How to Install a Window Air Conditioner
A faulty installation can damage your AC—or worse. It can fall out of the window.
Installing a window air conditioner is a sweaty job, so you might be tempted to simply open the window, boost the air conditioner into place, close the window, and hope for the best. Not a good idea, for a number of reasons.
To help you get the job done right, we asked CR’s resident air conditioner expert, Chris Regan, to walk us through the steps for making sure your AC is safely installed (these things weigh 40 pounds or more) and positioned to save energy and avoid air leaks. He has been installing and testing window air conditioners at CR for 15 years and knows a thing or two.
Quick tip: Consider getting a support bracket, especially if you live several floors above street level in an apartment building. These attach to the outside wall directly under the window for your AC to rest on, and cost around $30 to $100. (For more window AC tips if you live in an apartment, read our AC guide for apartment dwellers.)
One other note: You should still read through the manual for your particular AC model. “Do as we do and always follow the manufacturer’s installation instructions, and use the hardware that comes with the AC,” Regan says.
Steps for Securing a Window AC
Step 1: Make Sure It Works!
When you unbox the AC, make sure to remove any foam blocks, tape, and plastic fasteners. And be careful. “The backside of the unit has very thin metal cooling fins that can easily slice fingers,” Regan says. Place the AC on the floor and plug it in to make sure it works. You don’t want to go through all the installation steps just to find out that the thing is a dud.
Step 2: Attach the Panels
Unplug the AC and screw or slip on the two accordionlike side extensions. (These expand so that you can close up the spaces on the sides of the unit once it’s in the window, to keep the cool air inside and the warm air outside.) Most models also come with a separate metal rail that you’ll need to screw on to the top of the unit, which acts as a guide track for the side panels and helps hold the AC in the window.
Best Window ACs From CR's Tests
Which ACs are great at keeping you cool all summer long? Check out the top-performers from our extensive lab tests, organized by the room size you want to chill in.
Best ACs for Small Rooms
(100 to 300 square feet)
For a small bedroom, home office, or guest room, look for an air conditioner with a capacity of 5,000 to 6,500 Btu. You’ll want one with good scores for comfort and noise, and might also consider how well each unit performs under brownout conditions involving extreme heat coupled with low voltage. Here are three top picks to consider.
Best ACs for Midsized Rooms
(250 to 400 square feet)
To cool a bigger or busier room, you’ll want to step up to a midsized air conditioner rated at 7,000 to 8,500 Btu. If it’s for a bedroom, heed our noise scores. Here are three top picks.
Best ACs for Large Rooms
(350 to 650 square feet)
For a living room or family room, you’ll want a large air conditioner with 9,800 to 12,500 Btu, especially if you have an open floor plan. Here are three top choices.