steep curve). Heat pumps have to cycle or defrost to operate. The colder it gets, the more they cycle, the less heat they produce, the less time they are producing it, the colder your home becomes. At some point the units will stop heating completely and wait until the weather warms up to begin functioning again. This is exactly the opposite of what most homeowners expect or want from a home heating system. An honest salesperson should tell you: “This air source heat pump will heat your house really well until around five to ten degrees below freezing. Past that point you’ll need a second source of heat to stay warm.”
Large HVAC manufacturers have accounted for this rapid decline by adding electric heat strips and/or a gas furnace to their package heat pump systems. More exotic heat pump systems use the ground or large containers of fluid as a thermal reservoir, some use an additional compressor that goes into heating mode when the other goes into defrost mode.
These improvements work to generate more heat but cost thousands/tens of thousands more than existing proven non-heat pump technologies. They also require more expensive maintenance and are typically installed when cost is not a factor. Again, this is the opposite of what most homeowners are seeking: They want to LOWER their seasonal heating costs, not raise them.
THE REAL WAY TO REDUCE LONG-TERM HEATING COSTS
Here are a few recommendations for permanently lowering your long term heating and cooling costs, increasing your net value over time and increasing the safety and comfort factor of your home.
1.) First and foremost, build or purchase a WELL INSULATED HOUSE with a WELL INSULATED BASEMENT. Basements can save lives in extreme circumstances because they are surrounded by dirt which has a much higher temperature than sub-freezing air. If new construction is considered, at least build to the HERS “0” or to the Passive House “90% efficiency” standards. Use an architect who knows how to properly use RESNET Construction software so you can design the home for the energy usage you want. If your looking to buy a finished home, search for homes built to the two standards mentioned above, and/or, which were designed by experienced architects using RESNET software. Always know the heating technology used in a home and how old it is before buying it.
2.) Don’t by a lemon—or in this case, a thermally inefficient home that may be difficult to sell in the future and or that drains your bank account each heating season. How efficient can a home be as of 2023? A few contractors in Canada and Germany are building homes that maintain 70 F. indoors at 0 F. outdoors using near the same energy as a hand held hair dryer—and these are NOT small homes. Some are so well insulated they only loose 5 to 8 degrees per 24 hours once the heat is turned off. Building for thermal efficiency and air tightness is the key to staying warm in sub-zero climates. Oddly enough, it’s also the key to maintaining/growing your home’s financial investment in the rapidly changing Real Estate market of the 21st Century.
3.) For cold climates I strongly recommend installing three separate sources of heat in your home: A first stage, a second stage and a third stage. The first stage should be the most efficient and be able to maintain a comfortable indoor temperature with outdoors temps near freezing. Most cold weather quality heat pumps can accomplish this with ease. NOTE: Be sure to look at the heat pumps sold in Norway, Sweden and Germany before making your decision. The second stage should be a reliable existing technology like a gas, oil or electric and should be able to maintain a comfortable indoor temperature when outdoor temps fall into the -30 F range. The third stage should be a super reliable, non-complex heat source like a wood burning stove and should be able to keep at least one indoor room comfortable when outdoor temps drop into the -40 F. range without electricity.
This is not as difficult as it sounds. A popular combination in the Northwest is a modern cold weather heat pump, a Williams Gravity Natural Gas upright wall furnace with millivolt thermostat and a high quality modern Swedish or Norwegian style wood burning stove (or an equivalent type). Note: Both the Williams gas furnace and the wood burning stoves operate without electricity.
Following these recommendations will help to substantially lower your heating costs long term while keeping your family toasty warm under most conditions.
Note: I recommend against building traditional fireplaces and chimneys in modern homes. I DO RECOMMEND using modern high efficiency freestanding wood stoves with an outdoor feed air pipe to the firebox and venting exhaust vertically through the roof or high on a wall. The best units consume wood very slowly, don’t smoke up the neighborhood, operate 5 to 9 hours per loading and do not rely on AC power to function.
Finally, it’s always wise to check with the locals in the area you’re moving to and ask what they prefer to heat their homes with.
A nice article. I notice that, though, you didn’t mention Fujitsu heat pumps or “radiant barrier” insulation techniques. About 10 years ago, I put -15 degree Fujitsu mini splits in my apartments when heating oil prices escalated to over $4 per gallon.
The hardest part was teaching my tenants how to use the heat pumps in order to reduce their need for heating oil.
In my opinion, radiant barrier insulation is the best insulation technique for frame buildings. It is also the most obscure and underused.
Hi Tom, yes, that’s a very good addition. Better insulation is always a good idea, it will reduce the heating BTUs required to heat a home. This is true for all heating and cooling. Here we just wanted to focus on low-temp heat pumps.
Fujitsu is designing better and better units. As far as we can see, their Split Type Super High Power Series units can achieve 2.9 COP at 20F. That’s not bad at all.