Window Air Conditioning Chart (BTUs for Room Size)

illustration of air conditioner chart for BTUs and room size

The Spruce / Katie Kerpel

Central air conditioners incorporate two different coils in order to cool your home. This type of cooling system is used to cool the entire home, versus a window air conditioner that is used to cool a specific area or room of your home. The cooling compressor is set outside the home, separate from the fan unit used to blow the cool air throughout the home on the central air unit, unlike the window air conditioner that utilizes everything within one concealed unit.

Cooling Your Home Evenly

By using the existing heating/cooling ducts that encompass the entire home, the central air unit can cool the entire home evenly.

The coil that is placed outside of your home is called the condensing coil. It consists of a compressor, condensing coil condenser fan, a grill to protect persons from coming into contact with the fan blade, a case built around all of the components, controls, and two refrigerant lines that run into the home to the evaporator coil.

The refrigerant inside the compressor is pumped through the evaporator coil inside, which cools the air as the furnace fan blows air through the coil. The coil absorbs the heat from the air. Then the refrigerant flows back outside to the condenser coil and this is where the heat that was absorbed is released. At this point, the refrigerant (known as freon) is returned to a liquid form as it is cooled and the cycle of refrigerant flow continues.

Freon is a brand name. Many types of the chemicals used in it are being phased out. There are new gases being used today which is really beyond the scope of this article.

AC unit in a living room
Paolo De Santis / EyeEm / Getty Images

Getting the Size Right

Choosing the right sized air conditioner can be as easy as using a tape measure and a little mathematics. Simply measure the length and width of a room and figure the square footage. Let's say it is a 10 foot by 15-foot room. Multiply the two together to get 150 square foot room. Using the sizing chart to calculate the appropriate BTU rating needed to cool that area of the home, it's an easy selection choice from there. However, you are not done with the selection process yet. now you'll need to know what the window opening measurements are to allow the access of the window air conditioner into the appropriate space. Open the bottom window and measure the opening from the bottom of the window to the top of the window ledge. Now, measure the width from the inner-most part of the side window opening.

Written on the side of each box of window air conditioners, there's a chart that displays the opening size requirements for that particular window air conditioner. Check to see if indeed this unit will fit into the opening you have before purchasing the unit. Given that the window opening size may very well determine the size of the window air conditioner you'll be able to purchase, it's a good idea to do your homework first before purchasing anything.

Air conditioners cool your home and sizing the air conditioner to the room size is essential for proper efficiency and cooling capacity. Air conditioners are rated in BTUs and the BTU rating determines the cooling capacity in the square footage of the living area to be cooled. This air conditioning chart will help you choose the air conditioner to best cool your room.

Window Air Conditioning Chart

100 Sq. Ft. 5,000 BTU
200 Sq. Ft. 7,000 BTU
300 Sq. Ft. 9,000 BTU
400 Sq. Ft. 10,500 BTU
500 Sq. Ft. 11,500 BTU
800 Sq. Ft. 17,000 BTU
1,000 Sq. Ft. 21,000 BTU
Article Sources
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  1. Refrigerant Transition & Environmental Impacts. Environmental Protection Agency.