“Should I cover my AC unit in the winter?”
This is quite a frequent question we get in the fall and early winter. Covering an air conditioner in the winter (we are talking about the outdoor unit window AC and heat pumps) does protect the unit but not as most people imagine. We are going to check when it makes sense to cover your AC in the winter and, even more importantly, when you don’t have to cover your AC unit.
In the US Department Of Energy guide for AC maintenance, we have quite a clear-cut answer (but it’s not that simple as we will see):
“Covering the outdoor unit of a central air conditioner will protect the unit from winter weather and debris.” (DOE on covering outdoor AC unit in the winter)
As you might imagine, a covered or uncovered outdoor AC unit faces quite a lot of threats in the winter. Some of these, the AC can handle by itself or the cover won’t help, for others, it is useful to protect your air conditioner by covering it in the winter. The threats include:
- Snow is gathering on the air conditioner.
- Extremely low temperatures in the winter (or extremely high temperatures in the summer).
- Dirt accumulation in the AC unit. This includes small particulates like dust particles, smoke particles, and so on.
- Bigger pollutants get stuck in your air conditioners, including leaves, small twigs, grass, berries, and so on.
- Higher moisture levels can nurture mold growth.
- Icicles falling on the air conditioner from your roof.
- Small rodents like mice, rats, and small birds infest your outdoor ac unit.
Covering an air conditioner during the winter months will help with some of these threats (but not all).
Example: You want to protect your AC from moisture. Should you cover it in the winter to fight moisture? Actually, no. You will do more harm than good to your AC if you cover it in the winter (moisture-wise) because the cover will trap the moisture and increase the likelihood of mold growing in your AC during the winter.
In fact, out of these 7 threats outdoor air conditioner is exposed to, only 4 can be helped by covering your air conditioner in the winter. 2 of them will get even worse if you use a cover on your air conditioner during the winter months.
Let’s break down when you need to cover your AC unit and, essentially, when you should absolutely not use an outdoor AC cover in the winter:
When You Don’t Have To Cover Your AC In The Winter
You probably see many air conditioners covered in the winter. Many air conditioners that are covered actually don’t need to be covered. Namely, homeowners are not getting any significant benefit from covering their AC units.
Here are examples of when it just doesn’t make sense to cover your AC:
- AC cover doesn’t protect your AC against cold temperatures. In the winter, we can experience very cold temperatures (even below -15°F. Covering the air conditioner in below-zero temperatures doesn’t warm it up at all. It is important to note that AC units are built to withstand very low winter temperatures by themselves. Covering it won’t help one bit here.
- AC cover doesn’t help against moisture or mold (quite the opposite is true). High humidity in the outdoor AC unit can cause the mold to grow and damage your air conditioner. There is little we can do to protect against moisture. However, one of the worst things that we can do is cover the AC unit in the winter. That will only help to capture the moisture inside the unit (you will see higher relative humidity levels) and will increase the likelihood of mold growth.
- AC cover doesn’t help again mice, rats, and so on. We might think that covering the AC will prevent rodents from getting inside the unit. The opposite is actually true. In the winter, these rodents are looking for nice cozy spaces. An uncovered AC unit can be a nice retreat. However, a covered outdoor AC can be a little warm heaven to these rodents in the winter. If you cover the AC, you will likely see more mice and rats finding refuge in your outdoor AC unit.
In short, covering the AC in the winter doesn’t help against moisture, rodents, and AC units don’t really need a warming blanket because they are made to endure Eskimo low temperatures.
On the other hand, covering the AC can be very useful if your unit is facing these kinds of threats in the winter:
When You Should Cover Your AC Unit In the Winter
If you face a lot of snow and icing (below freezing temperatures) in your area, it makes sense to cover your AC unit. On top of that, it is also smart to cover your air conditioner in the fall because of all the falling leaves and grass.
Here are the treats to your AC unit that a cover can protect it from:
- Covering AC protects it from freezing (expansion). Snow will gather on the AC unit regardless of whether the AC is covered or not. However, if the snow penetrates the AC and freezes over, that ice will expand and potentially damage your AC unit. There is nothing wrong with snow on top of your AC; all the problems originate from the snow turning into ice and expanding inside the AC unit. If you cover the AC in the winter, you prevent the snow from penetrating inside the AC and protect it from that harmful ice expansion.
- Covering AC protects it from dirt (small particulates). Small dirt particles like dust and small particles (from wildfires) can be partially stopped by a protective AC cover. That’s why it makes sense to cover the AC in the fall (wildfire season) and the winter as well. The less dirt your outdoor AC will accumulate during the winter (especially on the outdoor condensation coils and near the AC compressor), the better.
- AC cover protects your unit from falling leaves, twigs, and grass in the fall. The fall season can be quite dangerous to our outdoor AC units. There are a lot of bigger things that can accumulate inside the AC unit, including leaves, twigs, grass, and so on. If you are cutting grass, for example, the wind can easily carry it to your AC where it accumulates and can cause AC problems in the next cooling season. Covering the AC will not eliminate this problem completely; it will, nevertheless, minimize the accumulation of leaves, twigs, and grass inside your outdoor AC.
- Covers protect AC from falling icicles. In some cases, the outdoor AC unit is positioned directly under the edge of the roof. That’s where icicles can grow in the winter and fall directly on your AC unit, potentially harming it. You cannot stop those icicles from smashing into the AC unit. However, with the AC cover, you are at least limiting their destructive impact (the force is dispersed across the AC over and not all focused on the icicles point).
As you can see, there are quite a lot of benefits of using an AC cover. You will get much of the same benefits if you cover the window air conditioner in the winter as well.
Bottom Line On Using AC Cover Or Not
As we can see, it doesn’t always make sense to use an AC cover. It won’t shield your AC unit from excess moisture or rodents. You don’t really need to use it as a warm blanket around the AC unit in the winter.
However, if you live in an area where you have snow, falling leaves, a lot of grass, and even icicles on the edge of the room, it makes quite a lot of sense to use an AC cover for the outdoor unit.
In short, should you cover your AC in the winter depends a bit on what the AC is surrounded by and the climate (snow, icicles). If you are not completely sure if you should cover your AC in the summer, it is better to do it than not (these covers only cost about $25).
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