Home Central Air Conditioner Sizes

BTUs and Tons

• The size of your central air conditioner is stated in BTUs or tons. A BTU, or British thermal unit, is the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit. The air conditioner may be referred to in this manner or in tons. One ton is the same as 12,000 BTUs. A ton is the amount of energy needed to melt a ton of ice in one day. Most home central air conditioners are between 3 and 6 tons, or 36,000 and 72,000 BTUs.

Too Big

• You may be thinking that you should simply buy the biggest central unit you can afford and it will do a good job. This is not true. If you choose a unit that is too large for the space you need to cool, it can result in several negative effects. There will be unnecessary wear and tear on the unit as it cycles on and off too often, leading to premature failure. The system will not stay on long enough and will therefore not remove adequate humidity from the air to make the room as comfortable as it should be. Also, the temperature in the house is likely to be inconsistent.

Too Small

• Going the other way and trying to save money by buying the smallest system possible can be equally bad. If you buy a central air conditioner that is too small for your space, you will find that it raises your energy bills because the system has to run too often as it tries keep up with demand. This burns a lot of extra energy. The small system also will not be able to control the heat as quickly, if at all. This will result in a less-comfortable home, which defeats the whole purpose of having air conditioning.

Factors to Consider

• You cannot judge the size of a central unit simply by figuring square footage of the area to be cooled. This may be a good place to start, but there are many other factors that have a drastic effect on the needs for cooling capacity. Have the installer come to your home for an evaluation to determine your needs. The professional will check out insulation levels, the number of windows and which way they face, wall surface, height of ceilings, amount of shade from trees and other factors to determine your specific needs.