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Window Is Too Wide For Air Conditioner? (6 Solutions)

Window Is Too Wide For Air Conditioner? (6 Solutions)

If you are like most other people in affordable apartments, you have a window unit for your air conditioning needs. A typical window air conditioner is going to be petite, often meant for 24-inch windows.

Are you worried that you won’t be able to fit your AC unit into your window area without it falling off? Here’s the scoop on the solutions that you have available to you.

How can you work with a window that’s too wide for your air conditioner unit?

Window AC units are fickle things, but they’re not impossible to work with. If your window frame is wider than the unit, you have a couple of installation options to consider.

1. Use plywood

If you need to affix your AC unit to the window, use plywood to shorten the distance from the window’s sides. You can then affix the plywood to the window using duct tape to reduce leakage of cold air to the outside area.

It’s a cheap solution that works in a pinch. The downside of this is that you may need to insulate the area with weather stripping and spray foam sealant, but that’s true about most solutions here.

PRO TIP – Use the plywood as a way to balance the unit against the window or to add extra holes along wooden areas near your window frame if you need to steady it. Drilling holes in your unit to hold the plywood can void the AC unit’s warranty.

Use plywood


2. Use cardboard

Cardboard works the same way as plywood. You can stack and tape cardboard to the sides of your window until you are able to get your unit right where it needs to be. With that said, this isn’t good to use if you have a major gap because your unit can fall off your windowsill.

Cardboard is often better used as a form of insulation, or something of a soft cushion for your portable AC unit. Since cardboard can get moldy when wet, this is definitely best used as indoor insulation or a temporary fix at best.

3. Use an AC unit window extension

Window extensions are “wings” designed to make it easier for your unit to fit into your window. The premade ones found in your local hardware store are often insulated and designed to make air conditioner installations easier for you.

These window extensions tend to work best for units that are only 6 to 18 inches smaller than the window they’re supposed to be added to. If you notice leaks, use duct tape and foil to fill in any air gaps.

It’s worth noting that this is the most aesthetically pleasing solution here. If you want your living room to look good while you keep your entire home cool, then this might be the best choice for you.

PRO TIP – Many air conditioner companies make model-specific extensions for their units. If you can find one that matches your model, that’s your best bet.

4. Use foam sealant

If you just have little gaps between your double-hung window and the AC unit, don’t panic. You can actually use spray foam sealant to insulate and hold your unit in place. Like other options on this list, this is a smart way to prevent air leaks for years to come.

The big issue many people have with it is that it tends to look ugly and it can also stick to your walls. If you have a “misfire” while adding this sealant, getting this stuff off your window or wall can be a nightmare.

5. Change windows

Yep! If you have different sized windows, you can always beat the summer’s heat by switching the window used for your AC unit. It’s an obvious but highly efficient option.

Obviously, this is not an option everyone has, but if you have a high-powered unit, even placing it in a different room won’t make that much of a difference.

If all else fails, consider getting a larger AC unit

If you have a large home or just need to cool down large rooms, you might be using an AC unit that doesn’t actually work well. This could mean that all the work your doing might end up being for nothing at all.

Most AC units will require a minimum to maximum window size of 22 to 36 inches. This is good, considering that the standard vertical window size currently rests at 24 inches in width. Larger and more powerful units may work with windows as wide as 45 inches!

Now would be a good time to check the BTUs on your unit and see how many square feet your air conditioner should be good for. If it’s not big enough to cool down your large rooms or your home, it may be better to seek out higher BTU models that will also fit your window.

It’s best not to make the same mistake twice. So, before you hit the store, make sure to measure your window length.

If you just bought a new air conditioner and it was too small, take it back to the hardware store and exchange it for a bigger one. It may be easier than trying to finagle it into working with your window.


Overall, most windows can be refitted to work with a smaller AC unit. The only thing you have to do is find a way to reduce air gaps. This prevents cool air from leaking outside and keeps bugs from crawling in.

No matter how you look at it, you have a decent number of choices that you can use to re-fit your unit and avoid the hot, sizzling July sun. It’s only up to you to decide which option suits you, your home, and your heating needs best.