Know how powerful an air conditioner to buy
 
The first thing you're going to come across when you go a/c shopping is the term "Btus." Here's what it means: every air conditioner has a cooling capacity number that ranges from 5,000 to 18,000 Btus. The higher the Btu value, the stronger the air conditioner is. (For the people out there interested in such things, "Btu" stands for "British thermal units.")

There are two methods to figuring out how many Btus you need:

  • Find the square footage of the room (multiply its length and width). Then check out to see where you fall.
  • Find the square footage of the room, and multiply the answer by 35. That'll get you in the right ballpark.

Here's an example: Let's say your apartment is 12' x 15'. So that's 180 square feet. Using method (1), you know that you should be looking for an air conditioner in the low 6,000 Btus. Using method (2), you are recommended to get an air conditioner with about 6,300 Btus (180 X 35).

In addition, you should follow the following guidelines for proper selection:

  1. If the room is shaded, reduce the Btus by 10%.

  2. If the room is very sunny, increase the Btus by 10%.

  3. If you plan on placing the air conditioning unit in your kitchen, add 4,000 Btus.
  4. If more than two people will regularly be in the room (e.g., an office), add 600 Btus per person.