Some experts argue that some AC covers actually trap moisture inside your air conditioner for long periods of time which could then lead to the rust as well as the exact same icing problem as when it wasn’t covered. Others point out that covers on AC units keep them dry and relatively clean and free from a steady cold wind - which makes them a perfect place for mice, chipmunks and other critters to snuggle in for the winter and chew your air conditioners wires to shreds.
To summarize, here are the pros and cons of covering your AC unit in the winter months:
Pros to covering your air conditioner:
Keeps your air conditioner coils a little cleaner so it may run a little more efficiently when you use it again
Prevents heavy debris like sticks, branches and other yard waste from blowing into your AC
Helps prevent water from directly resting on your coils and freezing, which could be damaging.
May save on maintenance costs and help lengthen the life of your air conditioner
Cons to covering your air conditioner:
Could trap in moisture if not done properly
Could provide a tempting spot for small animals to nest during winter months
Most AC manufacturers don’t specifically recommend covering the outside unit
Air conditioner units are expensive to replace and even repair should something happen to it. If you’re not going to use air conditioner for a good six months or so out of the year it makes logical sense to close it off from the elements, at least a little bit. Covering your ac unit each year may allow it to last and run a little longer.
Here are some options to consider:
Cover Just the Top of your Air Conditioner: A lot of people choose taking the middle ground with an AC cover. They cover the top of their unit with a piece of plywood and secure it using a heavy brick or rock. This prevents most of the snow and ice from entering your AC unit from the top and it still leaves the sides open for plenty of cool air to blow through, eliminating the trapped moisture problem.
Fully Cover Your Air Conditioner: If you fully cover your air conditioner, you’ll want to take a few things into consideration. Using plastic makeshift AC covers out of things like tarps or large plastic bags are not a good idea because they can easily keep moisture stuck inside for a long time. They will also almost certain rip or blow off during a long winter unless you get pretty creative with your fastening.
If you’re going to go with a full cover then you might want to consider using a specially designed air conditioner cover.