Winterize window AC units

Prepare your window AC unit for winter storage or cover it if leaving installed.

Why it matters#

Proper winterizing protects your AC from damage, prevents drafts, and ensures it's ready to use next summer.

What you'll need#

Tools#

Screwdriver (if needed for removal)
Vacuum with brush attachment

Materials#

Clean cloths
AC cover (indoor or outdoor type)
Insulation or weatherstripping (if leaving unit installed)

Steps#

1. Decide: remove or leave installed#

Removing is better for the unit and energy efficiency. Leaving installed is easier. If your unit is large or difficult to remove, leaving it may be the practical choice.

2. Turn off and unplug the unit#

Make sure the AC is off and unplugged before doing any work.

3. If removing: Remove the unit from the window#

Unscrew any brackets. Have someone help—units are heavier than they look. Lift straight out and set on a protected surface.

4. Clean the filter#

Remove and wash the filter with soap and water. Let it dry completely.

5. Clean the exterior#

Wipe down the case with a damp cloth. Vacuum any dust from the vents.

6. Let it dry thoroughly#

If any moisture is present (from condensation), let the unit air out for a day before storing.

7. Store in a dry location (if removed)#

Store upright (not on its side) in a dry place like a basement or garage. Cover with a cloth or sheet to keep dust off.

8. Seal the window (if removed)#

Close the window and lock it. If there are gaps from the installation, seal with weatherstripping.

9. If leaving installed: Install covers#

Place an insulated indoor cover over the interior side. Cover the exterior portion to protect from ice, snow, and debris.

10. Seal around the unit (if leaving installed)#

Use weatherstripping or foam insulation around the window opening to minimize drafts. Keep window treatments closed.

Pro tips#

Removing the unit saves energy—even covered, an installed unit is a thermal weak point
If storing, take a photo of your installation brackets and hardware in case you forget the setup
Never run the AC in heating mode—it doesn't work that way and can damage the unit
Spring reminder: check the unit for mouse nests before reinstalling if stored in a garage

Warnings#

Window AC units are heavy—always have a helper when removing or installing
Don't store the unit on its side or back—this can cause oil to flow away from the compressor
Make sure outdoor covers allow some airflow—completely sealed covers can trap moisture

No professional needed for winterizing. However, if your unit is very large (over 12,000 BTU) and mounted through a wall, or you're not comfortable handling the weight, an HVAC technician can remove and store it for you (typically $50-100).