How to Install an Air Conditioner in 5 Breezy Steps

Stay cool… you got this

woman sitting on the floor using her laptop
Photo: Cavan Images / Cavan / Getty Images
woman sitting on the floor using her laptop
Photo: Cavan Images / Cavan / Getty Images
Lawrence Bonk
Written by Lawrence Bonk
Contributing Writer
Updated Nov 8, 2022
SKILL LEVEL
Simple
COMPLETION TIME
1 hour
COST
$100–$500
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What you'll need:
TOOLS
  • Scissors
  • Screwdriver
SUPPLIES
  • Appliance cord
  • Foam weatherstrip
  • Window air conditioner
  • Wood block

Dogs are cute, but the dog days of summer are not. The added heat and humidity turn any living space into a drenched mess. That’s where air conditioners come in. If your home lacks the option for a central system, putting in a window unit is the next best thing. Window ACs are budget-friendly, work with many window types, and are relatively easy to install. Just how easy are they to install? You are about to find out. Read on for a step-by-step guide on how to install an air conditioner in your window.

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Prepping to Install a Window AC 

The main step in preparing to install a window AC is to check your windows for integration, in addition to purchasing a correctly-sized air conditioner for that window. Here are tips to do just that. 

  • Buy right: Not all window types do well with window units, and some don’t work at all. This type of AC works best in single- and double-hung windows that slide vertically. Window AC units cost between $140 and $530, on average.

  • Casement windows are an issue: Window units do not integrate well with cranking casement windows and horizontal sliding windows. In these cases, look at rolling portable air conditioners.

  • Don’t worry about width: Most modern window ACs ship with accordion extenders or something similar, so you should not have to worry about the width of your window. Perform measurements in the rare case that you have an extremely narrow or wide window. 

  • Remove storm windows: Beyond making the right purchase, start prepping by removing any storm windows and screens on the outward-facing exterior. 

  • Eliminate debris: While you are there, clear away any brush and debris that might get in the way of the air conditioner later on. A tidy window is a happy window.

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  1. Level the AC and Window

    Your first step is to make sure the AC unit sits level in the window opening. Believe it or not, not all windows are actually level, particularly when measuring from front to back. To solve this problem, add a wood block or two between the windowsill and the future home of the air conditioner. Add one in the front to start and make a measurement, adding another toward the back when necessary.

    Standard 2x4s cut into smaller pieces work well for this, but it truly depends on what is going on with your windowsill and how even it is already.

  2. Add a Weatherstrip

    Woman installing weatherstrip around the window
    Photo: AvailableLight / iStock / Getty Images Plus / Getty Images

    In an ideal world, all of the cool air stays in your home, while the hot air jettisons outside. To assist with this, weatherstrip the window and the area immediately surrounding the AC before going ahead with the installation. Some AC units ship with weatherstripping of some kind, but a standard 1-¼” x 1-¼” foam weatherstrip works great here.

    Cut, peel, and stick the strip as you normally would, making precise cuts so it fits the windowsill to a tee. Affix one strip to the windowsill, another to the bottom of the window, and a final strip on top of the air conditioner.

  3. Place the Air Conditioner

    Before placing the window unit, make sure there are no people, pets, or delicate objects on the ground below where your AC will go. It’s also wise to ask someone to assist you for the actual AC placement. Window AC units are notoriously heavy and easily slip from your grasp, careening to the ground in a thunderous crash. Start by opening the window and liting the air conditioner into the window opening until the accordion wings are completely even with the window jamb. This should center it within the opening. Lower the upper window down on top of the AC and hold it in place. Finish this step by expanding the air conditioner wings so they close the gap on each side.

  4. Affix the AC to the Window

    Air conditioner unit installed in the window
    Photo: Jupiterimages / PHOTOS.com>> / Getty Images Plus / Getty Images

    Affixing the AC to the window is an optional step, as once the AC is correctly placed and the upper window is pushed down into the center, it will hold. If you want extra security, however, affix the AC to the window by inserting some screws through the holes in the wings. This does put holes in your actual window, so exercise caution here, go slowly, and use the correct type of screw. Four screws, two on each side, should finish it off.

  5. Make a Power Connection

    Closeup of a wrapped extension cord on the floor
    Photo: DAVID / Adobe Stock

    Window AC units require a designated 20-amp circuit. If the plug struggles to reach the nearest outlet (window AC plugs are on the shorter side,) feel free to connect it to a heavy-duty appliance cord and run that cord into the outlet. Avoid low-grade extension cords and surge protectors. Give the AC its own spot in the outlet to minimize any chances of overloading the system.

DIY vs. Hiring a Pro to Install an Air Conditioner 

As you now see, this is a DIY-friendly job appropriate for most skill levels. The prep work is minimal and the installation process is fairly universal. However, there are still scenarios that benefit from an experienced hand. Contact a local HVAC specialist if the AC is too heavy to lift and install on your own or if your windows are uniquely-shaped, thus making the installation precarious (to say the least.) You should also consult a pro if you are not sure if your window integrates with window ACs. They will let you know if a portable AC is your best bet. 

Finally, contact a local electrician if there is no suitable power outlet near the air conditioner or if you worry that your current electrical system is not ready for the new appliance.

Frequently Asked Questions

Not only do window units require venting to the outdoors, but the same goes for every type of air conditioner. Heated air has to go somewhere and if you vent anywhere but the outside, you are basically wasting money as your home will heat over time and not cool down. Portable AC units feature a tube that connects to the outside and central units include ducts.

Window AC units use a fair amount of electricity during use, but the usage pales in comparison to central units. As a matter of fact, window units use around a third of the amount of energy as a central AC. On average, a window air conditioner costs between $15 and $40 per month to run, though this depends on a number of external factors.

You don’t have to screw an air conditioner into a window, but it helps secure the AC to the window. Another option besides using screws is to use brackets that hook onto the window, though you need access to the exterior of the window to install these brackets. In other words, apartment residents above the first floor should rely on screws instead of a bracket.

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Learn more about our contributor
Lawrence Bonk
Written by Lawrence Bonk
Contributing Writer
As a technology enthusiast with a professional focus on smart home appliances and accessories, Lawrence Bonk keeps a keen eye on the home improvement innovation space. He is constantly searching for new and convenient ways for homeowners and renters to make the most of their domiciles and has written for publications such as Huffington Post, Engadget, CBS, and many more.

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