When the weather shifts, remembering to winterize your window air conditioning (AC) unit is important. Taking steps to remove it or cover it will prevent damage and ensure optimal performance when you need it again next year during the hot summer months. Follow these steps, and learn how to add proper insulation to your window unit.

If You Can Remove the Air Conditioner Unit:

It is best if you can remove the window unit for winter.

  • Why: It's not a year-round necessity, and removing it during winter will protect it from the damaging effects of the winter elements. By keeping the window closed, you'll create a tight seal between the inside and outside. Good seals promote good energy efficiency. By closing the entire window, you'll see energy savings (and that translates to lower energy bills during the winter months).
  • What to Do: Carefully uninstall the window unit, clean the dirty filters, dust the exterior-facing panels, and store it in a dry and sheltered place.
Air conditioning units in the windows on a brick building.
Learn how to insulate your windows without removing your air conditioner. Credit: Photo by Thomas Layland on Unsplash

If You Can't Remove Your Air Conditioner Unit:

1. Unplug the Unit

  • Keep window air conditioners unplugged during the winter. If you need to keep it plugged in, store the remote control to prevent accidentally activating it during winter.
  • Unplugging it is more energy efficient.

2. Seal Gaps Around the Window Frame

  • Use weatherstripping, polyurethane foam tape, rope caulk, black foam weatherseal, or another flexible foam insulation material to seal gaps between the window unit, the window sash, and the window frame. Any openings can allow cold air leaks to enter your home and warm air to escape.
  • If your window AC model has accordion-style panels, insulate the accordion flaps with foam insulation panels. While the panels are useful, they're not a great barrier against air leaks any time of year.
  • Adhesive insulation products are ideal. Do not use spray foam insulation or a bead of caulk around a window unit. That said, if your window frame itself needs additional sealing, pull out your caulk gun and take care of business.

3. Cover the Outside of the Window Unit

  • Use an outdoor, weatherproof cover to protect the AC unit body from snow, ice, and debris. Not expecting extreme weather conditions? You can also use a breathable fabric layer as additional insulation.
  • Make sure that it's securely fastened but allows for ventilation.

4. Use an Interior Cover

  • Add an interior cover to provide an additional layer of insulation and protection.
  • You can purchase a cover, use foam panels, or use a heavy-duty trash bag secured with duct tape to cover the inside of the AC unit.

5. Elevate the Unit Slightly

  • Elevating a window air conditioner unit helps prevent damage from snow accumulation.
  • Place a wooden or plastic block under the unit to lift it slightly off the window sill.

By taking these steps, you can safeguard your window AC unit from winter weather, reduce energy costs, and extend its lifespan. Always refer to the manufacturer's guidelines for specific recommendations related to your AC unit.