You don't use your AC unit in the winter, so should you keep it covered, and if so, how? Experts from around the country weigh in.
Should You Cover Your Air Conditioner Condenser In the Winter?
Published on Oct. 29, 2024
If your house has a heat pump, its compressor is in a housing somewhere outside the house. Since a heat pump provides heat in the winter as well as cool air in the summer, there’s no question about covering it because a heat pump works all year.
Before heat pumps came on the scene, however, homes tended to have central air conditioners, which are basically heat pumps that can only transfer heat in one direction — from inside the house to outside. Many homes still have these units, and since they aren’t in service during the winter, there’s a reasonable question about whether you should cover the compressor in the winter.
We asked HVAC pros from around the country for their opinions, and as you might expect, those in the south were less enthusiastic about covering the compressor in winter than those in the north. Sustainability expert Mike Naughton summed it up like this: “Whether or not you should cover your AC unit depends on your specific climate and property. If you live further up North, where it’s prone to heavier snowfall, it would be a good idea to protect your unit with a covering.”
If you do decide to cover your AC compressor unit in winter, what’s the best way to do it? Our experts weighed in.
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What Is an AC Compressor?
An AC compressor is basically an oversized version of the compressor in your refrigerator. It’s a pump that pressurizes a liquid refrigerant inside a condenser coil system. The pressurized refrigerant turns into a gas as it sprays through a valve into a separate set of evaporator coils in the house, which is a process that essentially sucks heat out of the indoor air. The compressor exhausts the heat outdoors as it re-pressurizes the gas to turn it back into a liquid.
The compressor and condenser coils are usually contained in a protective metal housing located somewhere just outside the building. The housing has a network of fins to allow hot air from the compressor to dissipate, and these fins can expose the compressor to snow, moist air and yard debris.
Do You Need to Cover Your AC Compressor?
As Naughton pointed out, whether you need to cover your AC compressor depends on where you live. Glenn Wiseman is a sales rep at an HVAC and Home Services firm in Ottawa, Ontario — which is definitely in a northern climate — and he said: “If your HVAC unit has an outdoor component, it is best to cover it during snow storms. If any ice or snow builds up on the system, remove it immediately to help restore airflow and prevent rust from forming.”
On the other hand, Aaron Traub, an HVAC pro who services the New Orleans area, said: “You don’t always need to cover your outdoor AC unit during winter. Most modern AC units are built to handle the elements.”
HVAC service pro WG Hickman, who lives in Mississippi, added that “covering the outdoor AC unit can even do more harm than good, as covers prevent proper airflow and trap moisture, leading to rust and mold growth.”
If you do cover your AC unit, the best time to do it is in the fall. However, Mark Woodruff, a product manager at Trane Residential, gave this warning: “There are challenges for some of the warmer areas of the country, which may still periodically need cooling during the fall. Homeowners may turn on the AC and forget the cover is on, and that can hurt the air conditioning system.” In other words, prevent damage by remembering to remove the cover before turning on your AC unit.
What’s the Best Way to Cover Your AC Unit?
Tarp? Fabric cover? Plywood? There’s more to consider when making your choice of the way to cover your AC unit than you might have guessed.
For starters, none of the experts consulted for this story recommended covering an AC compressor unit with a tarp. “That can do more harm than good,” said Houston-based HVAC expert David Lewis. “[It could trap] moisture inside, which can lead to rust and mold.” You need a breathable cover, and the best option, according to Woodruff, is an original equipment manufacturer (OEM) cover fitted to the unit and made of quality materials. “Look for unit covers with ventilation flaps or mesh panels to allow for proper air circulation and avoid the risk of mold,” advises Naughton.
“Placing a piece of plywood on top of the unit can help protect it from falling ice or heavy snow,” said Traub. “But I’d be sure to clear it off as needed.” Many experts were in favor of covering the AC unit with plywood, and in many parts of the country, that’s all you need. Place a piece of plywood on top of the housing that is large enough to cover it and secure it with bricks.
Woodruff pointed out, however, that a plywood cover is inadequate in cold climates where salt is used on the roads. “Salt is corrosive and will cause rust, and so keeping salt off of the unit is generally a good thing.” That’s one more point in favor of a fabric cover, but he also notes another point against it: “A cover provides a wonderful warm spot for mice and other critters to live, and they often like to chew on wires and create other issues.”
Winter Maintenance for AC Units
“Whether or not you choose to cover your A/C unit this winter,” said Naughton, “make sure to clear the surrounding area of dirt, debris, twigs, leaves, and animal nests. While most A/C units are built to withstand weather conditions, a build-up of debris can severely impact its efficiency and performance.”
Hickman added: “And here’s an additional tip: Before winter hits, apply a coil-safe anti-corrosion spray to the AC coils to protect them against rust and moisture. Just make sure to use one specifically designed for HVAC systems. If your area gets a lot of snow, elevate the unit slightly by placing it on bricks or pavers, which helps prevent moisture buildup around the base when snow is melting.”
About the Experts
- Mike Naughton is the founder and CEO of Cleveland-based energy brokerage firm Integrity Energy. He has over 14 years of experience in the energy industry.
- Glenn Wiseman RASDT, RHDT is an experienced HVAC technician and the sales manager at Ottawa-based Top Hat Home Comfort Services.
- Aaron Traub grew up around the HVAC industry. He currently owns Benny’s A/C & Heating in Metairie, LA.
- WG Hickman founded Mississippi-based Tri-County Air Services in 2005.
- Mark Woodruff is Senior Product Manager at Trane Residential.
- David Lewis is a seasoned professional in the field of HVAC, plumbing and home services. He is the owner of Mission AC in Houston, TX.
