How to Figure the Room Size for an Air Conditioner

An air conditioner's capacity to cool is measured in British thermal units (BTU). It is crucial to use an appropriate air conditioner for your room size to get the best results. If the air conditioner is too small, it won't cool your room and will be overworked, which will cause it to wear out faster. If it is too large, the air conditioner will shut off once it has cooled the room but before it has lowered the humidity, and it will cost more to purchase.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Calculator

1. Determine the capacity of your room air conditioner. It will be listed on the Energy Star label as well as in your owner's manual.

2. Subtract 4,000 BTUs from the air conditioner's capacity if you are going to be using the air conditioner in a room used as a kitchen.

3. Subtract 600 BTU from the air conditioner capacity for each person beyond the second who will be living in the room. For example, if there are four people living in the room, subtract 1,200 BTUs from the capacity.

4. Multiply the capacity by 0.9 if the room is very sunny or by 1.1 if the room receives minimal sunlight.

5. Use a sizing chart to figure the room size for an air conditioner. These are available online. (See Resources.) For example, if your adjusted capacity is 9,000 BTUs, you can cool a room between 350 and 400 square feet.

References

• Properly Sized Room AC
• Room Air Conditioners: Energy Star