Should You Cover Your AC Unit in Winter?
In most cases, no. Lennox states that modern air conditioners are designed to live and operate outdoors and typically do not need winterization, and it warns that a full plastic or vinyl wrap can trap moisture, invite rust and attract rodents looking for shelter. The one exception worth considering is a top-only cover, such as a piece of plywood or a breathable lid, when ice, snow or branches can fall onto the unit.
That exception matters more in Somerset County than in Pittsburgh. NOAA's 1991 to 2020 climate normals show its Somerset station averaging 96.2 inches of snow a year, more than double the 44.1 inches recorded at Pittsburgh International Airport, with at least an inch of snow on the ground on about 70 days a year. This guide covers why full covers backfire, when partial protection makes sense here, why heat pumps should never be covered, and how to prepare a cooling-only unit for winter.
What Is an AC Cover, and Why Do Full Covers Cause Problems?
An AC cover is a fitted wrap or lid placed over the outdoor condensing unit, the metal cabinet with the fan and coil that sits beside the house. Full covers enclose all four sides plus the top, and that is where trouble starts.
Lennox lists several problems with covering an air conditioner completely, especially with plastic, vinyl or any material that blocks airflow:
Moisture caught under the cover can lead to rust and corrosion on components and the finish.
The humidity that comes with that moisture can damage electronic parts.
Lack of airflow can invite mold and mildew.
Covered units can attract rodents and other small animals looking for shelter from the cold.
Temperatures under a damp cover can drop below the outside air, which can freeze the coils.
Depending on the manufacturer, covering the unit may void the warranty.
The outdoor unit is built to handle weather. Lennox notes that the finishes, structural parts and electronics in current equipment are made to tolerate harsh heat and cold year after year. Wrapping it in plastic adds a moisture problem the unit was never designed to fight.
When Does a Top-Only Cover Make Sense in Somerset County?
Partial protection is reasonable when something can land on the unit from above. Lennox names two situations: units that sit under trees where branches or leaves fall into the cabinet, and cases where an HVAC technician recommends protection based on the location or coming weather.
Somerset adds a third situation: snow and ice sliding off a roof edge directly above the condenser. NOAA's normals for the Somerset station show the ground holding 5 inches of snow or more on about 35 days a year. A unit under an eave sits right where that snow lands when it slides.
Lennox describes safer ways to protect the unit without trapping moisture:
Secure a piece of plywood to the top of the cabinet to block falling debris and reduce ice buildup on internal parts.
Build a shade or extend an awning over the unit, as long as it does not restrict airflow above the fan.
Use a lightweight, breathable cover that will not hold water.
Ask the manufacturer or your technician whether a custom-fitted top protector exists for your model.
Before anything goes on top, Lennox advises inspecting the unit and clearing out any leaves or debris already inside.
Should You Ever Cover a Heat Pump or Mini Split?
Never. Lennox states plainly that heat pumps running year-round should never be covered. As Lennox explains elsewhere, a heat pump moves heat from the outside air into your home, so the outdoor unit needs open air all winter to do its job.
Ductless mini-splits that heat as well as cool fall into the same group. Van Bremen's describes its ductless systems as providing both heating and cooling, which means the outdoor unit works through the winter and needs open air around it.
If you heat with a heat pump, the winter job is keeping snow and ice clear of the unit rather than covering it. The guide to maintaining a heat pump during heavy snowfall walks through that routine, and the Pennsylvania heat pump maintenance guide covers seasonal care.
How Can You Tell If Your Outdoor Unit Is an AC or a Heat Pump?
Before you put anything on the unit, confirm what it is. Three quick checks help:
Watch it on a cold day. If the outdoor fan runs while your heat is on, the unit is heating your home and is a heat pump.
Look at the thermostat. Heat pump thermostats can include an "Emergency Heat" or "EM Heat" setting, the backup mode Lennox describes for heat pump systems.
Read the data plate. The label on the side of the cabinet lists the model number, and the owner's manual or manufacturer's website will say whether that model heats and cools.
If the unit only runs in summer and your home heats with a furnace or boiler, it is a cooling-only air conditioner, and top-only protection is an option.
How Should You Prepare an Air Conditioner for Winter Without a Cover?
Lennox recommends simple fall cleanup as the safest protection. A short routine before the first snow covers most of it:
Turn off power to the outdoor unit at the disconnect box or breaker before touching it.
Clear leaves, grass clippings and sticks from the top grille and from around the base.
Trim shrubs back so air can move freely around the cabinet.
If you add a top-only cover, secure it so wind cannot shift it onto the fan or coil.
Lennox also recommends scheduling regular professional maintenance and changing filters on schedule. A fall visit is a good time for a technician to inspect the outdoor coil and electrical connections, since the system will sit idle for months. The fall HVAC checklist lists the rest of the seasonal steps for the indoor side.
What Happens If You Already Wrapped the Unit?
If a full cover is on now, take it off on a dry day and look for standing water, rust spots, nests or droppings. Leave the cabinet open for a few days so it dries. If you find chewed wiring or heavy corrosion, have a technician look before the system runs in spring, since damaged wiring is an electrical hazard.
Then decide whether the unit needs top-only protection. If no roof edge or tree hangs over it, open air is the better choice. Air conditioners do eventually wear out, and the guide to how long an air conditioner lasts explains what shortens that life.
FAQ
Does snow hurt an air conditioner in winter?
A cooling-only unit is not running in winter, and Lennox notes that current outdoor units are built to handle harsh heat and cold. Lennox does recommend top protection where falling debris or ice from above is a risk.
Can I use a plastic tarp to cover my AC?
Lennox advises against plastic, vinyl or any material that blocks airflow. Those materials trap moisture against the cabinet, which leads to rust and can freeze the coil.
Will covering my air conditioner void the warranty?
It depends on the manufacturer. Lennox says covering a unit may void the warranty for some brands, so check your warranty terms before adding any cover.
Should I cover my heat pump in winter?
No. A heat pump heats your home through the outdoor unit, so it must stay uncovered. Keep snow and ice clear of it instead.
When should I take a winter cover off my AC?
Remove any cover before the system runs for the first time in spring. Air conditioners are designed to run in open air, and a cover blocks the airflow the unit needs.
Do I need an AC tune-up before winter?
Lennox lists a professional inspection as a good way to protect the unit, especially if you plan to add any protection. A fall check also lets a technician spot problems early, so the system is ready when summer returns.
Van Bremen's Heat & Air Keeps Air Conditioners Ready for Spring
Van Bremen's Heat & Air installs, repairs and services air conditioning systems from its Somerset office at 214 Stoystown Rd, serving Somerset, Fayette, Cambria and Westmoreland Counties as well as Morgantown, WV. Its cooling maintenance service covers cleaning and inspection, and the team can tell you whether your outdoor unit needs any winter protection at all. See the cooling services page and maintenance services for details.
Visit Van Bremen's Heat & Air or call (814) 483-1735 today. Contact us for more information.
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