How to Install a Window AC Unit: A Step-By-Step Guide
Installing a window air conditioner is a breeze.
Window air conditioner units are a great way to keep your home cool during the warmer months. Great for smaller spaces or single rooms, window AC units are easy to install and to store while not in use. On top of the convenience, window AC units are an affordable option and do not require ductwork or major renovations. Whether you are installing an AC unit for the first time or just need a refresher, follow this guide for step-by-step instructions on how to install a window AC unit.
What is a Window AC?
A window AC unit is an air conditioner that sits directly in an open window. The panel with the controls sits inside the room. These units work by removing hot air from the room, cooling it, and then blowing cold air back into the room. Air conditioners typically have an internal thermostat that allows you to keep the room at a desired temperature. Window air conditioners come with different features – some have smart features that allow you to control them through an app, some are controlled by a remote, and some are controlled by a panel directly on the unit.
Tip!
Still not sure if a window AC unit is right for you? Take a look at our guide to air conditioner types.
Window AC Installation Overview
Installing an AC unit is easier than you’d think. Use this section to ensure you have everything you need to make sure your project is a success.
Time Required: Under 2 hours
Skill Level: Beginner
Number of People: 2
What You Will Need:
- A window AC unit – be sure to choose the right size air conditioner for the room you are looking to cool. Use our guide What Size Air Conditioner Do I Need? for help.
- Foam weather strip
- Window AC support bracket (optional)
- Tape measure
- Scissors
- Screwdriver
- Power drill (optional)
- L-shaped window locking bracket (optional)
- An appliance or air conditioner extension cord (if needed)
Tip!
Many air conditioners come with an installation kit. Be sure to check what accessories and tools come with your unit so you don’t make unnecessary purchases.
How to Install a Window AC Unit
(Shop this image: window air conditioner, navy curtains and drapes and black curtain hardware .)
1. Assess and prepare your window.
Assess your window’s stability. Look for any damage or rotted wood and make sure the window is sturdy enough to support an air conditioner. If you're concerned about the stability of your window, make any needed repairs first or choose another window. Air conditioner power cords vary in length, so be sure to check the length of your model's cord and choose a window with an outlet in reach.
Decide if you will use a support bracket. A support bracket is an additional piece of hardware that serves as an external platform for your AC unit. A support bracket will take some of the weight of the air conditioner off of the window sash and sill. This will keep your AC unit level, ensure a more secure fit, and help prevent damage to your window frame. You can choose between a support bracket that permanently attaches to your window frame or one that does not require any tools to install and can be easily moved.
Tip!
Make sure to follow the manufacturer's instructions if you do choose to install a support bracket.
2. Measure your window.
Using your measuring tape, measure the window opening. The width of your window opening is most important since you will lower your window sash down to meet the unit once it is placed. Compare your measurements against your desired air conditioner model dimensions and make sure it is not too wide for your window. It is okay if it is narrower than the window – the unit does not need to be as wide as the window since the accordion panels will close the open spaces on each side.
Tip!
Single-hung or double-hung windows that open vertically work best for installing an AC unit. There are also models of air conditioners made specifically for slider or casement windows.
3. Apply a weather strip.
Using a foam weather strip around your window AC unit will create a tight seal to keep cool air in. This will also help keep warm air and excess moisture out of your home.
- Use your vertical window measurements to measure and cut two pieces of the same length of foam weather strip.
- Peel off the adhesive strip and adhere the weather strip to the bottom of your window sash (this will sit on top of the AC once you close the window).
- Attach the other piece of weather strip to the windowsill – the AC unit will sit on top of it.
- You can also measure the height of the accordion panels so you can cut and place a strip vertically where the window frame and panels will meet.
- Many air conditioners come with weather strip material. You can also use non-adhesive foam stripping to insulate as an alternative.
4. Place and secure your air conditioner.
Now it’s finally time to install your air conditioner! Air conditioners are heavy, so it’s best to have a helper assist you with this step.
- Attach the accordion panels to each side of the unit before placing it in the window.
- With a helper, lift the air conditioner and carefully place it on the window sill. Position it to be in the center of the window opening. Make sure your support bracket (if you’ve chosen to install one) is aligned to the back of the unit.
- While holding on to the air conditioner, move it back into place so that the flange (the unit’s bottom guide) is flush against the window stool.
- Once the air conditioner is in the right place, lower the window sash so it is on top of the unit and behind the upper flange.
- Extend the accordion panels to seal off the open spaces on either side of the unit.
- Once these are in place, you can use a screwdriver to secure them to the windowsill so they don’t retract.
- For additional security, you can attach an L-shaped window locking bracket to the upper window sash to prevent the window from accidentally opening. Use a power drill to drill a pilot hole and then attach the bracket with a screw.
Tip!
Be sure to check the manufacturer instructions for your air conditioner model to make sure you are following any specific steps that apply to your unit.
5. Plug in your air conditioner.
Use the cord that comes with your air conditioner model. Plug the cord into a grounded outlet near your window. It’s recommended to plug it directly into the wall. If you do have to use an extension cord, be sure to use an air conditioner extension cord or an appliance extension cord, as standard extension cords can easily get hot or overloaded by major appliances.
