How to Determine the BTUs Your Air Conditioner Needs for Proper Cooling

Choosing the right air-conditioner capacity is important.

On a hot summer day, it might seem that the more power your room air conditioner has, the better. But the opposite is true. The number of BTUs (British Thermal Units) a window-mounted air conditioner produces per hour is an important guideline when figuring the right size to buy. According to the California Energy Commission, an air conditioner that has too much power for the size of the room will be less efficient than one that's properly sized. And a too-small unit will run constantly without cooling the room effectively. Follow the commission's tips for choosing an air conditioner that's just right.

Things You'll Need

• Tape measure

Instructions

1. Measure the length and width of the room you'll be cooling with the air conditioner. Multiply the numbers together to determine the room's square footage.

2. Choose an air-conditioning unit based on your room's square footage. For example, a room of 100 to 150 square feet needs a unit with just 5,000 BTUs, while a room of 450 to 550 square feet needs an air-conditioner that produces 12,000 BTUs.

3. Add 10 percent to the BTU figure if your room has a sunny eastern or western exposure. Deduct 10 percent if the room gets a lot of shade, thus staying cooler.

4. Increase the number of BTUs if more than two people will be in the room on a regular basis. Add 600 BTUs for each person over two.

5. Boost the capacity of your air conditioner by 4,000 BTUs if it will be installed in the kitchen. Your oven, refrigerator and other kitchen appliances can make the room warmer.

Tips & Warnings

• Look for an air conditioner with the Energy Star rating, given by the federal government to high-efficiency appliances.

References

• California Energy Commission: Window Air Conditioners