How to install a Small Window Air Conditioner

by Team HomeServe |
Open Window

Last summer, I installed my first window air conditioner in my 5th floor walkup. That night, I had a dream (or rather a nightmare) that I didn't secure the unit well enough and it fell out of my window – and crushed the car parked right outside. Luckily, it was just a dream, but it made me start thinking “what if”.


It’s important to know the steps to properly install a window air conditioner. Here’s some advice:

1. Start with the prep work

First things first: Choose your window - ideally near an outlet so you don't have to worry about an extension cord. If you have to use a cord, make sure the packaging says it's one appropriate for an air conditioner or other major appliance.

To ensure the window frame is strong enough to handle the weight of the AC unit, the Home Depot advises repairing any rot or damage before you install. Next, make sure you buy a unit that fits the type of window casing you have in your home. For example, Lowe's points out that most window AC units only work in double-hung windows.

Once you determine the window type, measure the width and height of the opening to make sure you buy an appropriately-sized unit. Wash the window glass inside and out and remove screens or other obstructions from the frame.

Learn More About Home Repair Plans Near You

Finally, enlist a friend, family member or neighbor for help. (Window-unit installation is best done with two people.)

2. Mount the unit

Place the unit on the center of the windowsill and slide out the extensions to fill the empty space. You may need to screw these into place. Follow the manufacturer's instructions to position the unit for proper condensation draining.

3. Secure the air conditioner

Lower the window on top of the window AC unit. Most units come with brackets or clips to further secure it, so follow the manufacturer's instructions for the specific parts. Finally, use weather-stripping to seal the unit.

4. Power it up

Plug in the window air conditioner, press the power button and set the unit to your desired temperature. Pro tip from Home Depot: Keep the cooling power going by cleaning the filter and draining the condensing water regularly.

Next up on the DIY summer-prep list: Install a ceiling fan. For you homeowners out there: maybe next year will be the summer to invest in solar panels or a central cooling system?

Being prepared for home system repairs (like unexpected central AC or cooling system breakdowns in the middle of summer) is a good idea. See how plans from HomeServe can help with the costs of covered repairs.