How to Size a Window Air Conditioning Unit

By | March 22, 2020

How to Size a Window Air Conditioning Unit
Getting the right size window air conditioner for a room is necessary otherwise it may not cool the room completely.

  • If a unit is too small it will not cool the room and a unit will run constantly.
  • If a unit is too big for a room it will quickly cool a room and shut off which can run up an electrical bill.

Air conditioners use the most power when they startnup which makes an oversized unit use more electricity with it constantly starting and stopping.

Having the correct window unit for a room will make it start and run for the right amount of time cooling a room the best possible way.

So What Is the Right Size A/C Window Unit?
All air conditioners use what is called BTU (British Thermal Units) to measure the amount of cooling power they have.

The square feet a room has is all the information needed to get the right window unit.

To get the square feet of a room simply multiply the width by the length.
How to Size a Window Air Conditioning Unit pic 2
For example, a room 10 feet wide by 15 feet long would be 150 square feet.

To get the BTUs needed device the number by .05 which will give the size needed for the room.

For example, the 10 X 15 = 150 square feet.

150 / .05 = 3,000 BTUs
How to Size a Window Air Conditioning Unit pic 3
One thing to keep in mind while sizing a unit is other factors such as how well insulated the room is, are doors constantly being opened, how hot does the outside temperature get, and so on.

Most will find that a slightly bigger unit is needed.

Window Air Conditioner Sizing Chart

100 to 150 Sq Ft5,000 BTUs
150 to 250 Sq Ft 6,000 BTUs
250 to 300 Sq Ft 7,000 BTUs
300 to 350 Sq Ft8,000 BTUs
350 to 400 Sq Ft 9,000 BTUs
400 to 450 Sq Ft 10,000 BTUs
450 to 550 Sq Ft 12,000 BTUs
550 to 700 Sq Ft 14,000 BTUs
700 to 1,000 Sq Ft 18,000 BTUs
1,000 to 1,200 Sq Ft 21,000 BTUs

Getting the right size window air conditioner for a room can be critical to get the best cooling for the lowest running cost.

While on paper simple math will give a rough idea in the real world other factors need to be taken into consideration.

For example, a kitchen will need a bigger unit to help dissipate heat, or a room that is poorly insulated.

Often it can take a bit of trail and error for most with the above a generalization.

When buying a unit keep in mind the efficiency rating and other factors such as how quiet a unit is also plays a role.



2 thoughts on “How to Size a Window Air Conditioning Unit

  1. Darlene Biggs

    I need instructions on how to get the right size and condition of for my window for to fit in my window not the square footage to cool walk the world


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