How to Winterize a Window Air Conditioner

A window AC unit.
  • 1-3 hours
  • Beginner
  • 25-50
What You'll Need
Duct tape
Foam insulation
Plastic/vinyl tarp
Garden hose/spray bottle
Vacuum cleaner with attachments
Putty knife

A window air conditioner unit is a lifesaver in the sweltering summer when every day lasts forever and temperatures soar. But when winter sweeps in, your AC unit can really take a beating. It's important to winterize your air conditioner unit so it will be ready in the summer when you start dreaming about those chilly January days.

Winterizing Steps

When you know you're done with your AC unit for the season, go ahead and winterize it before the weather starts to get really cold. If you take a few steps to prepare your air conditioner for the freezing temperatures ahead, your window unit will continue to keep you cool for multiple summers to come.

Step 1 - Turn the Air Conditioner Off

You'll want to open the control panel and turn off your AC unit. This will prevent it from turning on during an unseasonably warm day, which can cause the unit to freeze when winter temperatures normalize. Double check that your air conditioner is in the “off” position. Remember to turn it on again when the summer comes around, or you could spend some anxiety-ridden moments wondering why the unit isn’t kicking on.

Step 2 - Wash the AC Unit

Someone cleaning off an air conditioner frame outside.

Use a garden hose or a large spray bottle to thoroughly clean your AC unit on the exterior side. Wash it with warm, soapy water. Liquid dish soap will work fine for this. After the unit has been cleaned of dirt and debris, rinse it off with plain water. Let the unit dry completely before you move on to the next step.

Step 3 - Clean the Interior

While it’s turned off for the season, take the opportunity to clean the interior side of your AC unit. Dust, hair, and lint have a way of drifting toward air conditioner window units, so they should be cleaned periodically. Remove the front grille of the unit. If the grille doesn't come off with a little bit of pressure, use a putty knife to pop it out of place. Wash the grille in warm, soapy water and then rinse it clean. Now you can use a vacuum cleaner attachment to get dust, hair, and dirt out of the inside of the unit. Stubborn dirt can be removed with a dry scrub brush or wire brush. Use the vacuum to clean below the unit (dust will come down from it), replace the grille once it's thoroughly dry, and you're done.

Step 4 - Insulate Exterior Parts

Surround all exposed exterior pipes with foam. Small sheets of insulating foam are available at home improvement stores. Cut your foam into pieces, and secure it around the pipes with duct tape. You should add some strips of foam around the unit itself where it joins the window. Insulation will protect your unit from freezing during the cold winter. If temperatures drop particularly low in your area, you may consider placing two layers of insulation instead of one.

Step 5 - Cover the Entire Window AC Unit

Next, cover the entire air conditioner unit with plastic or vinyl. This can also be secured with duct tape. Take extra care around the perimeter of your cover to ensure that it is waterproof. Some AC units come with covers, or covers can be purchased for them separately, but using plastic to make a DIY cover also works. Covering your air conditioner this way will protect the unit, but it has the added benefit of insulating the window where the unit is installed. This will keep cold temperatures and breezes out during freezing winter days, which can ultimately help reduce your energy bill.

Step 6 - Maintain You Air Conditioner

A repairman working on an air conditioner.

Physically inspect the exterior of your AC unit every week, and particularly after fresh snow or storms. Remove twigs, brush snow off the unit, and check that the cover is secure. If you find the cover loose or moved, remove it to inspect the unit. Remove debris and water, if necessary, and recover the unit securely.