What Is A Casement Air Conditioner?

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Updated May 15, 2023

The best air conditioners come in all shapes, sizes, and specs. Some worry that their specific window frames may not fit an air conditioning unit. This is where casement ACs come in. Casement units (also known as vertical air conditioners) perform the same as typical window units. Essentially, casement units are explicitly shaped to fit into a casement window. Therefore, when it comes down to understanding how to use an air conditioner, regular or casement, there’s no difference.


  • Casement air conditioners are a type of window air conditioner shaped to support the vertical design of casement windows.
  • Casement units require a special window kit for safe installation.
  • Casement windows typically require a unit with a minimum height of 15-20 inches.

An important matter for anyone interested in purchasing a new AC unit is understanding what BTU means for an air conditioner and how many are needed to cool a space adequately. The features of the unit should be considered, such as the sleep mode and programmable timer, to ensure maximum energy efficiency.

Insider Tip

Some casement air conditioners come with window mounting kits that include the plastic/styrofoam insert to hold the unit in place.

Why Use Casement ACs?

Many modern homes have casement windows for their unique style and energy-efficient design. The only problem is that regular window units won’t fit, as casement windows are usually vertically shaped, narrow, and held in places by hinges that open outwards via a crank, making typical AC units too wide.

For some great additional resources on all different AC types, where we have a range of helpful resources, such as our explainer about what a mechanical air conditioner is.

What to Know About Casement AC Units

While casement AC units provide a simple solution to a tricky problem, there are some things homeowners must be aware of before purchase and installation.


Never install a casement air conditioner without fitting it properly into the window sill. The unit can fall out and cause severe damage to the unit or anyone standing underneath it.

A casement window AC unit is taller than it is wide. Most casement ACs are close to 20 inches tall and 10 inches wide; this way, it fits in the slimmer window frame.

Because of this, casement AC installation requires more hands-on work than regular window units. To begin the installation, remove the swinging window panel. Then, cut an insert made of Plexiglass, plastic sheeting, or similar material, and then cut another hole for the AC unit. Finally, install the mount, and insert the casement AC unit.

STAT: Most casement window units are at least 15 inches in height. (source)

Although the installation is different, remember to perform all the general upkeep you would with an ordinary window air conditioner. This includes changing the air filter frequently, properly storing it for winter, and keeping it free of dirt and debris buildup. And a vital upkeep measure is knowing what size air conditioner filter you need.

What Is a Casement Air Conditioner FAQs

How much do casement air conditioners cost?

Casement AC units tend to cost anywhere from $400-$600.

Can you rotate a normal window AC unit and use it in a casement window?

Never use a standard AC unit on its side. The window unit’s freon will leak out, which is hazardous.

Are casement AC units energy efficient?

As with all window units, many come with energy saver modes and are highly rated by organizations like Energy Star.
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