How to Calculate What Size Central Air Conditioning You Need

Each home is different, so it is really essential to find the correct air conditioner. The design of the central air conditioner relies on various variables, aside from the size of your room. Such variables include the roof size, ceiling height, number of windows, type of insulation, wall heat transfer, etc. Typically, the size specified in the manufacturer’s recommendations may not take these variables into consideration and may therefore be inaccurate.

What Size Central Air Conditioner Do I Need?

When we talk about air conditioner size, we do not mean your unit’s physical size. In order to evaluate how much heat it can remove in an hour; the size of AC is expressed in tons. A typical AC unit, for example, is one ton and it cools 12000 BTU/hour. BTU is a measure of heat. If you consider how many BTUs are needed to cool a 100-300 square feet home office or a bedroom, it is approximately around 5000-6000 BTUs.

Why Size Matters

A correctly sized air conditioner is essential to make sure your home stays cooler longer by running a proper full cycle. If the air conditioner is not big enough, it will have to work constantly to keep your home cool throughout the summer. It would dramatically increase the electricity bills. On the other hand, if the air conditioner is very large, the room can cool too quickly, forcing it to run for very short cycles. In these situations, the device is unable to adequately extract the moisture from the air that may cause mold and fungus problems. In these situations, too much on-off switching will wear out the air conditioner faster.

How to Measure What Size Air Conditioner You Need

Calculating the size air conditioner needed for a room is fairly simple. First multiply the width of the room by its length, then multiply it with 25 BTU to get sufficient cooling, under different weather conditions, for the room. (W x L x 25) So, if the room is 12 feet wide and 15 feet long, it equals 180 square feet. Now multiply 180 by 25 BTU per square foot and you get 4500 BTU. This then is the minimum cooling capacity of air conditioner you should buy.

If you are considering an air conditioner for your Lynnwood or Seattle area home or business, please give us at Kings Heating a call. We would appreciate an opportunity to be of assistance to you.


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