Every autumn this question comes up: should you cover your air conditioner for winter? You've probably seen those AC covers at hardware stores, and now you're wondering if you should be winterizing your unit. For most homeowners with central air, covering your unit can actually cause more problems than it prevents.
Short answer: most people don't need to cover their AC, and shouldn't.
STOP: Do you have a heat pump?
If your outdoor unit runs in winter to heat your home, you have a heat pump, not a cooling-only AC. Heat pumps look identical to AC condensers but operate year-round. Never cover a heat pump. Even a top-only cover can starve the unit of air, damage the compressor, or force the system into expensive emergency heat mode. The advice in this article applies only to cooling-only central AC units that sit idle during winter.
Your outside air conditioning unit is built to handle whatever weather comes its way. Ice, snow, rain, extreme heat: manufacturers design these units expecting year-round exposure to all of it.
So why do AC covers even exist if the units don't need them? We cover our grills, patio furniture, and cars for winter, so it feels like we should cover our AC too. But air conditioners are different from these other items. They're engineered to sit outside in all conditions, and covering them can actually backfire.
That said, there are some scenarios where protection makes sense. Window units are a different story from central AC outdoor units. And even with central air, you might want to shield the top of your unit from specific hazards like falling icicles. We'll get into all of this.
Central air conditioners are designed for outdoor exposure
The outdoor part of your central air conditioning system is commonly called the condenser unit. It's designed for permanent outdoor placement. The housing is made of galvanized steel or aluminum that resists rust and corrosion. The internal components, including the compressor, condenser coils, and fan motor, are built to be weathered.
They install these units in Phoenix where summer heat regularly reaches 110°F. They install them in Minnesota where winter temperatures can drop to -30°F. They install them in Florida where hurricane season brings rain that can dump inches of water in mere hours. The same basic equipment functions in all of these conditions.
The condenser coils in your unit are made from copper and aluminum, which are weather-resistant metals. The electrical connections are sealed and weatherproof. Any refrigerant lines running to your house are insulated.
What about snow sitting on top of your unit? Since the unit isn't running in winter, snow won't affect operation. When spring comes and you turn the AC back on, any remaining snow or ice will melt quickly from the heat the unit generates. However, if snow banks up inside the unit and refreezes repeatedly around the coil base, the expansion can sometimes damage the fins. This is rare but worth watching in heavy-snow areas.
Covering your outdoor unit can cause more problems than it solves
When you wrap your condenser unit in a cover, especially one that goes all the way to the ground, you create an environment that's actually worse for the equipment than open-air exposure.
Moisture is the main issue. Even when it's not raining or snowing, condensation forms when temperatures fluctuate between day and night. In open air, this moisture evaporates. Under a cover, it sits against metal components, accelerating rust and corrosion on parts that would otherwise stay dry. This trapped dampness also encourages mold and mildew growth. When you turn your system on in spring, you might be blowing musty air through your home.
Pests are another problem. Throughout autumn, mice and squirrels are looking for sheltered places to wait out the winter, and a covered AC unit looks warm and inviting. Once they get in, they nest and block airflow, chew on wires, and leave droppings. An uncovered unit doesn't attract their attention since it's too open and exposed.
On a practical note, it's easy to forget that the cover needs to be removed before the AC is turned on. This happens more often than you'd think and can cause the system to overheat and sustain damage. The compressor is the most expensive part to replace, often expensive enough that a new unit makes more sense than a repair.
Window air conditioners are different
Window units are a different category entirely. Part of the appliance sits inside the home while the other part hangs outside. Unlike central AC condensers that are built for year-round outdoor installation, window units are not designed to handle harsh winters in colder climates.
The most effective approach is to remove window units completely during winter months. This eliminates drafts, improves insulation, and lets you store the unit somewhere protected.
However, removal isn't always easy or safe. Larger window units, especially those rated 12,000 BTU and above, can weigh 65 to 80 pounds. They're awkward, have sharp edges, and are often installed in second-story windows. Do not attempt to remove a heavy unit alone. Get help, or if removal isn't practical, insulate it in place instead.
If you can't remove the unit, use an insulated cover designed specifically for window ACs. These are widely available and inexpensive. Make sure to also seal any gaps around the unit with foam panels or weatherstripping. These gaps are the bigger problem: they let cold air flow directly into your home all winter and drive up heating costs.
When a top-only cover makes sense
There are legitimate reasons to protect the top of your central AC unit during winter. If it's located directly beneath a tree that drops limbs, pods, or acorns, a top cover can prevent debris from accumulating inside. If the unit sits in the path of roof runoff, protection can help.
In northern states, the biggest threat often comes from icicles. When icicles form along roof eaves directly above the AC unit, they can break off and fall like daggers. Large icicles can pierce the fan guard, bend fan blades, or puncture the condenser coil, leading to expensive repairs. If your unit is positioned under a roofline where icicles tend to form, a top cover is worth considering.
The key is to cover only the top, not the whole thing. A sheet of plywood weighed down by a brick works well. You can also get mesh covers or commercial top-only covers designed for this purpose. These products block falling hazards while leaving the sides open, preventing the moisture and rodent problems that come with full enclosure.
What to avoid:
- Plastic tarps or sheets that trap moisture
- Covers that extend all the way to the ground
- Any cover that completely encloses the unit
- Bungee cords or straps that could damage the cabinet finish
Important: You must remove any top cover before running your AC. Central air conditioners discharge hot air upward through the fan. A solid cover on top blocks this airflow completely, causing the unit to overheat immediately. This can damage the compressor within minutes. Always check and remove any cover before turning on your system in spring.
Keeping the area around the unit clear is more effective than covering it. Remove fallen leaves regularly, cut back vegetation to at least a two-foot radius around the unit, and make sure snow doesn't bank higher than the top of the unit.
Winter maintenance
For a cooling-only central AC unit, there's no need for a cover. The outdoor unit is fine being left uncovered, and a full cover only invites moisture problems and pests. For window units, either remove them and store them for winter, or cover them with an insulated cover designed for that purpose. If your central AC sits in an area prone to falling debris or icicles, a top-only cover during the off-season makes sense, but remember to remove it before starting the system. Your outdoor unit is more durable than it looks.
