How to Properly Size a Window Air Conditioner
Picking the best window ACs for small, midsized, and large rooms ensures you don’t spend more than you need to
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Size matters when you’re buying a window air conditioner. An air conditioner that’s too small will struggle to keep a room at a comfortable temperature. A model that’s too big will cool a room too quickly without removing enough humidity from the air, leaving you cold and clammy.
Choose just right and you’ll feel just right—and save money, too. Consumer Reports tests window air conditioners in rooms that are the same size as the ones they’re intended to cool, helping you select the best model for your needs.
What Size Air Conditioner Do You Need?
Bedroom or home
office
sq. ft. 100 to 250
btu 5,000-6,500
Primary bedroom or
playroom
sq. ft. 250 to 350
btu 7,000-8,500
Living room, family room,
or open plan
sq. ft. 350 to 550
btu 9,800-12,500
The Rules for Keeping Cool
While a window air conditioner’s Btu rating is a great starting point, other considerations, such as the ceiling height and the size of your windows and doorways, might call for more cooling power.
To measure your room, multiply the length by the width. Add together the size of rooms that aren’t separated by doors, because the air conditioner will need to cool both spaces. Energy Star recommends that you make adjustments for the following circumstances.
• If the room is heavily shaded, reduce capacity by 10 percent.
• If the room is very sunny, increase capacity by 10 percent.
• If more than two people regularly occupy the room, add 600 Btu for each additional person.
• If the unit is used in a kitchen, increase capacity by 4,000 Btu.
Best Window ACs for Small Rooms
For a small bedroom, home office, or guest room, ranging from 100 to 250 square feet, look for an air conditioner with a capacity of 5,000 to 6,500 Btu. You’ll also want one with strong scores for comfort and noise. Below are three top-rated models from our tests. Check out our air conditioner buying guide to learn more about how we test window ACs and key features to consider when you go shopping. CR members can dive into our full window AC ratings.
Best Window ACs for Midsized Rooms
To cool a bigger or busier room ranging from 250 to 350 square feet, 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 Window ACs for Large Rooms
For a living room or family room of 350 to 550 square feet, 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 solid choices.
Money-Saving Window AC Tips
Tougher federal energy standards for window air conditioners make newer models cheaper to run. Look for a unit with an Energy Star label and an energy-efficiency ratio (EER) of 10 or above. “The EER is the ratio of the cooling capacity (in British thermal units (Btu) per hour) to the power input (in watts). The higher the EER rating, the more efficient the air conditioner,” writes the U.S. Department of Energy. In other words, the higher the EER, the lower your operating costs. All the models in CR’s air conditioner ratings have an EER of 10 or higher.
Keeping your AC in peak condition can also help you save. Look for a model with a filter that’s easy to remove for regular cleaning. A dirty filter causes an air conditioner to work harder.
Many air conditioners also have a timer that you can set to cool a room before you get home. And some have an app for your smartphone that you can use in case you forgot to set the timer before you left the house.
Maintaining Your Window Air Conditioner
We rely on our window air conditioners to keep us cool when temperatures climb. Consumer Reports expert John Galeotafiore explains how to maintain a window AC unit to ensure cool, clean air throughout summer.
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