When you’re shopping for the best air conditioner for sliding windows, you’ll need to think about whether you want a mounted window AC or a portable air conditioner. Always think about the size of the space you want to cool and pick a unit with a BTU rating that is compatible with that space. Next, think about energy efficiency as well as how easily a unit can move air through the room — known as the CFM. Finally, consider whether you want additional features like a dehumidifier or a unit that can be window mounted or installed through the wall if you need more versatility.

After conducting thorough research through countless consumer reviews, we nominated the Honeywell MN10CESWW sliding window air conditioner as our Top Pick. Keep reading to learn more about our research criteria and to shop from our recommendations of the best air conditioners for any need.

Top 10 Best Air Conditioners for Sliding Window

 #1  Honeywell MN10CESWW Sliding Window Air Conditioner

Award: TOP PICK

WHY WE LIKE IT: A portable air conditioner with 10,000 BTUs that’s rated for rooms up to 450 square feet with a dehumidifier and a solid 11.1 SEER rating.

Pros
  • 10,000 BTUs
  • 3 fan speeds, and dehumidifier
  • 174 CFM, 11.1 SEER
Cons
  • Low evaporation rate of 2.75 pints/hr

Hands down, portable air conditioners are going to be the easiest to install if you have sliding windows. This is because the installation kit includes a narrow panel that can be configured vertically or horizontally. The Honeywell MN10CESWW is our Top Pick because we think it’s a solid choice for anyone who has sliding windows, wants to install an air conditioner, but doesn’t want to deal with the hassle of traditionally mounted window AC installations. With 10,000 BTUs, you can cool rooms from 350 to 450 square feet.

We like that this pick has an 11.1 SEER rating which is on the higher end for window air conditioner efficiency ratings. However, we did note that the 174 CFM rating is somewhat low within this product category. Likewise, while you do have a dehumidifier feature, it only removes 2.75 pints per hour, which is relatively low for this category as well. Still, you’ll get three fan and cooling speeds and a modern digital touch control panel, along with a remote. As is standard, the filter is removable and washable. The best portable air conditioners and heaters will also feature mesh or removable washable filters that keep the air clean.

 #2  Frigidaire FFRS1022R1 Sliding Window Air Conditioner

Award: HONORABLE MENTION

WHY WE LIKE IT: A powerful casement air conditioner that’s perfect for rooms up to 450 square feet with a solid 3.4-pint per hour evaporation rate and a low energy consumption thanks to a 10.4 EER rating.

Pros
  • Ideal for areas up to 450 sq. ft.
  • Includes dehumidifier for 3.4 pints/hr
  • 10.4 EER, 323 CFM
Cons
  • Higher noise output at 61dB

Frigidaire is another great brand that’s known for making home appliances that are designed to last. The FFRS1022R1 is a casement air conditioner that can offer 10,000 BTUs and cool rooms as large as 450 square feet. As is standard, the window air conditioner installation kit for sliding windows is included. We also like that you get a 10.4 EER. While that’s not the highest energy rating, it’s in the top range for this product category. But more impressive is the 323 CFM maximum output which ensures that air is efficiently being moved through the room.

Although this Frigidaire window AC has a higher noise output of 61 decibels at the maximum speed, you still get plenty of key functionality. This includes three cooling and three fan speeds, and a dehumidifier mode. The dehumidifier has an evaporation rate of 3.4 pints per hour, which is in the median range. And you’ll also get a removable filter that can be washed to ensure air quality. Feel free to also compare this Frigidaire model with the best LG air conditioners on the market.

 #3  Frigidaire FFRS0822SE Sliding Window Air Conditioner

Frigidaire FFRS0822SE Sliding Window Air Conditioner

Award: BEST QUALITY

WHY WE LIKE IT: A complete sliding window air conditioner kit that’s perfect for smaller rooms up to 350 square feet with a solid 263 CFM rating and a higher energy efficiency score of 10.9 EER.

Pros
  • 8,000 BTUs for up to 350 sq. ft.
  • 10.9 EER, 263 CFM
  • Lower noise output of 55.1 dB at maximum speed
Cons
  • Lower evaporation rate of 3 pints per hour

The Frigidaire FFRS0822SE sliding window air conditioner kit is another great option from a reliable home appliance brand. This model offers 8,000 BTUs of power to cool rooms as large as 350 square feet. You’ll also get a 10.9 EER rating which is on the higher end for energy efficiency in this product category. We like the 263 CFM rating which is fairly efficient at moving air through a room. And with a decibel output that ranges from 48.4 to 55.1 decibels depending on the speed setting, this is one of the quietest options that we found in our research.

You’ll like that this is a three-in-one casement air conditioner that includes cooling, a dehumidifier, and a fan. The dehumidifier can remove up to three pints per hour. Compared to evaporation rates with competitive products, it’s in the medium range for efficacy. But that still amounts to a maximum of 72 pints of water removed from the air for someone who runs their air conditioner all day. Other standard features include a sleep mode and an energy-saving option. You may compare this with other energy-efficient units from the best window air conditioners.

 #4  LG LP0817WSR Air Conditioner

Award: BEST FOR SMALL ROOMS

WHY WE LIKE IT: One of the best portable air conditioners with a streamlined control panel that’s perfect for small rooms thanks to the 8,000 BTUs designed to cool rooms up to 200 square feet.

Pros
  • Streamlined LCD temperature control panel
  • 8,000 BTUs
  • 8.2 EER, 220 CFM
Cons
  • Doesn’t support smart integration

If you don’t know how to install a portable air conditioner in a horizontal sliding window, it’s easier than you think. The installation kit comes with a panel that easily fits for sliding windows. If you have a smaller room, you’ll appreciate the LG LP0817WSR. We think it’s one of the best portable air conditioners from our research because it’s budget-friendly while being effective and easy to install. You’ll get 8,000 BTUs to cool smaller rooms up to 200 square feet. Because it’s a portable air conditioner, it can work with vertical windows too.

You’ll get 8.2 EER for energy efficiency, which is in the medium range, along with a 220 CFM. But you’ll like the sleek design which includes a control panel with an LCD temperature display. The LG portable window AC unit is a three-in-one solution that includes cooling, a dehumidifier, and a fan function. The dehumidifier can remove up to 3.8 pints per hour, which is one of the highest we’ve seen in the sliding window category. You also get two fans and two cooling speeds. As for the best windowless air conditioner, you will need one that’s compatible with your dimensions and renovation limitations.

 #5  PerfectAire Sliding Window Air Conditioner

Award: BEST INSTALLATION

WHY WE LIKE IT: A vertical air conditioner with a smart Follow Me feature that relies on the remote’s location to gauge temperature, that can be installed in windows or through the wall for added versatility.

Pros
  • Includes Follow Me function for better cooling
  • 10,000 BTUs for 400 – 450 sq. ft.
  • 10.4 EER
Cons
  • Louder noise output at 61dB

Not everyone likes the idea of limiting window functionality by installing a window air conditioner there. So, we’re including the PerfectAire vertical air conditioner because it’s designed so that it can either be installed in a window or through a wall. While you’ll need to make sure you also have a sleeve to support proper installation, we think this versatility gives this pick an edge up on the competition. With 10,000 BTUs you can cool rooms from 400 to 450 square feet. This model has a 10.4 EER which makes it fairly efficient.

We also like that it comes with a Follow Me function. This is important because it means that your air conditioner is gauging the temperature based on where the remote is in the room, rather than solely reading the temperature of the air immediately around the unit. As is fairly standard, you’ll get three cooling and three fan speeds, along with a sleep and energy efficiency mode. Note though, that this is one of the louder units with a 61-decibel rating when set to maximum output. You may prefer the best tower air conditioner that features a low sound output and white noise functionality.

 #6  Koldfront CAC8000W Sliding Window Air Conditioner

Award: BEST SETTINGS

WHY WE LIKE IT: A horizontal sliding window air conditioner kit with 8,000 BTUs and a smart Energy Saver mode that helps reduce power consumption while maintaining a comfortable room temperature.

Pros
  • 11 EER, 235 CFM
  • Low 55 dB output
  • 8,000 BTUs
Cons
  • Brand fails to provide specifications for evaporation rate

For most people, outside of housing expenses, their energy bills represent the next largest expense for the home. So, energy efficiency and a smart energy saver mode that can help to better control energy consumption are essential features to keep in mind. The Koldfront CAC8000W window air conditioner comes with a horizontal sliding window air conditioner kit. You’ll get 8,000 BTUs that are rated to cool spaces from 300 to 350 square feet.

With 11 EER and 235 CFM ratings, this is a fairly efficient air conditioner solution. This casement window AC has one of the best Energy Saver and Sleep modes that we found in our research. Koldfront’s Sleep mode adjusts the temperature by two degrees periodically and then returns to the originally set temperature every six hours. Meanwhile, the Energy Saver mode cycles the fan for two minutes at 10-minute intervals until the ambient temperature rises above the temperature you originally set — at which point the cooling setting is triggered. With a 55-decibel output in the maximum setting, this is one of the quietest options for this product category. However, even though the brand promotes the dehumidifier setting, they fail to share the evaporation rate. For those that live in drier climates like the Southwest where the humidity levels are low, the best evaporative air conditioner is a perfect choice.

 #7  Midea KAW10C1AWT Sliding Window Air Conditioner

Midea KAW10C1AWT Sliding Window Air Conditioner

Award: BEST ENERGY EFFICIENCY

WHY WE LIKE IT: A highly energy efficient window AC unit with an 11.4 EER, 10,000 BTUs for up to 450 square feet of space, and four-way air directional controls for better comfort.

Pros
  • 10,000 BTUs for up to 450 sq. ft.
  • 4-way air directional controls
  • Includes washable filter
Cons
  • Higher noise output at 61dB
  • Only 1 cooling setting

We can’t stress enough that energy efficiency matters. And one of the best ways to make sure that your air conditioner doesn’t cause expensive spikes in energy consumption is to focus on the EER. This Midea KAW10C1AWT air conditioner has an 11.4 EER, which is one of the highest that we found from our research. You’ll get 10,000 BTUs of power which is rated to cool spaces up to 450 square feet.

This casement unit features four-way air direction for improved airflow. As is standard, this pick comes with a remote control, an energy saver mode, and a sleep mode. You’ll get a removable and washable filter for improved air quality. However, we did note that this pick only features one cooling speed but does have three fan speeds. For keeping cool while summer camping, you should take a peek at the best portable AC for camping.

 #8  Keystone KSTSW10A Sliding Window Air Conditioner

Keystone KSTSW10A Sliding Window Air Conditioner

Award: BEST FOR MEDIUM SIZED ROOMS

WHY WE LIKE IT: A solid air conditioner choice for people with rooms up to 450 square feet thanks to the 10,000 BTU rating and the 200 CFM and 10.8 EER ratings.

Pros
  • 200 CFM, 10.8 EER
  • 10,000 BTUs for up to 450 sq. ft.
  • 3 fan and 3 cool speeds
Cons
  • Lacks an auto shut-off feature

You’ll find that many window AC units are designed with medium-sized rooms in mind. The Keystone KSTSW10A casement air conditioner is a great option for rooms up to 450 square feet thanks to the 10,000 BTUs of power. With a 10.8 EER, this is a fairly energy-efficient option. While 200 CFM isn’t the highest option from our research — or even in our guide — it’s in the median range and should still be sufficient even for medium-sized rooms.

In terms of functionality, this Keystone unit offers competitive options like an energy saver and sleep mode. You’ll also get a remote control, as well as three cooling and three fan modes. While this pick lacks a timer, auto-shutoff, or app integration, we still think it’s a solid choice for anyone who needs a straightforward casement air conditioner that comes with an installation kit. These kits are important even when installing the best through the wall air conditioner.

 #9  Arctic King Sliding Window Air Conditioner

rctic King 10K BTU Air Conditioner Remote Slide Casement

Award: BEST FOR OFFICES

WHY WE LIKE IT: A simple casement air conditioner without complicated controls that’s perfect for offices up to 450 square feet thanks to 10,000 BTUs as well as three fan and cooling speeds.

Pros
  • 10,000 BTUs
  • Comes with a remote
  • 3 fan and 3 cooling speeds
Cons
  • Installation can be difficult and is best with two people

Office environments may not need an air conditioner with all the bells and whistles. Instead, they just need something effective at cooling a space while also being energy efficient. The
Arctic King AKSC10CR51 air conditioner gives you 10,000 BTUs of power which is rated to cool spaces up to 450 square feet.

This casement unit comes with the installation kit and offers four-way air direction for better airflow. Standard features include a remote control, energy saver mode, and a sleep mode. You’ll also have three fan speeds and three cooling speeds. And you can also remove the washable filter to improve air quality. Unfortunately, this brand failed to share important specifications such as the CFM, EER, or evaporation rate. And we did note through our research that trying to install this unit with just one person can be a chore. So, you’ll want to have an extra set of hands when you purchase this product. An installation kit would be great, like the one that comes with the best ductless mini split air conditioner.

 #10  Haier QPCA10YZMW Sliding Window Air Conditioner

Haier QPCA10YZMW 3-Speed

Award: BEST ON A BUDGET

WHY WE LIKE IT: An affordable portable AC unit that’s designed with an extended length window kit and 10,000 BTUs to cool rooms up to 350 square feet.

Pros
  • Includes extended length window kit
  • 10,000 BTUs for up to 350 sq. ft.
  • 230 CFM,
Cons
  • Low 6.8 EER
  • Low 2.7 pint/day evaporation rate

If you’re shopping on a budget but also need to buy an air conditioner for a sliding window, the Haier QPCA10YZMW portable air conditioner should be at the top of your list. This portable AC is designed with 10,000 BTUs of power to cool rooms as large as 350 square feet. With a 6.8 EER, that’s the lowest energy efficiency we found in our research. Likewise, while this pick does come with a dehumidifier, it only offers a low 2.7 pint per hour evaporation rate.

Still, you’ll get 230 CFM, which is fairly powerful considering the BTUs and compatible room size. Most importantly, this Haier pick comes with an extended length window kit that measures up to 48 inches, making it ideal for sliding windows. You’ll appreciate the LED control panel with capacitive touch, although you do get a remote control as well. You’ll have access to auto restart, a 24-hour timer, a removable washable air filter, and three cooling and three fan speeds. And the best dual hose portable air conditioner also has a carbon filter for improved air quality.

How We Decided

If you have horizontal sliding windows, you know that you can’t pick out a standard window air conditioner. Also known as a casement air conditioner, sliding window air conditioners are designed to be narrower to fit smaller dimensions. To create our guide for sliding window ACs, we focused on BTU ratings, design, efficiency ratings, programmability, and additional features.

You’ll find that all of the picks in our guide ranged from 8,000 to 10,000 BTUs. within this range, you’re most likely to efficiently cool rooms between 200 to 450 square feet. But to ensure the best airflow, look for models with higher CFM ratings. In our guide, the majority of the CFMs were between 200 to 250, which is fairly solid for window air conditioners.

Since none of our picks included supplemental heat, we solely focused on the EER/SEER ratings. In our guide, the energy ratings ranged from as low as 6.8 to as high as 11.4. As a general guide though, you should prioritize higher EER/SEER numbers as those will be more efficient.

But you should also consider the air conditioner design. With sliding windows, you don’t have to rely on a casement air conditioner that must be mounted. You can also opt for a portable air conditioner that comes with an installation kit that includes a panel. As long as you ensure the panel fits the height of your window, you should be fine.

And finally, we looked at programmability and additional features. Most of our picks came with a sleep mode and an energy saver mode, both of which can help to reduce overall power consumption. But we also focused on models that had a dehumidifier mode — also known as a dry mode. Where available we listed the evaporation rate which is always listed in pints per hour and references how much water the dehumidifier can remove from the air.

Best Air Conditioner for Sliding Window Buyer’s Guides

The Most Important Factors to Consider

  1. BTU Rating
    Begin with focusing on the BTUs or “British Thermal Units”. BTUs reference how effectively an air conditioner can heat or cool air within a specific amount of square footage. Larger rooms will require more BTUs. Depending on the space you need to heat or cool, you can find units with BTUs ranging from as little as 6,000 to as much as 36,000 BTUs.
  2. Design
    Air conditioners designed for sliding windows means that they’re going to be thinner and taller than a traditional window unit. This is because in this context, “sliding windows” means that your window opens by sliding horizontally (right to left or the reverse) as opposed to vertically (up and down).
  3. Efficiency Ratings
    There are a few key efficiency ratings that you need to prioritize — CFM, EER/SEER, and potentially the HSPF if you want an air conditioner with supplemental heat. The CFM or cubic feet per meter rating determines how efficiently air conditioners circulate air in a room. The higher the CFM rating, the better airflow a unit produces. The EER, SEER, and HSPF all determine the appliance’s efficiency at consuming power. Look for options that feature an Energy Star symbol. A higher figure means that an appliance is more efficient and is less likely to produce unexpected energy consumption spikes — assuming the wiring in your home or apartment is properly installed and maintained.
  4. Programmability
    While a control panel and remote are fairly standard, these days people may also want smart integration. This can include proprietary apps that allow you to monitor and adjust temperatures through your smartphone or smart assistant compatible units that can be paired with voice assistants like Alexa, Google Assistant, or Apple Home.
  5. Additional Features
    A nice feature that’s not required but helpful can be a dehumidifier. This function removes humidity from the air and can help to naturally reduce the temperature without running the cool settings at a higher level or temperature. Supplemental heat is another nice option that can be ideal if you live in a region where a traditional heating system isn’t necessary or the existing heater isn’t as efficient as you would like.

Air Conditioner for Sliding Window FAQs

Do portable air conditioners work with sliding windows?

The answer is it depends on the installation kit. Usually, a manufacturer will clarify whether a portable AC can be reconfigured to work with sliding windows. While sliding window air conditioners are usually designed to be thinner so that they properly fit in the slot, depending on your installation kit — or your ability to DIY a panel that will fit your window dimensions, you can install a portable air conditioner in a sliding window.

Is the higher the BTU better or worse?

As a general rule, higher BTUs are more effective at moving air than air conditioners with lower BTU ratings. However, the caveat is that you still want to make sure that you’re not investing in a unit that’s too powerful for the total square footage that you’re attempting to heat or cool. Picking a unit that’s too powerful can lead to excessive energy consumption that can overload electrical wiring and encourage shorts or power outages.

Is 6,000 BTUs enough for a bedroom?

This will depend on the square footage of your bedroom. But, on average, a 6,000 BTU air conditioner is rated to cool a room that is up to 300 square feet.

Can I leave a window air conditioner on 24 hours a day?

Yes, but there’s a catch. It’s more efficient — especially during warmer months — to keep your air conditioner on consistently to avoid overtaxing the unit. But, you can’t keep it running at full power indefinitely as this can lead to overcooling or using too much energy when it’s not necessary. For best results, you should use an eco or smart mode where the air conditioner reduces consumption once the desired temperature has been achieved and only works at more powerful levels when it detects a temperature change.

Dorian Smith-Garcia

Dorian Smith-Garcia is a bridal and beauty expert/influencer and the creative director behind The Anti Bridezilla. She is a diverse writer across beauty, fashion, travel, consumer goods, and tech. She also writes for Inverse, Glowsly, and The Drive along with a variety of other publications. When Dorian's not writing she's collecting stamps in her passport, learning new languages, or spending time with her husband and daughter.

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