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How to Properly Size Portable Room Air Conditioners

Posted by Brenda Roy on Jun 13, 2017 5:03:21 PM

How many BTU's Do I Need for My Room?

This chart may help you determine what size portable air conditioner shop for. A word of caution: don't buy an air conditioner that's too large. An oversized air conditioner is actually less effective - and can waste valuable energy at the same time. Because portable air conditioners remove both heat and humidity from the air, an oversized unit will cool the room quickly, but only remove some of the humidity. This will leave your room with a damp, clammy feeling. A properly sized unit will effectively remove humidity as it cools.

To figure out which size Air Conditioner is best for your cooling needs:

1. Determine the square footage of the area to be cooled using the following formulas:

  • For square and rectangular rooms, multiply the length of the area by its width - L x W
  • For a triangular area, multiply the length of the area by the width and divide by 2 - L x W / 2

2. Using the square footage and the chart below, determine the correct cooling capacity. Cooling capacity is measured in British thermal units (BTUs) per hour.

Area To Be Cooled (square feet)  Capacity Needed (BTU's per Hour) 
100 to 150 5,000
150 to 250 6,000
250 to 300 7,000
300 to 350 8,000
350 to 400 9,000
400 to 450 10,000
450 to 550 12,000
500 to 700 14,000
700 to 1,000 18,000

3. Make any adjustments for the following circumstances:

  • If the room is heavily shaded, reduce capacity by 10 percent.
  • If the room is very sunny, increase capacity by 10 percent.
  • If more than two people regularly occupy the room, add 600 BTUs for each additional person.
  • If the unit is used in a kitchen, increase capacity by 4,000 BTUs.
  • Consider where you install the unit. If you are mounting an air conditioner near the corner of a room, look for a unit that can send the airflow in the right direction.

Topics: Portable Air Conditioners

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