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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. These are great to think about, so you can choose the air conditioner that will fit your needs.
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 your needs.
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.
Hands down, portable air conditioners are going to be the easiest to install if you have sliding windows. Once you learn the gist about what a window air conditioner is, you’ll realize that a window unit won’t do very well with 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 windows 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.
Related: Check out the best central air conditioners that feature high energy efficiency ratings.
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.
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.
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, can be installed in windows or through the wall for added versatility.
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. It’s probably a great through-wall air conditioner since it’s so versatile. 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.
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.
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. We also compared aluminum vs copper coils on air conditioners so you’ll see which one is the better buy.
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.
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.
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.
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.
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 in 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 a 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.
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.
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.
Award: BEST FOR OFFICES
WHY WE LIKE IT: A simple casement air conditioner without complicated controls that are perfect for offices up to 450 square feet thanks to 10,000 BTUs as well as three fan and cooling speeds.
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. TheArctic 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 a four-way air direction for better airflow. Standard features include 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.
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.
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.
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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.
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 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.
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.
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