Informational Guide

Window AC Guide

Read our quick & easy guide to the best window air conditioners. Learn how much cooling power you need & what type of AC unit is suitable for your room.

by Josh M

A hot day in a building without central air conditioning can get unbearable. Fans don’t help much, and most solutions seem very complicated and even more expensive, but neither you nor your wallet really need to suffer under the relentless summer heat.

Window air conditioners let you cool specific rooms, rather than your whole house, apartment or business space. It takes less energy to cool only the rooms that need cooling, than running a central air conditioner unit. This is an easy way to reduce your electricity usage.

A window air conditioner is a perfect choice if you want to cool a specific room, or a few specific rooms, and spend less on cooling costs. With adjustable thermostats, timers, and in some cases even Smartphone controls, these cooling units help you get the temperature you want. When you want it! Without wasting energy to keep the rooms cool at all times.

Find out if a window air conditioner unit is the right choice for you by looking at these pros and cons.

    • The popularity of window AC makes them easy to find and competition keeps the prices down
    • Relatively quiet and efficient
    • Drains water automatically
    • Fits in windows and wall holes
    • Rooms up to 300 square feet can be cooled even with small units. Larger ones work for rooms up to 650 square feet
    • With clever placement, it’s possible to cool more than one room

Window AC Disadvantages

    • The unit blocks an entire window when installed
    • Water dripping from the unit outside the window can land in inconvenient places (for example, on people)
    • Some windows are the wrong size for these units or otherwise can’t support them
    • Can be difficult to remove once installed
    • The included panels may let hot air through, reducing the unit’s efficiency.
Honeywell thermostat wall

Choosing the Right Window Air Conditioner

Finding the right window air conditioner for your needs is crucial and can make a big difference in both energy cost and comfort. Here are the key factors to look for.

Getting the size right is important. Units that are too small will have a hard time keeping the temperature down. Overly big ones, on the other hand, will be inefficient. Not only is it wasteful, the rapid cooling also means higher humidity, making the room feel moist and “clammy.”

Air conditioners typically need about 20 BTUs (British Thermal Units) per square foot. The typical cooling capacity of window air conditioners ranges between 5,000 and 14,000 BTUs per hour. Note that the size and weight of the unit increase with the cooling capacity.

Air conditioner energy efficiency is measured as EER (energy efficiency ratio). EER measures the ratio of cooling capacity (in BTu per hour) to power input (in watts). A higher EER rating means a more efficient air conditioner. An additional 1.0 of EER means 10% more efficiency, and lower operating costs. You can find information about a unit’s EER on the EnergyGuide label of the air conditioner.

Newer air conditioners cost less to operate due to higher energy standards in recent years. An EER of at least 12 is recommended. Keep an eye out for the ENERGY STAR label, which marks products that meet the strict guidelines for energy efficiency set by the U.S. Department of Energy and the Environmental Protection Agency.

Remember, higher EER means lower operating costs. On top of this, newer units conserve energy by shutting down when the room reaches the right temperature and starting again when it gets warmer, while older types keep the fan running and using electricity.

[Window air conditioner energy saving tips]

The unit must also fit your window. Carefully measure the inside dimensions, and keep in mind that the majority of window air conditioners are built for double-hung windows with a sash that can be raised or lowered.

Make sure that your electrical system meets the air conditioner’s requirements. Smaller units that draw less than 7.5 amperes work fine on any household electrical circuit, granted no other major appliances share the circuit. Larger units require their own 115v circuit, and the biggest ones need a dedicated 230v circuit.

Related ArticleUnderstand How a Window AC Work

Other Features to Consider

  • A programmable timer, to turn the unit on when it’s needed and off when it’s not, thus conserving energy and money.
  • Dehumidification capabilities differ between different models. You can find a rating, in pints and ounces per hour, of dehumidification.
  • Mechanical controls to let you adjust cooling level and fan speed.
  • Electronic controls let you set a target temperature for the unit to maintain.
  • An electronic ionizer makes the air conditioner better at reducing dust, pollen, and other air impurities.
  • remote control with a temperature sensor lets you set the air conditioner to activate when the temperature around the remote rises above the one you’ve specified.
  • Smartphone control allows you to turn the unit on or off and adjust settings from afar, so you can always come home to a cool room without running your air conditioner at all times. This is perfect if your schedule is irregular.
  • A removable filter makes it easy to keep the unit clean and at optimal capacity.
  • Filter alerts notify you when it’s time to clean the filter. Dirty filters make the unit use more energy for lesser results and may shorten its lifespan.
  • With an extra-long cord, it’s easier to reach a suitable power outlet.
  • Functions like “Turbo” and “Power thrust” help to push the cool air farther into long, narrow rooms.

Common Types of Window Air Conditioners on the Market

When you think “window air conditioner,” it’s normal to draw up images of those outdated, clunky window units that may be functional but aren’t necessarily nice to look at. Well, that’s all in the past because modern window ACs can give you the best of both worlds: high cooling performance and a design that won’t be an eyesore to the outside of your home.

When buying your new window unit, there’s a lot to think about. Besides the overall design, you also need to consider a unit’s physical size, BTU rating, and cooling features. Keeping all that and more in mind, we’ve compiled a comprehensive Buyer’s Guide to help you find the best window air conditioner on the market.

Small and compact window ACs are a great choice for small rooms, small windows, or anyone looking for a cooling solution that’s supplemental to a central AC system. Small units range in dimensions, but in terms of BTUs, they generally fall between the 4000 and 6000 rating.

Since this BTU range is on the low-end, small window units are best for small to medium-sized rooms. You won’t get an enormous coverage area; a quality compact unit is capable of cooling around 150 square feet and not much more than that, making it an ideal choice for small bedrooms, offices, and living areas.

Another thing to note about small units is that they’re great if you’re dealing with smaller-than-average windows. No matter what size window AC you’re looking for, paying close attention to dimensions is a big factor, and small units are ideal if your window frame measures less than 25 inches wide and 15 inches high.

Our Favorite Model

The key to choosing the right small window unit is to find one that’s small in size but not small in terms of performance. That’s exactly what you’ll get from the Frigidaire FFRA0511R1E, a compact 5000 BTU AC that offers some of the best cooling performance we’ve seen from a unit so small.

Another worthy contender for the best small window AC is Frigidaire’s FFRE0533S1, which is similar in design and style but goes above and beyond for energy performance. The EER for this one is an impressive 12.2, and the Energy Star certification will give you peace of mind knowing you won’t see a massive spike in electricity bills.

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Whether you need a cooling solution for a bedroom, an office, or a general living space, noise output is an important thing to think about. It’s inevitable that your AC will give off a gentle humming sound and will always deliver some level of white noise, but the thing to avoid is a unit that rattles, clunks, and makes other noises that will disrupt the peace.

Quiet window air conditioners usually have a decibel rating (AKA the overall noise output) between 40 and 50 dB. An output of 40 dB is about the same sound level as a library or soft bird calls, while 50 is more like a normal conversation. If quietness is a top priority, avoid anything above 60 dB – that’s getting up there on the decibel scale and will sound exponentially louder than a 40 dB unit.

One thing to keep in mind while shopping around for quiet window ACs is that the noise output will increase as you go up in cooling settings. So when a product says that it has a 40 dB output, check to see if that is for the low setting or the high setting. Even if the low setting gives off barely any noise at 40 dB, it won’t matter if the high setting has a 70 dB output.

Our Favorite Model

You won’t find a window unit much quieter than the Haier ESAQ406T. This 6000 BTU AC is part of Haier’s Serenity Series, and serenity is exactly what you’ll get. When set on low, the noise output is just 43 dB, and even with the quiet operation, you’ll get a fair amount of coverage area – it can handle up to 250 square feet of space.

Another pretty good option, if quiet is what you’re after, is the Frigidaire 8000 BTU window unit. Since it has a higher BTU rating, this is a great choice for larger rooms up to 350 square feet, and best of all, it’s still perfectly quiet at just 44 decibels.

Haier ESAQ406T Serenity Series 6, 000 BTU...
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One great thing about window units is that they’re generally more efficient on energy than portable ACs, and there are a lot of quality Energy Star rated energy efficient window ACs available. That’s good news since the Department of Energy claims that 6% of household energy costs go towards cooling the home.

Window units haven’t always been known for their efficiency, and in fact, it was just the opposite until recently. Within the past decade or so, window AC manufacturers have placed a larger focus on building highly efficient cooling solutions while not taking away from a unit’s performance. Many of these manufacturers have succeeded.

The tell-tale sign that a window AC performs efficiently is the Energy Star seal. ACs compliant with Energy Star standards use about 9% less energy than units without Energy Star approval, so that blue logo is the main thing to look out for. You can also get a good idea of a unit’s efficiency by considering the Energy Efficiency Ratio, or EER. An EER of 12 or above tells you that a window unit is efficient, but anything above 11 is still good.

Our Favorite Model

Keeping Energy Star compliance and EER ratings in mind, the most energy-efficient window AC that won’t cost much to run is the AMANA 5,000 BTU unit. This AC is Energy Star certified with an EER of 11, and best of all, it’s estimated to cost just $45 per year to run. That’s about $0.12 per day, and we can all agree that you can’t get much better than that.

The Amana AC is only suitable for rooms up to 150 square feet, so if you need something larger, you can go with the LG LW8016ER instead. Since this one is rated at 8000 BTU, it’s the more appropriate choice for rooms up to 340 square feet. The EER for this one is 12.1, but since it’s a bit larger, it’s estimated to cost slightly more to run (about $60 per year).

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Window units are often thought to only work well in small to medium-sized rooms, but many people don’t realize that the right unit could cool down a room (even an entire home) as large as 2500 square feet.

Window units for large rooms are the perfect solution if you don’t want to deal with the costly, time-consuming process of installing a central air system but also need something larger than the standard 5K, 6K, or 8K BTU AC. Larger units can have a BTU rating anywhere between 12K and 36K BTU, so just as you’d expect, they’re capable of cooling much larger square footage.

While some larger window units can cool around 450 square feet – which is still considered a very large room – others can handle upwards of 2500. Just be mindful that these units will cost more than the lower-BTU ACs, but the good news is that the cost is actually less when comparing it to buying multiple smaller units to handle the same coverage area.

Our Favourite Model

The model that stands out as the best large window unit for a greater coverage area is the Frigidaire FFRE2533U2, a 25000 BTU AC that’s ideal for up to 1600 square feet. The only negative feature of the Frigidaire is that it requires a 230v outlet, but that’s pretty normal for ACs this size.

The Emerson Quiet Kool EARC15RE1 is another option for large rooms, capable of handling 700 square feet quickly and quietly. It comes in a few different sizing options, but 15000 is the most popular EARC15RE1 BTU rating. The good news about this one is that it works with your standard outlet, so you won’t need a dedicated 240v plug.

FRIGIDAIRE FFRE2533U2 25,000 BTU 230V...
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  • Quickly cools a room up to 1, 600 sq. ft.

If your home has sliding windows, you might assume window ACs are out of the picture. That’s not the case, thanks to sliding window air conditioners built for casement windows that slide open from side to side instead of up and down. These units are taller and thinner than the standard window cooling fixtures, and since there’s no “standard” size for casement units, taking measurements before buying is a must.

When you compare horizontal to vertical sliding window units, there’s only one real difference, and that’s the shape. If you have sliding windows, you’ll actually find that installing a casement unit is easier since the tall-skinny design doesn’t require as much support.

Although the configuration is different, sliding window ACs are meant to be installed in a window space just like any other window unit. The cooling action happens by first activating a blower to get the air circulating, then once that air is moving, the compressor and cooling coil work to drop the temperature of the air before pushing back out into the space.

Our Favorite Model

Frigidaire makes a window unit for all different cooling needs and window designs, including a casement AC. The Frigidaire FFRS1022R1 is perfectly designed for sliding windows and made for easy installation. It’s powerful – 10000 BTUs – and can cool a room up to 450 square feet. Oh, and did we mention that it’s highly efficient with a 10.4 EER?

Another option that’s designed with casement windows in mind is the Koldfront CAC8000W. This one is slightly less powerful at 8000 BTUs, so it also has a smaller coverage area of 350 square feet. That makes it a great choice for medium-sized bedrooms and living spaces.

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Nowadays, many home appliances can connect to the internet, making the lives of homeowners easier. WiFi-capable ACs, also called Smart ACs, let you control all your cooling needs via a smartphone or tablet. That means you can adjust the temperature, change the fan setting, set timers, and more without ever needing to touch the unit’s console.

There are even some Smart ACs that can connect to popular home devices like Amazon Alexa and Google Home, so simply use your voice to control the unit. While some people don’t view smart functionality as a priority, others think that the added convenience factor is worth paying more.

Before purchasing your Wifi-enabled window unit, you’ll want to pay attention to all the usual buying considerations, like BTU, coverage area, and EER. From there, you can focus on the smart control functions, like whether the unit is app-enabled or can operate on voice command.

Our Favorite Model

LG is a leading brand when it comes to smart functionality, which is one of the reasons why the LG LW1019IVSM is our top pick. Reviewers seem to agree; this unit regularly gets 5 stars for being one of the most intelligent ACs on the market.

If you need more power than the LG’s 9500 BTU rating has to offer, the 12000 BTU Friedrich Chill Premier might be the better choice. This window unit offers built-in WiFi and can be controlled through an app, via the LED remote, or by pushing the control panel buttons. While the LG is best for 450 square foot spaces, this one works well in up to 550 square feet.

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Wall-mounted air conditioners, more commonly known as through the wall ACs, are very similar in design to window ACs but with one slight difference. Instead of mounting the unit within a window frame, it’s mounted quite literally “through the wall.”

There’s one big benefit that wall-mounting provides, and it’s that many window AC units vent their warm exhaust both out of the back and out of part of their sides. This isn’t a problem with through the wall units since all of the vents are secured behind a wall, therefore keeping all of the warm exhaust outside and preventing it from seeping back into the room.

The only real downside of this type of AC is that they’re not as easy to install as a standard window unit. You’ll first need to create the wall opening and then install the included AC sleeve before securing the unit into place, plugging it in, and turning it on.

Related ArticleSteps to Install an In-Wall AC

Our Favorite Model

The best-rated through the wall unit based on cooling performance and ease of installation is the Koldfront WTC12001W. It’s a powerful 12000 BTU AC that has a max cooling area of 550 square feet. The EER isn’t stellar at 9.5, but for a unit of this size and power, that efficiency rating is perfectly acceptable.

If you’re looking for a more energy-efficient solution than the Koldfront, there’s also the Friedrich CP08G10B. This one has an EER of 12.1, so the cost of running the Friedrich is estimated to be about half as much. However, the BTU is less at 8000, which means the coverage area is also a much smaller 350 square feet.

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Explaining BTU Sizes of Window AC Units

We’ve talked a lot about BTUs so far, so you’re probably already aware that the higher an AC’s BTU rating, the more powerful the unit. That’s the general rule of thumb, but let’s look at BTUs more closely for a better understanding.

According to Newair, BTU stands for “British Thermal Unit, though the term isn’t only used in the United Kingdom. It’s a measurement that’s part of the common system, along with things like pounds, inches, and degrees Fahrenheit…BTUs measure the amount of energy it takes to produce a certain amount of heat.”

For cooling and heating, the main thing to know about BTUs is that it tells you how powerful the system is. A small 5000 BTU AC can produce 5000 BTUs of energy within an hour, while a much larger 12000 BTU unit can produce 12000 BTUs of energy in that same hour.

Here’s a complete guide on what to expect from different BTU ratings for window ACs:

  • 5000 BTU Models
    A unit with a 5K BTU rating can handle around 150 square feet, making it a good choice for small rooms.
  • 6000 BTU Models
    6K BTU units can handle anywhere between 150 and 250 square feet, so it’s best for small and medium-sized rooms.
  • 8000 BTU Models
    An 8K BTU unit is best for medium/large rooms measuring between 300 and 350 square feet, while moving up to 9000 is better for a 400-square-foot space.
  • 10000 BTU Models
    10K BTU models are best for spaces measuring 400-450 square feet.
  • 12000 BTU Models
    If your space is between 450 and 550 square feet, you’ll want to go with a 12K BTU window AC.
  • 14000 BTU Models
    14K BTUs is best for rooms between 550 and 700 square feet. It’s a great choice for large rooms, but even some people with small enough apartments can fulfill their cooling needs with a 14000 BTU unit.
  • 15000 BTU Models
    15000 BTUs is ideal for rooms around 750 square feet. For anything larger than that, you’ll want to move up to 180000, which is the next common BTU size before hitting larger numbers, like 25K and 32K.

Room Examples and Recommendations

Bedroom (100 – 300 square feet)

For a small or medium size bedroom, you will need a unit with a capacity between 5,000 and 6,500 BTu/hr, and a low noise rating. Some units feature a sleep setting, which reduces noise and energy usage by running the fan less frequently to avoid excess cooling when you sleep.

Living Room (350 – 650 square feet)

A living room calls for a larger air conditioner. There’s more open space and it takes more to cool rooms that often contain more than two people. An extra 600 BTu/hr per additional person is recommended. This means you’ll want a capacity of around 9,800 to 12,500 Btu/hr.

Kitchen (150-250 square feet)

Kitchens can vary a lot in size and shape, but they tend to need quite strong units. An extra 4,000 BTu is recommended for a unit used in a kitchen, to compensate for the heat generated by the stove and other hot appliances. You’ll want a unit with a capacity in the range of 7000 to 9000 BTu/hr.

If you’re confused about the size of your room or your cooling needs, take a look at this cheat sheet and calculator for window AC capacity needs.

wifi air conditioner

Energy Efficiency of Room Air Conditioners

You can increase efficiency and comfort, and reduce energy costs, by ensuring optimal conditions for the air conditioner.

With proper placement and regular maintenance, the unit will perform better. Follow these directions to get the most out of your air conditioner.

  • A window in the shade is optimal, increasing efficiency by up to 20% compared to a sunny window. Windows facing north get the most shade.
  • The unit must be level to ensure proper function.
  • Make sure that nothing blocks the unit’s airflow.
  • High fan speeds are generally best, but on really humid days the slower settings are better for keeping humidity down.
  • Keep lamps, TVs, and computers away from your air conditioner. It will run longer than necessary if its thermostat senses heat from hot electronics.
  • Consider using an interior fan in conjunction with your window air conditioner to spread the cooled air through your home without greatly increasing electricity use.
  • Get help when installing. Window air conditioners are quite heavy.
  • Basic maintenance helps retain maximum efficiency in its lifespan. Here’s how to do it.
  • Optimal efficiency relies on proper air sealing and insulation. Energy Star recommends the following adjustments.

Following these tips and guidelines will help you find the perfect window air conditioner for your needs and keep your cool without paying too much. To learn more about cooling options in your home, check our favorite small portable ACs and quietest portable ACs.

Popular Brands of Window Air Conditioners

There are dozens of brands to choose from in the cooling industry, so choosing the right one is the first challenge to overcome. We’ve helped out by providing in-depth info on some of the most beloved brands on the market, so be sure to check out the comprehensive AC brand review guides.

Here’s a quick guide to some popular brands of window air conditioners in 2022:

  • Frigidaire
    It’s easy to sing the praises of Frigidaire when you consider the brand’s fair pricing model combined with its dedication to cooling performance. Their window units are some of the most efficient out there, and they offer a variety of different AC sizes/styles to choose from.
  • LG
    LG window ACs are some of the most advanced in terms of technology. It’s not uncommon to come across an LG unit that has WiFi capability and other smart features. That, combined with the sleek design of LG units, makes this brand another top pick for anyone.
  • GE
    GE will always stand out as one of the best home appliances manufacturers, and window ACs are no exception. Some people think that GE’s designs are a bit outdated, but overall, it’s hard to beat the affordable cooling performance that comes along with a GE window unit.
  • Haier
    Haier is more well-known for its range of portable ACs, but that doesn’t mean you should overlook their window units. Haier window-mounted ACs are designed to cool an entire room while also being easy to operate and maintain.
  • Friedrich
    This brand has been around for more than a century, so it’s obviously a name you can trust to keep you cool and comfortable in your own home. If you value convenience and quality, Friedrich is a brand to keep an eye on.
  • Koldfront
    While other brands specialize in different AC types, like portable or mini-split, Koldfront works strictly with window units. Their best-selling features are things like a 24-hour timer, dual functionality, remote control operation, and a sleek all-white design.
  • Amana
    Most people go with Amana for larger cooling systems for central air, but the brand’s window units are also worth considering. If you want something small and energy-efficient, the Amana 5000 BTU AC is a cost-effective solution. The brand offers a variety of different sizes, ranging from 5K all the way up to 24K.


While a window AC isn’t for everyone, there are a lot of benefits that come along with mounting your cooling system within a window. These units are highly efficient, plus they’re easy to install, and you’ve got a lot of options for choosing your ideal size based on the coverage area and your cooling needs.

Last Updated on April 18, 2022

Josh M

My name is Josh and I am obsessed with the HVAC industry. I created this website to help HVAC techs of all levels get the best out of their heating & cooling systems. I have spent thousands of hours studying air conditioners, heaters and home air products so you can learn & buy with confidence. Learn more about the team here.