How to Size Room Wall Air Conditioner

The size of a room wall air conditioner depends on the size of the room, how the room is used and how the room is built. The capacity of a wall air conditioner is measured in British thermal units, or BTUs. When you purchase a unit that is too small, it will not last as long because it will be overworked. If you purchase a unit that is too large, it will waste energy because it will cycle on and off.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Measuring tape

1. Measure the size of the room the air conditioner will cool.

2. Use a chart that you can find online, such as one from Lowes or the Department of Energy (See Resources.) to estimate the size of the air conditioner you will need. For example, a 500-square foot room would need an AC unit with a capacity of about 12,000 BTUs.

3. Determine the amount of sunlight the room will get. If it is significant, add 10 percent to the capacity found in step 2. If the room is exposed to very little natural light, subtract 10 percent.

4. Determine the use of the room. If it will be used as a kitchen, add 4,000 BTUs. If it will have more than two people living in it, add 600 BTUs for each additional person.

References

• Properly Sized Room AC
• Lowes AC Guide

Resources

• Department of Energy
• Lowes