Top 7 Vertical Window AC for Sliding/Casement Window in 2024

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The best casement window air conditioner models are quality ACs that fit casement and sliding windows. We have a great list of them below for you to review and choose one today, if you’d like to.

Plus, you’ll find a very handy window kit that allows you to use a portable air conditioner with a casement window.

Next is our Quick Picks list of the best casement window air conditioners for this year. There are bullet points with the essential specifications.

After that are Full Reviews of the best slim vertical window air conditioner models followed by more content to assist you in finding the right AC for your needs.

Buying tip: The minimum window opening width for these casement window air conditioners is 15 ½”. Knowing this allows you to measure your window and know the AC will fit before you buy!

Top 7 Casement or Vertical Window Air Conditioners – Quick Picks

Here are overviews of each. The Full Reviews are found below for those who want to do further research before making a choice.


#1 Koldfront CAC8000W

  • 8,000 BTUs, 250-350 sq. ft. 
  • 20.8 X 14.5 X 23.5 Inches
  • Energy star, Remote

#2 Frigidaire FFRS0822S1

  • 8,000 BTUs, 250-350 sq. ft. 
  • 23.5 X 14.2 X 20.2 Inches
  • Remote, 24H timer

#3 PerfectAire 3PASC10000

  • 10,000 BTUs, 350-450 sq. ft. 
  • 23.5 x 14.5 x 20.5 inches
  • Remote, 5 modes

#4 Frigidaire FFRS1022R1

  • 10,000 BTUs, 350-450 sq. ft. 
  • 23.5 x 14.5 x 20.2 inches
  • Remote, 24H Timer

#5 Arctic King 10,000 BTU

  • 10,000 BTUs, 350-450 Sq. Ft. 
  • 23.5 X 14.6 X 20.9 inches
  • Remote, 5 Modes

#6 Keystone 10,000 BTU

  • 10,000 BTU, 350-450 sq. ft.
  • 23.5 x 20.87 x 14.57 inches
  • Popular sliding window AC

#7 Koldfront CAC10000W

  • 10,000 BTU, 350-450 sq. ft.
  • 23.5 x 14.5 x 20.87 inches
  • Remote plus Dehumidifier

What is a Casement Window AC? Vertical AC?

See the picture below. But first, here are our terminology tips:

A casement window AC can also be called a:

  • Vertical window air conditioner, which is a reference to its shape being taller than it is wide
  • Horizontal window air conditioner, which is a reference to fitting in windows that open side to side, or horizontally, rather than up and down (vertically)
  • Casement air conditioner, because it they are commonly used in that type of window

Sliding window air conditioner, because they fit sliding windows that are quite wide

Vertical / Casement Window Air Conditioner Installation Overview

What’s the same? These units fit into the window opening and rest on the sill. Most of the unit is outside.

What’s different? Instead of having an edge on the top, like a standard window air conditioner, to rest against the inside of the sash, they have metal or plastic edges on the side – or in some cases a piece of plastic that fits over the unit to hold it against the insides of the window opening, preventing it from falling to the outside of the window.

Plus, there are no wings on the side to fill the gap. Instead, the installation kit that comes with your casement window AC will have material to fill the gap above the window. Generally, the kits consist of a plastic frame and flexible foam. You might have to cut the kit materials to produce a custom fit.

See the section below, How To Install A Window AC Unit In a Horizontal Sliding Window, for full details.

Sliding Window Air Conditioner Reviews

A limited range of window air conditioners for casement and sliding windows are made. Some of them are not high enough in quality to recommend them.

But our list contains highly rated models with proven performance and durability. There are 8,000 and 10,000 BTU models – manufacturers do not make vertical window air conditioner models in other sizes.

Remember 15 ½”: Regardless of their given width, the manufacturers of each recommend a window with a minimum opening of 15 ½” for these small vertical window air conditioner models.

#1 Koldfront CAC8000W 8000 BTU 115V AC

This is an 8,000 BTU Koldfront casement window air conditioner with basic features only. On the positive side, this is an Energy Star casement AC that delivers lower operating costs.

Compared with the Frigidaire model, it is an affordable sliding window air conditioner.

  • Width: 14.2 inches
  • Features: Full-function remote, Energy Saver mode, 3-speed fan.
  • Pros: Energy Star. Compact window AC.  Affordable. Positive ratings are 74% to 76%.
  • Cons: Doesn’t have a timer.

#2 Frigidaire FFRS0822S1 8000 BTU AC

This Frigidaire sliding window AC removes 8K BTUs of heat per hour, so does a good job cooling space up to 350 square feet.

It has a good group of features. Here are the key points to consider.

  • Width: 14.2 inches
  • Features: 24-hour timer, full-function remote, Sleep mode, Energy Saver mode, 3-speed fan.
  • Pros: Narrow window AC, has all the features needed for convenience and making the room comfortable. Positive ratings are 73% to 77%.
  • Cons: Nothing major. Energy Saver mode reduces cooling, but that should be expected. You might want to use plexiglass instead of the foam supplied to fill the gap between the top of the AC and the top of your window opening. Negative ratings are about 12% to 14%. Many of them have to do with the unit being dented upon arrival, something Frigidaire seems to have addressed with better packaging.

#3 PerfectAire 3PASC10000 Window AC

This 10,000 BTU casement window AC has a lot of features that improve indoor comfort. The remote includes a separate thermostat. This unit also has Follow Me mode (see the Koldfront AC description).

AC mode lowers the temperature. Fan mode moves the air and creates a little white noise.

Dry mode dehumidifies the room without cooling. It’s an ideal mode for cool, damp spring and fall days when you want to get rid of the clammy feeling. You can also choose Auto mode, which selects the best mode to meet the thermostat requirement based on indoor climate conditions.

  • Width: 14.5 inches
  • Features: Remote, auto-restart, Cool/Fan/Dry/Auto modes, Sleep Mode too, programmable timer.
  • Pros: This PerfectAire casement window AC is more compact than some 8,000 BTU models. It has the widest range of features available and is light. 67% to 70% of the reviews are positive.
  • Cons: Louder than most other casement window units. That is the biggest complaint, so this unit might not be the right choice for bedroom installation. About 15% of the reviews are critical.

#4 Frigidaire FFRS1022R1 10000 BTU AC

This is from the same Frigidaire series as the unit above but in the 10,000 BTU slider window air conditioner size.

The Frigidaire 10,000 BTU window AC for horizontal windows has a full range of convenience and comfort features including a 24-hour timer that allows you to program when the unit runs.

The timer allows you to leave home with the unit off, and if programmed, it will come on and cool your space before you arrive. That’s the best way to reduce energy use and still have a comfortable room or apartment.

  • Width: 14.5 inches
  • Features: Remote, Programmable timer, 3-speed fan with Auto setting, Cool, Fan Only and Energy Saver modes.
  • Pros: Good climate control features, affordable cost for a 10K sliding window air conditioner. 77% to 80% of reviews are positive.
  • Cons: About 15% of the reviews are critical. The biggest concern is that it might be damaged on deliver. You can return it to Amazon for replacement or refund, but that’s an inconvenience.

#5 Arctic King 10,000 BTU AC

This is the 10K BTU version of the Arctic King casement window air conditioner listed above. It operates on a standard 110-volt plug, so you won’t need to install a 220V outlet.

Like many window air conditioners, this one has a “slinger-up” ring that splashes water removed by the AC onto the outdoor coil/radiator for faster, more efficient cooling.

  • Width: 14.6 inches
  • Features: Remote, Follow Me mode on remote, multiple fan speeds, 24H timer, Auto/Cool/Dry/Fan/Sleep modes, dirty filter notification, Exhaust feature to remove polluted indoor air.
  • Pros: Good climate control features, affordable cost for a 10K sliding window air conditioner. 77% to 80% of reviews are positive. 70% of the reviews are positive.
  • Cons: Heavier than other 10K BTU gliding window models. Less than 20% of the ratings are critical.

#6 Keystone 10,000 BTU Slider/Casement Window AC

Keystone is a brand that “flies under the radar” sometimes, but it is growing in popularity. The manufacturer is known for quality appliances at affordable costs, and this one is no different.

And as noted in the review below, it comes with excellent consumer ratings. It’s a newer model too, so if you want the latest in sliding window AC technology, it is worth a look. 

Keystone 10,000 BTU
  • Width: 14.57 inches
  • Features: Remote, 3 fan speeds, Auto/Cool/Dry/Fan/Sleep modes, dirty filter notification, 
  • Pros: About 90% of users give this unit a positive rating, and that makes it one of the top rated sliding window air conditioners on the market. Features are about what you’d expect from good window ACs.
  • Cons: A few of the units arrive damaged from shipping, though still in working order. You have the option of returning it or using it as-is. This, of course, isn’t the fault of Keystone, but typically the shipping company. And by the way, this can be true of absolutely and product, especially heavy ones, shipped from any seller.

#7 Koldfront CAC10000W 10000 BTU 115V Casement Air Conditioner

The dehumidifier on this Koldfront window AC for sliding windows is useful on cool, damp days. It doesn’t cool off the room, but it does take the dampness/humidity out of the air, so the room doesn’t feel “clammy” anymore. 

That’s the value of ACs with dehumidifier mode – which is often referred to as “dry mode.” They are worth considering in climates with cool, damp spring and fall weather (or winter, if your climate is generally mild). 

Koldfront CAC10000W
  • Width: 14.5 inches
  • Features: Digital AC display for accurate temperature setting. Dehumidifier. 3 fans speeds for versatile cooling. Sleep mode included plus energy saver mode to lower energy costs. The remote has a 16-foot range, good enough for most rooms this sliding window AC is suitable for.
  • Pros: More than 90% of reviews from verified users are good or excellent. It has all the features you’d expect in a quality vertical window AC. Plus, it is a fairly new model, so has all the latest technology and efficiency features. 
  • Cons: While the energy saver mode reduces energy use – and therefore energy costs – you might find that it won’t adequately cool the space in very warm, humid weather. 

The Cooling Size Range For Vertical Window AC Is Narrow

The fact is that you only have two choices in casement window air conditioner size:

  • 8,000 BTU designed for 300-350 square feet. Ex: 15’ x 20’ / 18’ x 18’
  • 10,000 BTU for 400-450 square feet. Ex: 20’ x 20’ / 30’ x 15’ / 28’ x 16’

What if the room is smaller?

You have a few options.

First, if the room is quite hot – on a second floor and facing west or south, in other words, getting a lot of sun, then an 8,000 BTU unit might not be “too big” for the heat, even if it seems oversized for the square footage.

Secondly, you could run the AC on the low AC setting, and it probably wouldn’t be too cold.

Thirdly, consider a portable air conditioner. They are available in sizes for smaller rooms from 100 square feet to 300 square feet.

Suggesting a portable AC raises an obvious question…

Do Portable AC Window Kits Fit Sliding and Casement Windows?

Sliding, yes, but for a casement window, you will probably need a window kit designed specifically for them. Read on, because we have found one.

Sliding windows: They probably will, especially if you have or buy one with a kit that is adjustable in length. Worst case scenario is that you might have to modify its length slightly. Just as with an up/down sash window, close the sliding window to fit tight against the firm plastic piece that the hose fits into.

Most window kits are at least two pieces. You might have to tape the assembly together at the right length.

If you’re unsure if your portable AC window piece will work, consider this universal kit made to vent a portable room AC out a sliding window.

Casement windows: These present more of a challenge due to the way they operate.

No fear! We are always looking for useful products to make things work for our readers.

We have located a window kit to connect a portable air conditioner to a casement window. There are a few of them on the market – here is the best, a flexible cover that nicely bridges the gap and allows you to vent a portable AC out the window.

Notes – This alternative window kit will also work for most awning and hopper windows. You might have to use a little additional material to close gaps on whatever window you install it with, and it is affordable and effective.

How To Install A Window AC Unit In A Horizontal Sliding Window

Most of the kits included with sliding window ACs fit windows from about 38” to 40” tall. For example, the Koldfront 8,000 BTU unit in the list above fits windows with a maximum height of 39 7/16”. The PerfectAire 3PASC10000 unit has a max. window height of 39 1/2″.

My window is shorter – No problem. The kits are adjustable, so shorter is OK, as long as the window is the minimum height necessary. That information can be found on the Amazon product pages we’ve linked to above for each model.

My window is higher – You can install the window kit, but you will have to fill in the space above it using plexiglass or thick plastic and duct tape.  

Installation: The installation manual that comes with your vertical/casement/sliding window air conditioner should be quite detailed.

Installation varies slightly by manufacturer for narrow / small vertical window air conditioner units. But here are the main steps to follow for most brands.

1). Unpackage the AC to make sure all the parts are in the box including the window kit parts – and locate the installation manual or section within the owner’s manual.

2). Read over the installation section while examining the window kit, so that once you begin, you’ll already know what you’re doing.

3). Build the support platform using the pieces, usually 2, that are included, and place the platform in the window. It should slope slightly toward the outside, so that condensate from the AC will run outside. If the slope is wrong, adjust the support bar of the platform, and try it again.

4). Secure the platform in the window using the included screws. You should still be able to adjust its slope using an adjustment bolt on the top of the platform.

Drilling Tip: Mark the holes, take out the platform and pre-drill the holes. Then re-install the platform, and install the screws.

Siding Tip: To prevent the outside leg of the bracket from scratching your siding, place a piece of 1” x 2” wood between the bracket and siding. A small screw might be included to secure the wood and protect your siding.

5). Attach a bottom sealing strip, if included. This rubber-like strip prevents moisture and air from leaking into your home beneath the AC. If your kit doesn’t have one, you can attach foam weatherstripping to the bottom of the AC either at this point or once it is installed (more details later).

6). Install the window panel frame onto the AC. You might have to use a hacksaw or heavy-duty utility knife to shorten the side panels. Measure the height of the window from the platform you installed to the top of the window opening. Then, subtract the height of the AC. Your result is how long the sides of the window panel frame should be.

7). Place the window panel inside the panel frame – it should slide easily into the channel or grooves in the sides of the frame.

8). Attach any fittings or channels to the sides of the AC with the included fasteners.

9). Slide the adjustable legs of the panel frame down into the grooves or channels you just installed on the sides of the AC unit. The bottom of the panel should rest on top of the air conditioner.

Tip: Stop and evaluate:  First, there should be a platform and bracket secured into the windowsill. Secondly, the air conditioner should be on the floor or workbench with the window panel frame and panel secured to it.  

10. Attach weatherstripping to the back of the panel frame where it will contact the window jamb. If foam strips are included, you might have to cut them to fit each side.

11). With a helper, if needed, lift the sliding window AC into place, and set it on the bottom part of the window and tight against the side of the window frame, not in the center of the opening, as with a standard window AC.

12). Attach any security or locking brackets. Most sliding window AC installation kits come with optional brackets that can be used to prevent the AC from moving once in place. They provide safety for those in the house and help to prevent intrusion from outside the house.

Final Steps – Use weatherstripping to close air gaps. This will improve your indoor climate control when running the air conditioner, and it will run more efficiently when outside air isn’t leaking into the space.

Is there a Casement/Vertical Window AC with Heat?

No, unfortunately, there isn’t.

What are your best options?

1 – Buy a casement window air conditioner plus a space heater.

2 – Choose one of the portable air conditioners that have heat. This unit comes in two sizes that have heat.

3 – Consider a wall AC with heat. Also called through-the-wall air conditioners, these units fit into a custom-cut hole that is fitted with a steel sleeve for semi-permanent installation. This high-quality Koldfront unit comes in 4 sizes to consider from 8,000 to 14,000 BTU, each with a wall sleeve included.

As Casement ACs Are More Expensive, Can I Install a Standard Window AC in a Casement or Sliding Window?

Yes, but only, of course, if the standard window air conditioner isn’t too wide! And that’s a big “if.”

In our research of nearly every window air conditioner currently manufactured, we discovered that the minimum width for the narrowest units is 16” or 17” if you remove the wings/side panels.

With the side panels in place, minimum width for small window ACs is 23”.

And, of course, you will need to customize a window panel to fill the gap above and around the AC. Clear plexiglass is best, but clear plastic is also used a lot.

And you’ll need good duct tape and weatherstripping to make the fitting as airtight as possible.

Can I Install A Portable AC in a Casement or Sliding Window?

Yes. Each window type requires a different installation method. There are more details up the page under the heading Do Portable AC Window Kits Fit Sliding and Casement Windows?

Sliding: The portable AC window kit should be usable in a sliding/gliding/rolling window.

If the kit you have doesn’t work, then here is a universal kit designed specifically for sliding/gliding windows.

Casement: Portable AC window installation kits are not at all designed for casement windows. However, as noted, we did find this window seal that fits over the opening sash of a casement window and attaches to the window frame too, creating a fairly tight seal.

Comparing a portable AC to an air conditioner for sliding window – Noise and Efficiency: Portable air conditioners are generally quieter than most casement air conditioner models. They run at levels of 43 to 55 decibels, depending on the model and compressor type. Casement/vertical window air conditioner units have noise levels around 60 decibels or higher. On the downside, you will get better energy efficiency with a window AC than a portable AC.

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.

2 thoughts on “Top 7 Vertical Window AC for Sliding/Casement Window in 2024”

  1. The units say they are for left to right sliders. My windows open from the right to the left. Does that mean these units won’t work in my sliders?


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