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Central air is an excellent way to cool your home, but a window air conditioner is your second-best option if that isn't an option. Window ACs can cool any room with a single- or double-hung window. You can keep costs low when you choose an Energy Star*-certified unit. All of our window picks are certified.

Window air conditioners are safe and easy to install if you follow the manufacturer's instructions. Most models feature security brackets to keep burglars out and your AC in place.

If your window isn't suitable for a window unit, consider a portable air conditioner. We've listed our best portable air conditioner pick in this guide, but you can also check out our portable AC guide.

For this guide, we tested 13 window air conditioners and consulted with Enesta Jones, a spokesperson for the US Environmental Protection Agency (EPA). We put each unit through a series of objective tests. Additionally, we answer your air conditioner FAQs and define some common terms.

Learn more about how Insider Reviews tests and researches home products.

Best air conditioner overall: Friedrich CCF08A10A Chill Premier Smart Window Air Conditioner, $399 available on AJ Madison If you have a medium-sized room, the Friedrich CCF08A10A Chill Premier Smart Window Air Conditioner is your best option with its impressive cooling abilities, smart connectivity, and long warranty.

Best budget air conditioner: GE AHY08LZ EZ Mount Window Air Conditioner. $319 available on AJ Madison The GE AHY08LZ EZ Mount Window Air Conditioner is your best bet if you're looking for a cheap way to cool your room, with its low-decibel output, outstanding cooling, and easy installation.

Best energy-efficient air conditioner: Midea MAW08V1QWT U Inverter Window Air Conditioner, $359 available on Amazon The Midea MAW08V1QWT U Inverter Window Air Conditioner features a unique U-shape design that allows you to open the window when it's installed, and it's one of only a few ACs to earn Energy Star's "Most Efficient" certification.

Best air conditioner for small rooms: Haier ESAQ406TZ Window Air Conditioner, $399 available on Appliances Connection The Haier ESAQ406TZ Window Air Conditioner is ideal for bedrooms and home offices thanks to its ultra-quiet design.

Best air conditioner for large rooms: LG LW1517IVSM Dual Inverter Smart Window Air Conditioner, $529 available on AJ Madison The LG LW1517IVSM Dual Inverter Smart Window Air Conditioner provides an impressive combination of quiet operation, outstanding performance, and energy efficiency.

Best portable air conditioner: LG LP1419IVSM Dual Inverter Smart Wi-Fi Portable Air Conditioner, $668 available on Abt The LG LP1419IVSM Dual Inverter Smart Wi-Fi Portable Air Conditioner is a well-rounded, energy-saving unit that can be controlled by your phone or voice.

If you have a medium-size room, the Friedrich CCF08A10A Chill Premier Smart Window Air Conditioner is your best option with its impressive cooling abilities, smart connectivity, and long warranty.

Pros: Long warranty on the sealed refrigerant system, WiFi connectivity, fits a broad range of window sizes, performed the best in our cooling tests

The Friedrich CCF08A10A Chill Premier Smart Window Air Conditioner dropped the temperature the most of the 13 models we tested in our 650-square-foot testing room. The temp dropped 5.3 degrees in one hour. 

The simple installation only took 30 minutes. I spent 10 minutes of that time connecting to the app (iOS and Android.) The app works well, allowing you to control and schedule the Friedrich CCF08A10A from anywhere.

It is Energy Star-certified and was middle-of-the-road in energy use among the tested models. While running on high for an hour, it used 0.4 kWh*.

The Friedrich Chill Premier is what I use in my home office. I installed it next to my desk, and unless it's a sweltering day, I generally prefer to run the dehumidifier alone. Otherwise, it gets too cold for my comfort. The control panel seemed to work inconsistently midway through last summer, but the app adjusts the settings effortlessly.

At 56.3 decibels on high (louder than a refrigerator), the Friedrich AC is among the loudest we tested. It still registered a loud 54.8 on low. However, I didn't find it distracting at all while working. It helped drown out the noises outside.

The GE AHY08LZ EZ Mount Window Air Conditioner is your best bet if you're looking for a cheap way to cool your room, with its low-decibel output, outstanding cooling, and easy installation.

Pros: Energy Star-certified, performed well in cooling tests, easy to install, quiet operation

Cons: Unable to access smart features, unimpressive CEER rating, minimal warranty

The GE 8,000 BTU Smart Window Air Conditioner (model AHY08LZ) features a relatively light weight of 54 pounds and is simple to install. I had it up and running within 20 minutes of opening the box, and it fit my slender 24-inch-wide window frame.

More importantly, it's a workhorse. In our test room of 650 square feet — nearly twice what the unit is rated for — the GE was able to decrease the temperature by more than 3 degrees in an hour. It did this while remaining fairly quiet, registering only 55 decibels on high, which makes it suitable for bedrooms and home offices.

Its control panel shows the temperature in large, easy-to-read numbers and automatically dims to keep light to a minimum if you're using it in the bedroom at night. The face also features adjustable louvers that allow you to send cool air precisely where you want. 

The GE has Wi-Fi connectivity and can be operated remotely, but I could not get it to connect with GE's Comfort app (available for iOS and Android). After several tries, I still couldn't use any of the smart features. Based on the 2.6-star rating in the Google Play store and 1.3-star rating in the App Store, I'm not alone. 

I reached out to GE about the app issues, and it responded quickly. According to the company, it's a known issue for some users but it did not have a timeline for when it would be fixed. However, even without the smart features, this is an outstanding unit.

The Midea MAW08V1QWT U Inverter Window Air Conditioner features a unique U-shape design that allows you to open the window when it's installed, and it's one of only a few ACs to earn Energy Star's "Most Efficient" certification.

Pros: Unique U-shaped design, Energy Star "Most Efficient" certification, easy to install in a wide array of windows, comes with a support bracket, quiet 48-decibel operation, smart connectivity that works well

Cons: Can only change airflow direction horizontally

The Midea MAW08V1QWT U Inverter Window Air Conditioner has a unique U-shaped design that offers more secure installation when combined with the included support bracket — hardware rarely included with AC units — and allows you to open and close the window to let in fresh air. 

It's the first window AC to receive the Energy Star "Most Efficient" certification, and it remains one of only a few models to receive that designation — another is the LG Dual Inverter AC, our pick for the best AC for large rooms. 

The Midea U uses inverter technology to achieve such impressive efficiency numbers. Inverter compressors have variable-speed motors that adjust to maintain the desired temperature. This constant low-level operation is actually more efficient than cycling high output on and off like traditional units do. According to my smart plug, the Midea U consumed 9.6 kWh over a 24 hour period, which works out to 0.4 kWh each hour.

Installation was quick, though the instructions could be a bit clearer. Still, I had the unit up and running within 25 minutes of opening the box. Connecting to the smart app was also quick and let me control the Midea U with my voice using Alexa.

I was impressed with how quietly the AC runs. The sound meter registered 48 decibels when it was operating on its highest setting. 

The only reason the Midea U isn't our top overall pick is its lukewarm performance in our cooling tests. It only decreased the temperature of our 650-square-foot room by 1.7 degrees in the first hour — comparable to our budget pick. 

The Haier ESAQ406TZ Window Air Conditioner is ideal for bedrooms and home offices thanks to its ultra-quiet design.

Pros: Good cooling for its size, quiet operation, easy installation, seemed to improve air quality during testing, Energy Star-certified, multi-directional vent control

Cons: Requires a window width of at least 26 1/16 inches, minimal/standard warranty

The Haier ESAQ406TZ Window Air Conditioner registered the lowest noise output of any of the units in our testing. On low, our sound meter measured 41.9 decibels, which is almost as quiet as a library. Even on high, it was only a little louder than a normal conversation at 51.4 decibels. Coupled with the low Btu output, this is the ideal unit for bedrooms and home offices.

Installing the Haier AC was relatively easy and didn't require any special steps. The process took me about 25 minutes. However, I found it surprising that such a low-Btu unit would require such a wide window opening.

The Haier was in the middle of the pack in cooling. It brought the room's temp down by about 2 degrees in one hour. This is impressive considering it was one of only two units with less than 8,000 Btu that I tested. (The other, the GE AHQ06LZ, did a much poorer job.) I like that there are multi-directional vent adjustments so you can send the cool air where you want it most.

During testing, I used a handheld monitor to measure any changes to air quality, and it showed a significant reduction in VOCs and particulate matter.

Lastly, it's Energy Star-certified, and that lined up with my experience with it. After an hour, it had used 0.3 kWh of electricity. It has an estimated yearly energy cost of about $52 according to government data.

The LG LW1517IVSM Dual Inverter Smart Window Air Conditioner provides an impressive combination of quiet operation, outstanding performance, and energy efficiency.

Pros: Good performance in our cooling tests, quiet operation, certified Energy Star "Most Efficient," Wi-Fi connectivity with support for Alexa and Google Home, can be controlled remotely with a smartphone app

Cons: Pain to install, underwhelming one-year warranty, only works in windows at least 27-inches wide

This LG unit was one of the best in our cooling tests, dropping the temperature in a 650-square-foot room by 3.3 degrees in one hour. It was also one of the quietest, registering just 53 decibels when on high. 

LG was the first to use inverter technology in its air conditioners. The dual-inverter compressor of the LG LW1517IVSM Dual Inverter Smart Window Air Conditioner helped it earn the rare Energy Star "Most Efficient" certification.

This is the main air conditioner I use on the ground floor of my home. Even on the hottest days, the LG LW1517IVSM keeps us cool. And, it remains quiet enough to facilitate normal conversation.

Installation was difficult, however. It took me two hours and included steps like removing and reinstalling parts from the unit. Uninstalling it for the winter was a task. Usually, I can carry air conditioners on my own, but I had to enlist the help of my teenage son when putting it in storage.

The LG can used with Amazon Alexa and Google Assistant . You can also use LG's SmartThinQ app (iOS and Android) to schedule the unit and perform other remote operations.

Read our full review of the LG LW1517IVSM Air Conditioner here.

The LG LP1419IVSM Dual Inverter Smart Wi-Fi Portable Air Conditioner is a well-rounded, energy-saving unit that can be controlled by your phone or voice.

Pros: Can be controlled and scheduled using your phone, voice control, easy to move, performed well in cooling tests, fits a wide array of window types and sizes

Cons: Set up took longer than others, one-year warranty, terrible energy efficiency compared to window ACs

*Editor's note: This model frequently goes in and out of stock at many retailers. We'll continue to update this post with availability.

Portable air conditioners have their benefits: namely portability and the ability to work with any outside opening. However, they vastly underperform compared to window ACs and no portable models are currently certified by Energy Star. While window AC units suck in hot air and vent it directly out the window, portable ACs rely on a long tube to carry air from your room to the outside. Along the way, heat radiates from the tube and stays in the room, so it takes a lot more energy (and money) to cool a room with a portable AC than a window AC. 

If you have a window that will accommodate it, we always recommend a window unit over a portable model. If that's not an option, however, the LG LP1419IVSM Dual Inverter Smart Wi-Fi Portable Air Conditioner is your best bet.

The LG portable AC is our top pick from our guide to the best portable air conditioners because it's quieter and more efficient than most portable models due to its dual-inverter compressor. It'll take about double the time to cool a room than a window unit, but it's very easy to install and use. 

After an initial 30-minute installation time (including connecting to the app), it was super simple to move from room to room. It only took about a minute to reinstall it in a new room thanks to its handles, smooth casters, and a dedicated slot for the window slider when in transport. We like that it can accommodate a wider range of windows than the other units in this guide.

It's Alexa-enabled and also has smart capabilities through the LG ThinQ app (iOS and Android), which lets you schedule when the unit runs.

Check out our guide to the best portable air conditioners.

We've tested 10 air conditioners over the last year, and there are several that barely missed the cut for our guide but are worth considering.

LG LW1216ER Window Air Conditioner: I kept this air conditioner installed in my family room last summer, and it did a great job of keeping my us cool while operating quietly enough to allow for TV viewing. It didn't displace any of our picks because it used a lot of energy, was a pain to install, and just didn't have any features that set it apart. Still, it's a good, reasonably priced option for medium-to-large rooms.

Friedrich CCW08B10B Chill Premier Series Smart Room Air Conditioner: Of the window ACs we tested to update this guide, this Friedrich did the best job in our cooling test, dropping the temp by 4.1 degrees. I like that the sealed refrigerant system is covered by a 5-year warranty, and the smart features worked as advertised. We didn't make it one of our picks because it's loud, uses a lot of power, and is pricey for an 8,000-Btu unit.

LG LW8021HRSM Window Air Conditioner: This AC has a unique design. The controls are on the bottom right of the face with the vent also along the right, rather than the standard of both being on the top. It pairs with the useful LG ThingQ app, operates quietly, did an adequate job of cooling, and was a quick install. It isn't a top pick because of its high power consumption, and it's pricey for such a low Btu unit.

Frigidaire FHWW083WB1 Smart Window Air Conditioner: There's a lot to like about this AC, but I couldn't find a category that it was tops in. It did well in the cooling tests, the app works well, it fits a broad range of window sizes, and it seemed to improve the air quality while operating. The negatives are that it's kind of loud and wasn't particularly energy-efficient.

Windmill Smart Window Air Conditioner: This was the loudest AC I tested at 63 decibels on high. It was also among the biggest power users and isn't Energy Star-certified. Plus, you can't adjust where the air flows. 

Friedrich Kuhl Series KCQ08A10A Window Air Conditioner: This AC performed poorly in our cooling tests, and I spent half an hour trying to get the weird browser-based Wi-Fi connectivity to work without any success. At this price point, there are much better options out there.

GE AHQ06LZ Window Air Conditioner: The only positives with this unit are it fits a wide range of window sizes and it doesn't use much power. It did the worst in our cooling tests, only has bidirectional vents, and it seemed to have a negative impact on air quality.

GE PHC08LY Profile Smart Window Room Air Conditioner: This was the runner-up in our cooling test, decreasing the room temp by 5 degrees in an hour. However, it used a ton of power and only has left/right vent control and not up and down.

I tested 13 window air conditioners to determine the best. I also consulted Enesta Jones, a US Environmental Protection Agency (EPA) spokesperson. The EPA oversees the Energy Star program. Our picks are energy-efficient, have helpful features, and performed well in our tests.

Here is how we test the main attributes we look for:

Installation: You'll probably only install and uninstall your AC once a year, but it can significantly impact your unit's performance. I timed how long it took to install each model, noted if I needed special tools, and assessed how easy it was to uninstall. I also looked at the window sizes each air conditioner would fit. Most will fit windows 27 to 36 inches wide. 

Cooling: I set up a digital thermometer on the opposite side of a 650-square-foot room from the air conditioner and determined its cooling capabilities by comparing the temperature before and after running the AC on its highest setting for an hour.

Noise: I took a decibel reading using a sound meter positioned 6 feet away from the AC running on high. I also noted any jarring sounds as the compressor turned on and off.

Air quality: Using an air quality monitor, I measured the particulate matter and volatile organic compounds in the air before and after running the AC for an hour. I noted any significant changes in air quality in our reviews, but the air quality never entered the "harmful" range during the tests, and I don't weigh this category heavily.

Power use: Using a smart plug, I measured how many kWh of power each unit used when on high for an hour. 

Extras: Almost all ACs come with fan and dehumidifier modes, a window installation kit, a delayed on/off function, and a remote control. These are the basics. We give extra points if a unit comes with foam seals, curtain insulation, WiFi connectivity, or other bonuses.

When shopping for an AC, there are four primary factors: Btu, room size, window size, and extra features.

The room size and window size entirely depend on your space, and the extra features depend on your personal preferences.

One thing you can't compromise on is the Btu of your air conditioner. For maximum cooling and efficiency, you need a unit that isn't too big or too small for your room size.

If you get a unit that is too big for your room, it will cool too quickly without removing the moisture, which will create a cold, clammy environment. Alternatively, an AC that is too small will be overworked, boosting your energy bills. Use the table below (from the Energy Star website) to determine what Btu your room requires:

Your Btu needs will be greater if the room has a ceiling more than 8 feet high, is very sunny, is regularly occupied by more than two people, or it's a kitchen.

It's common for model numbers for the same units to vary by one or two digits. This usually denotes different Btu ratings and colors, so choosing a model number that reflects the Btu rating right for your room is crucial.

Enesta Jones, a spokesperson for the EPA, which manages the Energy Star program, recommends you keep the unit level, circulate cool air with a fan, keep heat-producing objects away from the AC thermostat, and use a low fan speed on humid days.

You can also save on energy costs by installing your air conditioner in a shaded spot and keeping the thermostat as high as is comfortable.

Yes. However, the hot air your AC produces needs a way out of the room. Otherwise, you'll cancel out your unit's cooling effects. If you don't have a window, pick an AC that sends its hot air out the back. You can install these in an exterior wall.

You have more options with a portable unit since the opening to the outdoors only needs to be as large as the exhaust hose.

According to Jones, window ACs are more efficient than portable units, which aren't part of the Energy Star program. We found this to be true in our testing. The most efficient portable AC in our tests used 60% more energy than our top window pick.

Portable ACs are great in spaces where there isn't a window that can support a window air conditioner. But, in general, if you have a single- or double-hung window, use a window unit for better cooling and efficiency along with lower upfront and long-term costs.

If your AC has too many Btu for your room, it will cool faster than it can dehumidify, creating an uncomfortable, clammy environment. Consider purchasing a dehumidifier to remove access moisture, or replace the AC with a more suitable unit.

Another solution is increasing the space you are cooling. You can do this by keeping internal doors open. 

Smart ACs have WiFi connectivity that allows you to use your phone to schedule and control the unit remotely. You can crank the AC before you get home or turn it off after you leave to save energy. Many pair with smart speakers for voice operation.

Smart ACs don't always work as advertised. In our reviews, we note whether or not smart functions work well. In general, though, you're probably better off using a remote control, offered with all of the ACs in our guide.

You can enjoy some smart features by connecting your air conditioner to a smart plug. We use the BN-Link WiFi Smart Plug Outlet in our testing because it's affordable and gives energy consumption readings.

In the heating and cooling industry, there's a lot of jargon to wade through. What do all of those acronyms and terms even mean? Here are the definitions for a few that you'll commonly hear:

Btu: This is short for British thermal units. One Btu is equal to the amount of heat needed to raise 1 pound of water by 1 degree Fahrenheit. In cooling, Btu is used to measure how much heat is removed from a room. The more Btu per hour an air conditioner is rated for, the better job it does cooling.

CEER: "The CEER, or Combined Energy Efficiency Ratio, is a measure of energy efficiency for a room air conditioner," Jones says. "The higher a room air conditioner's CEER value, the more efficient the room conditioner is when comparing across models with the same cooling capacity." The CEER is measured by dividing the Btu output by the amount of energy consumed both while the unit is running and while it's in standby mode.

Compressor: The compressor works to push the hot air outside so cold air can circulate in your room. The gas refrigerant within the cooling system takes on the heat from the air, and the compressor turns the hot gas refrigerant back into a liquid. It works with the condenser on the air conditioner's hot side to dissipate the heat from the refrigerant. Along with the condenser and evaporator, the compressor is one of the three main components of any air conditioning unit.

Energy Star: This is a program run by the US Department of Energy and EPA to promote energy efficiency. "Any window AC model that earns the Energy Star label is independently certified to save energy, save money, and help protect the climate," says Jones. 

kWh: This is short for kilowatt-hour. It's a unit of energy that most electricity utilities use to measure your power use, and it's what we use to measure the energy consumption of the air conditioners we test.

More often than not, you want cool air without thinking twice — but a good discount does sweeten the deal. Air conditioner discounts are few and far between, with most big drops populating during holidays like Presidents' Day, Memorial Day, Black Friday , and Cyber Monday . Oftentimes, the best time to buy is during the off-season; the Friedrich Chill Premier, for example, was $50 off for half of March from Amazon. 

To make your home environment more comfortable, pick up one of our discounted air conditioners below during Amazon Prime Day. With many on the market, we pulled selections fit for small and large spaces alike.

Read more about how the Insider Reviews team evaluates deals and why you should trust us.

Sign up for Insider Reviews' weekly newsletter for more buying advice and great deals. You can purchase logo and accolade licensing to this story here. Disclosure: Written and researched by the Insider Reviews team. We highlight products and services you might find interesting. If you buy them, we may get a small share of the revenue from the sale from our partners. We may receive products free of charge from manufacturers to test. This does not drive our decision as to whether or not a product is featured or recommended. We operate independently from our advertising team. We welcome your feedback. Email us at reviews@insider.com.