How to Properly Size a Window Air Conditioner
Don't buy a more powerful unit than you need
Size matters when you’re buying a window AC.
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.
What Size Air Conditioner Do You Need?
Bedroom or home
sq. ft. 100-300
Primary bedroom or
sq. ft. 250-400
Living room, family room,
or open plan
sq. ft. 350-650
The Rules for Keeping Cool
Window air conditioners typically have a cooling capacity ranging from 5,000 to 12,500 British thermal units (Btu/hr.). As a rule of thumb, an air conditioner needs 20 Btu for each square foot of living space.
But 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 ACs for Small Rooms
For a small bedroom, home office, or guest room, ranging from 100 to 300 square feet, look for an air conditioner with a capacity of 5,000 to 6,500 Btu. You’ll want one with good scores for comfort and noise. Here are three top-rated models.
Best ACs for Midsized Rooms
To cool a bigger or busier room ranging from 250 to 400 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 ACs for Large Rooms
For a living room or family room (350 to 650 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 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 higher the EER, the lower your operating costs. All the models in CR’s air conditioner ratings have an EER of 10 or above.
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 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 forget to do it before you leave the house.
Maintaining Your Air Conditioner
We rely on our window air conditioners to keep us cool when temperatures climb. On the “Consumer 101” TV show, Consumer Reports expert John Galeotafiore explains to host Jack Rico how to maintain a window AC unit to ensure cool, clean air throughout summer.