Cooling Capacity of an Air Conditioner

How an Air Conditioner Cools

• The air conditioner cools the room by cooling the air that passes through the unit over the cooling coils. The air gets colder and the humidity is removed before the air is sent back into the building or room.

Size

• The size of the air conditioner you need to cool a building or specific room depends on the size of the space. The area is determined by measuring the length by the width. For instance, if the area is 350 to 400 square feet, you need an air conditioner with 9,000 BTUs. For a building that is 2,000 to 2,500 square feet, you would need a unit with 34,000 BTUs.

Size Adjustments

• Before you select an air conditioner strictly on the size of the room or building, you need to make adjustments for shade, sun and occupancy. If the room or building will have more than two people occupying it, add 600 BTUs for each person over two. If the room or building has a heavily shaded side, subtract 10 percent from the BTUs.

  For instance, if you need a 9,000 BTU unit, but have an area of the room or building that has more shade than sun, subtract 10 percent from 9,000, which lowers the BTUs needed to 8,100. Add 10 percent if the building or a room has a lot of sun. If the air conditioner will cool a kitchen, add 4,000 BTU.

Oversizing or Undersizing

• If you use a unit that has a lower cooling capacity than what you need, the air conditioner will continue to run and waste electricity, but won't cool the room or building effectively. Units that have more BTUs than what you need in the room or building will short cycle and turn off and on more, but won't be as effective at removing the humidity.