Is It Time to Get a New Window Air Conditioner?

• When to Replace Your Old Air Conditioner
• Best Air Conditioners for a Small Room, Midsized Room, and a Large Room 
• How CR Tests Window Air Conditioners

If your window air conditioner is on the fritz—for example, it’s struggling to produce cooler air or it’s making noises—there are a few steps you should take to evaluate it before you retire it for good. Of course, if your warranty covers any of the issues you discover, you may be able to repair the unit rather than ditching it—warranties usually last between one and five years.

• First, inspect the seal around the unit to make sure warm air isn’t getting into the room or cold air isn’t escaping. If leaks are present, reseal the unit with weather stripping.
• Next, remove the filter (usually located just behind the grill) and clean it with warm, soapy water; over time it can get clogged with dirt and dust, which reduces airflow through the unit, diminishing its efficiency and ability to clean the air. 
• While the filter dries, check the now-visible evaporator coils. If they’re covered in dust, clean them with your vacuum’s upholstery brush, taking care not to bend the fragile fins.

“If the air coming from the unit is warm, you may have a problem with the compressor or the level of refrigerant, and should replace your window air conditioner if it’s out of warranty,” says Chris Regan, who manages CR’s air conditioner testing.

For a small bedroom, home office, or guest room, look for an air conditioner with a capacity of 5,000 to 6,500 Btu, which are made to cool rooms ranging in size from 100 to 250 square feet. You’ll want one with good scores for comfort and noise. Here is our top choice from our top-rated models for small rooms.

To cool a bigger or busier room—from 250 to 350 square feet—you’ll want to step up to a midsized air conditioner rated 7,000 to 8,500 Btu. If it’s for a bedroom, heed our noise scores. The best performing models for midsized rooms include features like a remote control, built-in timer, and dirty filter indicator—including this Frigidaire below.

For a living room, family room, or other space around 350 to 550 square feet, you’ll want a large air conditioner, 9,800 to 12,500 Btu, especially if you have an open floor plan. And while the top tier models for large rooms earn impressive scores for reliability, comfort, and ease of use, this is our best pick.

If it’s time to buy a new window air conditioner, Consumer Reports can help you hone your search. We tested more than 40 window air conditioners in our labs.

After installing a unit in a double-hung window in our climate-controlled testing chamber, we crank up the air temperature to 90° F, then measure how long it takes the AC to cool the room by 10° F. The best units hit the mark in less than 15 minutes. We also gauge how accurately the AC reaches its set temperature, whether it can recover from a simulated brownout, the intuitiveness of the controls, and how loud each unit is when running on low and high.