Running an AC in winter might seem like madness, but there’s a logical explanation.
Should You Be Running Your Air Conditioner in Winter?
The answer is a most definitive yes. In the case of a reversible AC or a ductless heat pump, it makes sense to use it all year round. Ductless heating systems come with many advantages.
Even if your air conditioner is not a reversible one, you may still find some use of it during winters. For example, if your room is getting too stuffy and suffocating due to heating, you could turn on your air conditioner in fan mode and make the room a bit more comfortable.
However, keep in mind that even if you can use your air conditioner during winters, its efficiency will differ from summer. This lowered efficiency can be because although an air conditioner is operable during winters, it is primarily still designed for use when the outside temperature is higher than the indoor temperature.
What Outside Temperature Is Too Cold for Air Conditioners?
Like humans and other home appliances, AC also have a minimum threshold for operation, below which they would not work as intended. This minimum limit for operating temperatures exists for all air conditioners, regardless of their brand, model, or type.
Most manufacturers don’t recommend using AC when the outdoor temperature falls below 60F. Running the AC under 60 degrees will make the refrigerant behave differently, and the air conditioner will not work as intended. If you need to test your HVAC unit, wait until the outdoor temperature is around 60 degrees for at least a few days to ensure there is no ice around the condenser. Also, running the air conditioner in the winter when it’s below this temperature can result in damage to the appliance, such as:
- Freezing of refrigerant coils
- Thickening of lubricant
- Damage to moving parts and bearings
How Do Air Conditioners Keep You Warm in Winter?
To understand how air conditioners work in colder months, you must first know what reversible air conditioners are.
Furnaces and ducted systems will leave a dent in your utility bills, and you might be on the lookout for an alternative that is just as effective in heating your home but not as hard on your pockets. What if, instead of having a separate appliance for heating and cooling, you could use your AC to keep you warm?
That is precisely what a reversible mini-split heat pump does. As a result, you can use the same appliance and enjoy the same energy-saving features throughout the year to keep you cool in the summers and warm in the winters. (If a mini-split isn’t what you’re looking for, there are different types of heat pumps available in the market too).
A regular air conditioner transfers heat from a hot environment (indoors) to a cooler environment (outdoors). This system is all well and good in the summers. But in the winter months, a heat pump extracts heat from the outdoor and transfer it to the indoor. To do that, the air conditioner has to work in reverse.
A little device known as a reversing valve is used in heat pumps to achieve heating functionality. Reversible heat pumps and air conditioners are a nifty invention and are ideal for anyone who wants a unit that cools in the summer while doing the opposite for winter.
Freeze Protection Mode During Winter
Freeze protection is a mode that some air conditioners provide. This mode is also known as minimum heat, low heat, or 8C, depending on your air conditioner. It is useful for places that experience extreme cold in the winter. The AC runs at a low power setting where warm air is continuously introduced. This prevents the room temperature from falling below freezing or reaching near freezing.
This mode helps keep sensitive electronic equipment, water pipes, or paintings safe at a very low operational cost. You can pair your unit with a smart AC controller to control this mode from your phone. This can especially come in handy when your unit is installed in places such as vacation rentals.
Will Running AC in Cold Weather Damage It?
The answer is not as simple as yes or no. Many factors are at play, and running AC in winter is not without risks. With moderately cold temperatures, an air conditioner is perfectly acceptable to run in any mode whatsoever. But when running the AC under 65 degrees, there are certain risks to your air conditioner. Let us go over some of the problems one by one:
Loss of Lubrication
Compressors are an integral part of the air conditioner and need to be in perfect shape to run as desired. Lubricants help the compressor run smoothly and work without any fault. However, this lubricant can thicken in the winter and not perform as expected. Without proper lubrication, the compressor is prone to damage and seizure.
Low Ambient Temperature Sensor
Most modern air conditioners have a low ambient temperature sensor to prevent air conditioner operation during extreme cold. If you try to circumvent this sensor and turn your air conditioner on despite the low temperature, there can be very costly repairs that would need to be done.
As with any mechanical device, a compressor heats up the more it is used. A compressor would need to work overtime to keep the interior warm during extreme cold. This overworking can lead to it getting overheated. Using the air conditioner below the minimum specified temperature can irreversibly damage it, or at best, become a cause for significant AC repairs.
Freezing of Cooling Coils
While an air conditioner is in use, you may observe water dripping from the outdoor unit. This dripping liquid is condensation from the outdoor copper coils. This condensed water can accumulate and freeze over the coils in the winter months. With ice frozen over the coils, circulated air does not heat up, and all you will feel is cold air coming out of the louvers.
Moreover, freezing in the outdoor unit can damage it. Running the air conditioner while frozen can puncture the cooling coils and require a replacement. To prevent this, keep your unit off and allow the ice to thaw for a couple of hours. You can make the process faster by pointing a hairdryer or hot air blower at fans and vents.
Read our detailed guide on AC coil cleaning here.
Measuring Heating Efficiency
Much like how you measure your car’s efficiency in miles per gallon, you measure the heating efficiency of your air conditioner using the Heating Season Performance Factor, or HSPF for short. A higher HSPF translates to a more efficient heating system, resulting in lower energy bills.
HSPF calculations compare the total heat provided by an air conditioner during the heating season with the total amount of electricity used. This ensures that outdoor temperature variations across the whole season are taken into account.
According to the US Energy Information Administration, the minimum HSPF would need to be 8.8 HSPF w.e.f 2023. It used to be 8.2 HSPF before. High-efficiency systems can run up to 13 HSPF, but around 10 HSPF is considered adequate.
To wrap it up, running AC in winter is the sensible choice with modern air conditioners. The benefit is obvious with a reversible air conditioner since you can use the air conditioner unit as a heater. But even with a non-reversible air conditioner, you can get a whiff of fresh air in a stuffy room.
However, it would be best to be careful when running your air conditioner in extreme cold, as the outdoor unit can freeze over. With these checks and considerations in mind, you now know how to run AC winter and are all set to use your air conditioner in winter!
Are these units capable of heating and cooling a 2500 sq ft garage?
Hi, are you referring to mini-splits?
Can or should we put an outside cover on our window air conditioner if we plan to use the heating feature to keep the room warm?
In heating mode, your window heat pump takes heat from the air outside your house and moves it indoors. So, if you put a cover on the outdoor part, your unit will not be able to do its job.
Hey very interesting blog!
It is actually a nice and helpful piece of info.
Confused. The ac coils freeze if it’s below 65degrees outside, but heater coils works fine in below 32 degrees. Do these units heat a home if it’s really cold outside? How cold before they stop working?
Hi Mark, the blog talks about ductless heat pumps that can provide both heating and cooling and work all year round. They work best in heat mode when the outside temperature is above 40F though this varies from manufacturer. Some ductless heat pumps are efficient till 30F and cannot operate below 20 while others can work even at 0 degrees. The HSPF rating can best help determine an air conditioner’s heating capability.
Isn’t there a cold weather kit, a compressor heater, that can be installed to keep the units coils from freezing up when running the ac with the ambient temperature lower than 55 degrees?
Yes, there are low-ambient kits that can be attached to the air conditioners operating at low temperatures in cold weather. However, before attempting to attach the kit on your own, it’s best to consult an HVAC technician and take their professional opinion.
I’ve been running my minisplit during the winter in cool mode to keep my grow room from getting to hot. I haven’t tried running it when the temp goes below 32. Wondering if I can run mini-split in a/c mode during the winter (below freezing temps) to keep my room temperature down. Not the fan mode but on cooling mode.
Hi Dan, running your air conditioner in cool mode below 60 degrees will cause your coils to freeze up. It can also damage other internal components.
There are other ways to keep the grow room temperature under control in situations where you can’t use air conditioning. Refer to our blog for grow tent cooling solutions: https://www.cielowigle.com/blog/grow-room-air-conditioner/
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What about running the ac in cold mode in the winter? Would you have to build a shelter to work both functions as I’m using for growing plants and using a co2 generator with creates heat?
Yes, you can use it in fan mode for air circulation inside your grow room. If you are running it as AC in winter, make sure you only operate it when the outdoor temperature is 60F and above. Air conditioners have a minimum threshold for optimal operation, below which they cannot operate. If you continue to run it below 60F, your AC coil can actually freeze!
What if I take a portable air conditioner and instead of using the cold air output to cool my home and dumping the hot air outside (as I do during the summer), I simply plug the cold output in a new hose and dump it outside while using the hot air to heat my home? Would this work as a heat pump? Or is it dangerous?
Hi Manoh, you should consider using a portable heat pump that provides both heating and cooling and can be used all year round.
Hi Cielo, I have ac portable with 1 single hose only. Can I use it when temprature outside is -5 to -10 celcius to combat my radiator heater? I don’t wanna open the window coz my neighbour is a smoker. I really need this answer. Thanks before!
Hi, air conditioners have a temperature limit below which they won’t work as intended. Most manufacturers don’t recommend using AC when the outdoor temperature falls below 60F. Running the unit in cold weather can result in the freezing of AC coils and damage to the internal parts.
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The electronics in my room make the room 30 celcius in winter when outside it is -50 celcius. I want to cool my room down when outside it is very cold already, but there are no windows in the room. can i run a split ac unit to cool my room down when it is -50 outside?
Hi Robert, most manufacturers don’t recommend using your AC in extreme temperatures as it can pose severe damage to internal components.
Nice article. HSPF calculations compare the total heat provided by an air conditioner during the heating season with the total amount of electricity used. thanks.