Air Conditioner Reviews, HVAC info and Buyers Guide

The Basics of Installing a Window Air Conditioner

About 6.5 million window air conditioners are sold each year in the US.1 Many are upgrades, but new installations also prevalent. Almost all will be installed by non-HVAC professionals and with a few guidelines, “installation frustration” can be minimized. Here’s how you install a window air conditioner.

Find the Right Unit

A window air conditioner that is improperly sized will not deliver expected results. But finding the right unit is more than just estimating cooling capacity. There are three installation variables to consider:

  • Window location: Where a window is located in relation to the area you wish to cool can influence the unit you purchase. The more centrally located the better, but if the window is off in the corner of a room, you’ll need to think about getting one with a good fan or supplementing airflow with a free standing room fan. The window also has to be accessible, both from the inside and the outside (unless you use a slide out tray) because the unit will require cleaning periodically.2
  • Window size: The size of the window opening governs the maximum dimensions of the unit you install. Openings can be made smaller to fit a smaller air conditioner, but can’t be made larger unless you are willing to remove part of the adjoining wall. The recommendation is to purchase a “curtain kit” with the air conditioner to fill extra space, but these are also available as aftermarket items.3When buying a unit, the rule is to measure twice and then round down. Always expect to need a few inches more. A slide-out carriage is recommended for ease of installation; these are frames that go in the opening and on which the air conditioner rests. They allow you to pull the unit out and into the room for cleaning.
  • Power supply: Most window air conditioners use a 110 volt electrical supply and a normal household outlet. But some larger units do not. If electrical re-wiring is required, this adds considerably to the cost and may be outside a homeowner’s skill set, meaning a profession is needed. Even smaller units can pose a problem if there isn’t an outlet close enough to the window to plug the unit in. Since air conditioners draw considerable current, extension cords are not recommended. However, if an extension cord is used, a larger, appliance rated cord will be necessary. Most manufacturers also recommend a “dedicated” circuit, meaning no other appliances are wired in series with the air conditioner. You can check this by turning off the outlet at the fuse box and seeing if anything else is shut off at the same time.

Choosing the right window:

Since a window unit relies on bridging the gap between outside air and inside, placement is important on the outside too. A unit that is placed in a south-facing window will have its cooling coils exposed to more sunlight and a higher temperature than one in a north-facing window. That can add significantly to the cost of running the unit. Consider adding shade over the unit if a southern window cannot be avoided.

Because cool air tends to fall, a higher window is better than lower, but with good room air circulation, height doesn’t have to be an issue. Most installations will be at hip level and the closer a window is to the interior floor, the less lifting involved in placing the unit.

Installation steps

Step One: Take the time to familiarize yourself with the installation guide provided with the unit. If you do not have a guide or need further information, check out the manufacturer’s website – many have video tutorials and most offer installation guides by model.4

Next, consider having help. Although smaller air conditioner units can be managed by a single individual, window AC units are heavy, as much as 100 pounds (or more)5. The extra set of hands is also helpful when adjusting the unit to fit the window.

Step Two: Before putting the unit in, install any outside brackets or the sliding carriage if you are using one (not the curtain that fills gaps, this comes later) . You may need to work from the outside to do this and sometimes, ladder work is required. Of course, all safety precautions should be followed – another good reason to recruit a friend or helper, they can pass tools out the window or read from the manual as you go.

Step Three: Mount the unit. Some carriages and all outside brackets require attachment to the air conditioner itself. Don’t skip this, it can prevent accidents later. If the “fit” on the bottom edge is not good, you can stuff insulation in the gap or set the unit on sponge rubber. Mounting directly against the window frame has the possibility of generating more noise because of vibration, so a thin pad of rubber material is a good idea if not provided by the manufacturer.

Step Four: Install the curtain. This will fill any gaps on the side of the unit and is held in place by closing the window from above. If you have a window that slides horizontally instead, the opening you need to fill will be above the air conditioner itself. Vertical gaps can be filled in a number of ways, ranging from an expedient piece of cardboard to a professional-looking Plexiglas frame. To see how one homeowner solved the problem, go here.5

Step Five: Troubleshoot the install. Turn the unit on at maximum cooling capacity and highest fan speed to see if the electrical circuit can handle the load. Listen for any vibrations that indicate a loose fit. Check around the unit to see if there are any gaps where outside air may get in – a sunny day and a dark room will help you spot them.

Look over the troubleshooting section of the installation guide to make sure your unit doesn’t have any of the listed problems. Double check that you’ve installed all of the safety hardware, such as sash locks and mounting brackets. Read the maintenance portion of the manual to see that you can access everywhere you need to.

Finally, try out all the functions of the unit, including the remote and those functions you don’t think you’ll need. This serves as a little bit of training in the new equipment and you never know if you’ll want to use some option later.

Other tips

In some areas of the country, home security is a big issue. If you have taken the trouble to secure your home against burglary, you don’t want to create a weak link with an unsecured or unalarmed window because you have an air conditioner in it. For sliding windows, a couple of nails in the window tracks can keep the window from being raised and the air conditioner removed from the outside. You can also install a bracket on the inside that screws into both the base of the air conditioner (use an existing mounting hole) and the wall. This latter trick also keeps someone from stealing the air conditioner itself.

A more complete guide to burglar-proofing a window with an air conditioner can be found here.6

Finally, if a DYI install seems like too much, or if you run into problems, call around – many private air conditioning contractors will install a window unit for the price of a home service call. It costs nothing to ask.

↑ Back to Top

Leave a Reply