Can a window AC be mounted vertically?

A window air conditioning unit can only be mounted vertically if it is a vertical window AC designed for narrower sliding windows with smaller width dimensions.


Having an air conditioner installed in your home means preparing it for the unit and figuring out if the unit is suitable for where it needs to go. This is the case when it comes to window air conditioner requirements.

Windows come in different shapes and sizes and either open with up-and-down motions or by sliding from left to right. In the case of a sliding window, a window unit needs to be installed vertically as sliding windows are narrower, so a regular window unit will not work.

Are all window air conditioners the same size?

Typically, people are used to seeing a window air conditioner mounted horizontally in a horizontal square-shaped window. But some windows are rectangular-shaped with a smaller width. In this case, a regular window air conditioner will not be the best option as it will not fit in a narrower window.

So, can a window air conditioner be fitted into the window vertically? Fortunately, there are different kinds of window units available to solve the issue of a window being too narrow to fit a standard window air conditioner.

Can a window AC be mounted vertically?

A window air conditioner can be mounted vertically as long as it is a vertical casement window air conditioner.

No other window air conditioner can be installed in a window vertically besides a casement AC unit, because this unit is intended to be installed into the vertical space of narrow window openings.

Vertical or casement window units have smaller widths than regular window air conditioners, which makes it easy for them to fit in the narrower windows.

Vertical windows usually slide from left to right to open and close, and this is why vertical window air conditioners are best suited for these windows.

Some people might try to install a regular window AC unit in the place of a vertical window AC unit, but this is not advisable as it can cause damage.

The difference between installing a vertical window AC and a standard window AC

Both standard and vertical window units are designed to fit into a window opening and rest on the sill with most of the unit outside.

The difference, however, is that vertical units have metal or plastic edges on the sides, or a piece of plastic that fits over the unit to hold it against the insides of the window opening, whereas a standard window unit has an edge on top of it to rest against the inside of the sash of the window it is situated in.

Considering the cooling size of vertical window AC units

If you have decided to get a vertical window air conditioner, you need to consider the fact that these units only come in two cooling capacity sizes:

  • 8000 BTU, which is good for cooling rooms of about 300 to 350 square feet,
  • 10 000 BTU, which is good for cooling rooms of 400 to 450 square feet.

These are the only size options of cooling capacities, so consider if this is worth it.

Advantages and disadvantages of a vertical AC unit

A vertical window unit has its advantages and disadvantages. Below we take a closer look at these.

Vertical AC unit advantages

Vertical AC unit disadvantages

Customisable Large and heavy
Best for temporary living conditions Unappealing to the eye
No complicated electrical and hose adjustments Your window is technically slightly open, and not fully closed
Drains outside the window The room is vulnerable to air leaks and unwanted air entering the room

Final thoughts

Investing in a window air conditioner means ensuring that the window you want to install it in is equipped to hold this AC unit.

For vertical and narrower units, you need a unit that can fit in the narrow window space seamlessly. This is when a window air conditioner can be mounted into a window vertically.

There are vertical window units known as sliding or casement window air conditioners specifically designed for narrower windows with a smaller width. These units are the best for narrow, vertical, and sliding room windows.

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