Ought to You Cowl Your AC Unit within the Winter? Knowledgeable Steerage

Must you cowl your AC unit within the winter? Normally not, if you happen to imply wrapping an out of doors central AC condenser in a full cowl. Lennox says it doesn’t advocate masking an out of doors unit “until you’ve gotten a compelling motive,” and notes that fashionable air conditioners are designed to dwell and function outside. A full cowl, particularly plastic, can lure moisture and provides mice a spot to shelter. A warmth pump that runs in winter should keep unobstructed, and no outside unit ought to ever run whereas lined.

There are just a few instances the place defending the highest of an idle AC unit is sensible. Here’s what the producers and public power applications say, the place the recommendation differs, and what to do as a substitute.

The quick reply from producers

Lennox typically advises in opposition to full winter covers, saying that masking a unit utterly, “particularly with a plastic or vinyl materials,” can do extra hurt than good, and that moisture captured beneath a canopy can result in rust and corrosion. Amana addresses a narrower level: it says by no means to function an out of doors unit whereas it’s lined, as a result of restricted airflow may cause system injury.

That is producer steerage, so it displays what these firms say about their very own gear. Your unit could have totally different directions, so your proprietor’s handbook is the tiebreaker.

Why a full cowl can backfire

Warmth pumps and mini-splits: don’t cowl them

A warmth pump is each your air conditioner and your heater, so its outside unit works all winter. Lennox is direct about it: warmth pumps that run year-round ought to by no means be lined. Our studying: the identical logic applies to a mini-split that heats, however test your handbook.

The NYSERDA warmth pump upkeep reality sheet tells homeowners to maintain the outside unit away from obstructions like leaves, particles, snow, ice and water runoff from the roof, and to trim vegetation so airflow just isn’t restricted. Effectivity Maine warmth pump suggestions says to clear snow drifts away from outside models, preserve shrubs away and take away caught leaves, and notes that warmth pumps defrost robotically.

A storage cowl just isn’t the identical as an overhead shelter. The NYSERDA sheet says a rain and snow shelter might help cut back the work wanted to maintain the unit clear. A shelter or rain cap could make sense when it retains the producer’s required clearances and doesn’t block consumption air, exhaust air or service entry. By no means drape a canopy over an working warmth pump or set a lid immediately on it. For roof runoff, Effectivity Maine suggests a rain cowl or diverter on the roof to direct falling water away, and says that water falling onto the unit can freeze on the fan.

When masking the highest could make sense

Lennox doesn’t say a canopy is at all times improper. It says a canopy could assist if you need safety from falling particles or leaves, and suggests securing a chunk of plywood on high with out limiting airflow. InspectApedia, an impartial reference that partly displays its writer’s opinion, says non permanent safety from uncommon climate, corresponding to hail or a blizzard, could also be affordable for an AC-only unit. A plywood lid is safety from leaves and lightweight particles, not from a big falling department.

Our sensible tip: in case your producer permits a canopy for an AC-only condenser that’s shut down for winter, select a model-compatible high cowl or a securely fitted inflexible lid. Depart the perimeters open, be sure that it can not blow off or block airflow, and keep away from wrapping the gear tightly. If the producer provides an adjunct on your mannequin, affirm whether or not it’s meant for seasonal shutdown or to be used throughout operation, and set up it precisely as instructed.

What to do as a substitute of masking

1. Take away unfastened particles from across the unit. Effectivity Maine warmth pump suggestions says to maintain shrubs away and take away leaves that get caught within the unit, and to keep away from bending the fins. Comply with your handbook, shut the gear off as directed earlier than cleansing, don’t attain via the fan guard, and don’t take away panels.
2. Hold branches and shrubs exterior the producer’s required clearances, together with the house above the unit.
3. Test the unit after every snowfall. SaveEnergyNB says to maintain the outside unit away from snow and notes that buildup can starve the machine of air.
4. Redirect roof runoff so water doesn’t drip onto the unit.
5. Schedule skilled service on the interval beneficial on your system. Our HVAC tune-up information explains what a technician checks.

Snow and ice on the outside unit

A skinny layer of frost on a warmth pump in winter is regular. Service says a lightweight layer of frost, typically lower than 1/4 inch, ought to clear through the unit’s computerized defrost cycle, which generally lasts about 5 to 10 minutes. It says ice thicker than 1/4 inch, a stable coating, or ice that doesn’t clear throughout defrost just isn’t regular, and advises turning off the system and contacting a certified HVAC skilled. It additionally says by no means to chip ice from the coil. If meltwater is refreezing on the coil, Service suggests discovering the supply, corresponding to a leaky gutter.

Window air conditioners

Window models are a special case. ENERGY STAR recommends eradicating a room air conditioner on the finish of the cooling season, if attainable, to reduce warmth loss, or utilizing an appropriately sized cowl throughout winter. Comply with your mannequin’s directions for elimination, storage and masking, and get assist lifting a heavy unit.

See additionally

If you happen to do cowl it, take away the duvet earlier than turning the AC on

Amana says by no means to function an out of doors unit whereas it’s lined. Our sensible tip: set a calendar reminder for the primary heat week, and tie a vivid ribbon to the duvet so it’s arduous to neglect.

Ceaselessly requested questions

Associated studying

Sources

• Lennox, “Ought to I cowl my AC unit within the winter?” (April 2025)
• Amana, “Ought to I cowl my outside unit within the fall and winter?”
• NYSERDA warmth pump upkeep reality sheet (NYSERDA, State of New York)
• SaveEnergyNB, “Sustaining your warmth pump” (NB Energy, Authorities of Canada and Province of New Brunswick)
• Effectivity Maine warmth pump suggestions, “Warmth Pump Consumer Ideas”
• Service, “Warmth Pump Troubleshooting Information”
• ENERGY STAR, “Room Air Conditioners” (U.S. EPA and DOE)
• Effectivity Maine, “Making the Most of Your Warmth Pump”
• InspectApedia, condenser protecting cowl steerage (impartial reference)