Calculating Portable Cooling Requirements

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Calculating Portable Cooling Requirements

Portable air conditioners are sized according to BTUs, which stands for British Thermal Units. A BTU is a unit of energy that is commonly used in the power, steam generation, and heating and air conditioning industries. Generally speaking, a portable air conditioner’s BTU rating describes its power and cooling capacity. Naturally, the higher the BTUs, the stronger the portable AC. Portable air conditioners have cooling capacities that usually range from 12,000 BTUs to as high as 77,500 BTUs, and the size needed to cool a room will depend on the area being cooled.  Thus, an incorrectly sized portable AC with insufficient or excess BTUs will result in inefficient cooling.

Before you decide on your area’s BTU requirements, first compile the following information:

  • Calculate your room’s square footage by multiplying its length by its width.
  • What voltage is available – 115, 208/230 or 460
  • Type of ceiling – drop down plenum (you will need a place to exhaust heat)
  • Where can we drain condensate? Will you need tanks or a pump?
  • What kind of equipment is in the room, such as server racks, telephone switching equipment, power supply backups, any types of heat generating equipment and people.
  • Are there any windows in the room?

After these have been verified, it is then time to determine your BTU requirements. Simply look to the chart below:

Portable Air Conditioner Sizing Chart

Room Square Footage

Required BTUs

100 – 400


400 – 800


800 – 1200


1200 – 1600


1600 – 2000

65,000 – 76,500

For example, if your room measures 20 feet by 20 feet, your calculations will look like so:

20′ x 20′ = 400 square feet

400 square feet = at least 12,000 BTUs

As such, if your room measures 400 square feet, you will need a portable air conditioner that offers 12,000 BTUs of cooling. Note that the figures in the chart above are estimates based on average room conditions in a moderate climate.