Choosing the right window air conditioner starts with one number: BTU. As a rule of thumb, allow about 20 BTU per square foot of living space.
Start with square footage
Measure the length and width of your room and multiply them. A 12 by 25 foot room is 300 square feet, which calls for roughly 6,000 BTU.
Adjust for conditions
- Sunny rooms: add about 10 percent.
- Heavily shaded rooms: subtract about 10 percent.
- Kitchens: add 4,000 BTU.
- More than two people regularly in the room: add 600 BTU per person.
Do not oversize
A unit that is too powerful cools the air quickly but cycles off before it removes humidity, leaving the room cold and clammy. Right sizing keeps you comfortable and efficient.
