As winter approaches and temperatures take a turn, renters and homeowners alike wonder whether to remove or keep their window air conditioning (AC) units installed. While leaving your AC unit in place seems convenient, there are definite downsides. Not only does it lead to heat loss and drafts in your home, but extra months exposed to the elements can wear on the appliance. That said, if you're intentional about winterizing the unit, it is a feasible option. Just make sure you're doing it right.

Should You Leave Your Window AC Unit in for the Winter?

Leaving a window AC unit installed may seem convenient, but consider the downsides, too. On one hand, you avoid the hassle of removing and reinstalling the unit, but without adequate insulation, gaps, and cracks can lead to heat loss and higher energy bills. We don't need any excuses for higher heating costs during the cold weather season.

Pros:

  • Super convenient. Keeping the unit in place eliminates the need to reinstall it in warmer months.
  • Eliminates the need for storage. Leaving the window air conditioner in place saves on indoor storage space, something at a premium in smaller homes and apartments.
  • Easy. You don't even need tools, just muscles and a few minutes of your time.

Cons:

  • Drafts lead to heat loss. Windows are already weak points for insulation, and an installed unit can allow additional drafts.
  • Drafts can lead to higher heating bills as soon as winter weather arrives. Without weatherproofing, the AC can become a costly entry point for cold air.
  • Increased exposure to wind, rain, and snow. Cold, damp air can lead to corrosion or rust, which has shown to shorten your unit's lifespan.
Window air conditioning unit in an apartment building.
An uninsulated AC unit can cause your home to be drafty. Credit: Photo by Ryan Kwok on Unsplash

Benefits of Winterizing and Weatherproofing Before Bad Weather

Proper winterizing provides several advantages, helping to maintain both indoor comfort and appliance longevity:

  • Enhanced Energy Efficiency: Insulated units prevent cold drafts from increasing heating needs, keeping energy bills manageable. Focus on achieving a tight weather seal.
  • Moisture Protection: A watertight cover for the outdoor unit side shields it from water damage, while interior insulation blocks moisture entry that leads to mold and bad smells.
  • Protects AC Unit Lifespan: Shielding from winter weather reduces the risk of rust and extends the unit’s life.

Two installers maintain a Trane air conditioning unit.
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How to Winterize a Window AC for Cold Weather Protection

If you leave your AC unit in place, winterizing steps will prevent issues from cold drafts, residual water, and moisture. Here’s how to do it effectively:

  1. Close the Vents: Close the AC vents fully to block airflow.
  2. Use a Dedicated AC Cover: A watertight cover is a must. For the outdoor portion, the key step is to make sure you buy a dedicated cover made for window units. They're a breathable fabric and designed to withstand winter precipitation while protecting the condenser coils.
  3. Install Foam Insulation or Weatherstripping: Seal edges around the entire window to reduce drafts and heat transfer during the winter months.
  4. Apply Plastic Sheeting: Plastic sheeting is great if you need an extra layer against cold air. Don't worry, your home will only look like that for a few months... sorry.
  5. Add Interior Insulation: Use a towel or reusable filter inside to help block drafts from residual cold air.
Package of vinyl foam weatherseal self-stick tape.
Use weatherseal around doors and windows to reduce drafts. Credit: E. Fazio

Alternative: Removing and Storing the Window Air Conditioning Unit

If you're fixated on keeping your system in great condition, removing the AC unit for the season is a better idea. Here's why:

  • No gaps, no drafts. Without the unit, the window can be fully sealed.
  • Avoid excessive moisture. Storing it inside prevents buildup from rain or melting snow.
  • Reduce appliance wear and tear. Putting the air conditioner in storage protects it from irreparable damage caused by prolonged cold and any debris issues that the unit may incur.

To safely remove, wipe the unit down with a damp cloth, clean air filters, and make sure all residual water is drained. Store it in a dry, climate-controlled area (even if that's just the bottom of your closet) until warmer weather arrives.