Window Air Conditioners: What to Know Before You Buy

In the market for a window air conditioner? Here are a few key considerations for successfully selecting, installing and maintaining one.

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Invented in the 1930s, window unit air conditioners gained wider use after World War II, becoming a staple in some American homes until the creation of central air conditioning in the 1970s. They’re still a great option for homes lacking central air, or when one or more rooms don’t get quite as cool as the rest of the house.

If you’re in the market, here’s what you need to know about selecting, installing and maintaining a window air conditioner.

How To Choose the Right Window Air Conditioner

The following considerations will affect your decision, although the order of importance depends on you.

Window air conditioner: Sizing and energy consumption

Window air conditioner units are rated in British Thermal Units (BTUs). In general, an air conditioner can cool one square foot per BTU, though various factors impact that calculation. If you live in a particularly hot environment, your windows face south, or your ceilings are higher than eight feet, you may need a unit with a higher BTU rating.

You may be tempted to just buy the unit with the most BTUs. Don’t. An oversized unit will kick on and off too often, wearing it down and consuming excess power. So be sure your window air conditioner is properly sized. A great resource to help with these calculations is the Room AC Sizing Calculator from Energy Star.

Window air conditioner: Features

Apart from sizing and energy efficiency, the primary features of a window air conditioner unit involve convenience. Consider whether these features are important to you:

  • Remote control;
  • Smart phone app;
  • Easily accessed filters;
  • Variable speed settings;
  • Fan-only option.

Window air conditioner: Pricing

Window air conditioner prices are driven by the size and features of the unit. Typically, a bare-bones unit will cost around $150, while a fully-tricked-out model can cost $500 or more. For most users, the sweet spot that balances power and features will be $250 to $300.

Window air conditioner: Unique considerations

Every building has unique features that need to be considered when selecting and installing any window air conditioner. Variations can be limitless, but common factors include:

  • Unusual window sizes: Select a window air conditioner that comes as close as possible to filling the window width. If you can’t find an exact match, pick up a foam side panel kit like this one from Air Jade.
  • A deck or patio directly below the window: If this is your situation, the window air conditioner’s condensation will likely drip on any furniture (or people!) below. Some units allow a garden hose or plastic tube to redirect the condensation. Or consider a portable air conditioner instead.
  • Security concerns: This is most often an issue with first-floor installations. It’s possible for a window air conditioner unit to be stolen or simply pushed in, allowing a burglar to break into the home. Lower this risk by securing the unit at multiple points, or by installing it in an inaccessible or hard-to-reach location.

Window air conditioner: Installation

Window air conditioner installation is relatively straightforward, and well within the skill set of any DIYer. Here are a few factors to consider:

  • Stability: Larger units may need reinforcement in the window frame, or even an exterior ledge to support the weight of the compressor.
  • Air penetration: Many window air conditioners are not as wide as the windows where they are being installed, and the gap between the air conditioner and window frame will need to be bridged in some way. Some units use expandable wings, while others require additional materials to close that gap, like the foam panels mentioned above. Either way, that window seal won’t be airtight. It’s a good idea to use weatherstripping to reduce air penetration and keep the cold air where it belongs — inside your house!
  • Condensation: All air conditioners create condensation. Most of it falls to the ground outside or collects in a tray and evaporates. It’s essential that the window air conditioner unit be installed at a slight downward incline and never with a tilt to the interior. If that water drains onto the window frame, you’ll have serious rot problems.
  • Electrical supply: Most window air conditioners use standard 110-volt electrical service, though some require 220 volts service. If 220-volt service is not available where you want to install the unit, be sure to buy one that works with 110-volt service.

Window air conditioner: Maintenance

The good news is that window air conditioners are remarkably low-maintenance. Like all air conditioners, you’ll need to change the filters on occasion. These are normally located behind the front grill — simply slide out to the top, bottom or sides. Most window AC filters can be hand-washed and returned to the unit once they’ve dried.

The only other maintenance issue is cleaning debris off the exterior of the unit. If the window air conditioner unit is left in place during the off-season, consider securing it with a cover to prevent animals from building a nest. If it’s taken down over the winter, that’s a great opportunity to give it a good cleaning.

Dan Stout
Ohio-based freelance writer and author Dan Stout is a former residential remodeler, commercial site supervisor and maintenance manager. He’s worked on nearly all aspects of building and DIY including project planning and permitting, plumbing, basic electric, drywall, carpentry, tiling, painting and more. He also publishes noir fantasy thrillers, including The Carter Series, from Penguin imprint DAW Books.