How To Buy A Window Air Conditioner

by Donald Grummett


Once again the summer heat is here and the rush is on to buy a new window air conditioner. And once again we have received many questions about what size of air conditioner should you purchase. The following are some suggestions.

If you take nothing else from this article, remember one simple rule, ‘When buying a window air conditioner Bigger is not always better’.

In fact, the air conditioner you purchase should be based upon the size of the room you wish to cool. If its cooling capacity is too high this can result in poor cooling, low moisture removal, short cycling of the compressor, and unnecessary electrical consumption.

The window air conditioners used in most homes vary in ratings between 4,000 BTU’s and 12,000 BTU’s.

The size of air conditioner required is based upon the square footage of the room to be cooled. Before purchasing, measure the length and width of the room. Multiply the measurements together to determine total square footage. Then use a BTU chart (often called a sizing chart) to approximate what BTU rating of air conditioner is required.

Some sizing charts go into great detail about things such as: type of house, type of windows, angle of sun, direction of windows, size of roof overhang, etc. These charts will give you a very accurate estimate of what size of air conditioner you require. But they are used primarily for calculating what size of central air conditioning system you might require. We only want to cool one room, not the whole house. Therefore manufacturers of window air conditioners use a more simplified sizing chart. The following is an example.

If room is 100 to 250 sq ft an air conditioner 5000 to 6000 BTU is suggested.

If room is 250 to 400 sq ft an air conditioner 6000 to 8000 BTU is suggested.

If room is 400 to 550 sq ft an air conditioner 8000 to 11000 BTU is suggested.

If room is 550 to 850 sq ft an air conditioner 11000 to 15000 BTU is suggested.

Don’t buy the largest capacity air conditioner you can afford. Even if the larger one is a better price. Don’t be tempted to oversize the one you need. Many consumers have done this and later regretted their decision.

The problem with an oversized unit is it will cool the room too quickly. This makes it cycle off too soon, resulting in very little moisture being removed from the room. Without moisture removal the overall cooling effect produced by the air conditioner is drastically reduced.

Therefore, if you have just bought a new a window air conditioner and it doesn’t seem to be cooling, then sit and watch it operate. If it cycles off and on rather quickly, seems to pump out lots of cold air, and yet does a poor job of cooling, suspect it of being oversized.

(This article is a shortened version of the original article, ‘What Size window Air Conditioner do you Need’. Copyright © 2005)

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