Correct Size Air Conditioning UnitCorrect Size Air Conditioning Unit

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September 2, 2014


Select the Right Size AC Unit

When you are purchasing a new air conditioner (A/C) for your home, it is important for you to select the right size air conditioning unit. You may be under the impression that bigger is better when it comes to purchasing an A/C unit, but the reality is an oversized A/C unit will cause problems in your home just as an undersized A/C unit would cause. It is best to take the time to calculate and figure out the best size A/C unit to purchase. With a simple math formula, you can have your answer and keep your home at the right temperature and the right humidity level.

The A/C Unit Size Should be Based on Size of Your Home

When it is time to purchase an air conditioning unit, you will have a variety of options in regard to size. It is important for you to look for an A/C unit which will accommodate the square footage of your home. The following is a list of square feet versus the needed BTU (British thermal unit) capacity:

  • 100-150 square feet – 5,000 BTUs
  • 300-350 square feet – 8,000 BTUs
  • 550-700 square feet – 14,000 BTUs
  • 700-1,000 square feet – 18,000 BTUs
  • 2,000-2,500 square feet – 34,000 BTUs
You will need to purchase the size of air conditioner that will fit the square footage and BTUs of your home.

How to Calculate Square Footage and BTUs

Calculating the size of the air conditioner needed for your home will mean using a formula that combines the square footage of your home and the needed BTU capacity. There are two different formulas that can be used to make these calculations:

  • For a room that is either square or rectangular, multiply the length of the area by the width
  • For a room that is triangular in shape, take the length of the area and multiply it by the width. Then divide by two.
  • Once you have made either of these calculations, use the chart above and find the square footage of your home which will correspond with the correct BTUs needed for the A/C unit.
Why the Correct Size is Important

Having the right-sized air conditioner is important for not only having the right temperature in a room, but also the correct humidity. Your air conditioner will take humidity and heat out of the room, but when a room has an air conditioner that is too large for the square footage; it will take out heat too quickly and will not remove the humidity as it should. When this happens, you will end up with a room that has too much humidity which could lead to other issues. So an air conditioner that is too small will not be effective, but one that is too large can cause other problems in your home.

In addition to humidity, efficiency is a major concern so purchasing a large air conditioner to serve a small home wastes money and energy. A small unit, on the other hand, will have to work extra hard to cool a large house and will wear out quickly.

Reference: Energy Star

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