Window Too Small For AC? AC Doesn’t Fit Window? (2 Viable Options)

In general, window AC units require wide windows. If you have a narrow window, you run into a problem because the air conditioner doesn’t fit the window. Not to worry, however; even if your window is too small for an air conditioner, you can use a special kind of vertical window AC unit, or, in extreme cases, exhaust a portable AC hose through that slim window.

Here’s the problem: Let’s say that you have a 20-inch window width (or even smaller). You want to install a window AC. Most 10,000 BTU or 12,000 BTU window AC units require a window that is at least 20 inches wide. Yes, you can opt for one of these smallest window AC units that require about 17-inch window width but those produce only 5,000 BTU or 6,000 BTU of cooling output. That’s usually not enough cooling output for a standard-sized room.

air conditioner doesnt fit window
Narrow 20 inches or less wide windows are usually too small for a standard window air conditioner.

Most conventional window AC units are horizontal; they are quite wide and low. That’s why these AC units don’t fit the window.

In this case, you have to opt for a so-called casement window air conditioner. Here’s what these AC units are:

Casement AC Units For Narrow Windows

While standard window AC units are horizontal, the casement window AC units are vertical. That simply means they are slim and tall.

These casement window AC units have:

  • A minimum window width requirement of only 15.5 inches.
  • Can produce up to 10,000 BTU of cooling output.

Even if your standard window air conditioner doesn’t fit the window, chances are that a casement window AC unit will fit in that narrow window.

Example: Let’s say you have a 16-inch, 17-inch, or 18-inch wide window. A standard window AC has a minimum required width of about 20 inches; thus it won’t fit in this window. On the other hand, however, a casement window AC unit has a minimum required width of 15.5 inches; that means it will fit into a narrow window and even have some extra room on the left and the right that you have to seal with the window AC seal kit.

casement window when standard window is too small for ac
Example of a casement window AC unit is a narrow 16-inch wide window.

The good thing about these narrow AC units is that they can still provide a lot of cooling power. Of course, for that, they need to include a powerful compressor, a bigger fan and a more powerful fan motor.

Casement window AC units are tall precisely for that reason. That extra space that we get by engineering a tall window AC is used to store the compressor, fan, and fan motor, capable of producing almost 1-ton of cooling output.

If you need some suggestions regarding these tall and narrow window AC units, you can check a list of the best casement window air conditioner here.

If your windows are extremely narrow (window with less than 15.5 inches), even casement window AC units won’t fit. In such a case, it is best to get a portable AC unit and put the exhaust hose out of that narrow window. Exhaust hoses have a diameter of about 5 or 6 inches; they can easily fit in pretty much any window, no matter how small.

All in all, if your windows are too small for a window air conditioner, you can:

  1. Choose a special casement window AC unit that is slimmer and will fit even a small window.
  2. For very narrow windows, opt for a portable air conditioner that is exhausted through that window.

Hopefully, with these two options, you can provide cooling to a room no matter how small a window you have.

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