There are pros and cons to covering your air conditioner in the winter. We hear this question frequently, during our service calls on a standard air conditioning unit (non-heat pump). The outdoor portion of the air conditioning system does not operate during the winter, so covering the AC unit will help prevent debris from falling inside of the unit. But, the debris that typically falls into the unit, does not reach condenser coil, which is the part of your AC system that needs to remain free of obstructions, so in general, it is not necessary to cover your air conditioner.
However, because debris can build up over time, leading to corrosion of your AC unit, it is wise to have professional cleaning and maintenance performed by a qualified HVAC technician every year.
If you live in a climate in which heavy accumulation of snow or ice occurs, it is possible for the weight of the snow or the ice to bend the fan blade. In this case, covering the unit can be wise. In a moderate climate, however, this is typically not an issue.
There are a couple of different methods that can be used to cover your AC, if you feel the need. There are covers which wrap completely around the unit from top to bottom. This type of cover is not preferable, as it traps moisture in the unit, potentially leading to corrosion. In addition, this creates a nice comfy residence for rodents!
A better solution is to place a board over the top of the system to will prevent debris from falling into the system, while still allowing the system to “breathe”. Or, there are screens, or caps, manufactured which can be affixed to the top of the air conditioner. These covers can be a proper solution, as long as your AC unit manufacturer guidelines are heeded.
It is imperative to remember that, regardless of cover type (even mesh), the cover needs to be removed before operation in the warmer months. We have seen customers forget that they have covered their AC, and on a warm Spring or Fall day, they decide to run their system, thereby causing their compressor to fail as a result of restricted air flow.
If you have a heat pump system, do not cover your unit, as the heat pump needs to run in both seasons for heating and cooling.
In general, we recommend not covering the AC, and letting it be. The possible negative outcomes that could occur, outweigh the benefits.
If standard yearly maintenance is performed on an air conditioner, this should take care of all concerns that covering the AC would prevent. When in doubt, always consult your trusted heating & cooling technician!