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Published Jun 17, 2022 1:00 PM

No one wants to sit at home, sweating, on a sweltering summer day. For those of us who lack an air conditioning system, staying cool can be a challenging and expensive proposition. An energy-efficient air conditioner can help you keep your home cool while keeping your utility bills low. Listen. If you’re reading this, it’s probably hot out (or it will be soon). Do yourself a favor and let us guide you through the process of picking the best energy-efficient air conditioners for every person and space.

How we picked the best energy-efficient air conditioners

I live on the bottom floor in a small apartment with no central air conditioning. It can get hot in the summer, with temperatures in our bedroom generally hovering around 80 degrees. That’s not conducive to sleep and our standing fans don’t provide much respite. In other words, my air conditioner is very important. Therefore, I take buying a new one very seriously.

Our selections are the product of hours of research, including personal experiences, peer suggestions, user impressions, and the foundation we used for Popular Science’s previous air conditioner guides, including the best window air conditioners and the best portable air conditioners. I personally have over 10 years of experience covering consumer electronics for Popular Science, CNN Underscored, Gear Patrol, and XDA Developers, among others.

What to consider when picking from the best energy-efficient air conditioners

It’s easy to get blindsided when picking a new air conditioner. It’s one of those appliances that we don’t think about too much until they stop working. Before choosing the best energy-efficient AC unit for your home, it really helps to learn the basics—knowing the pros and cons of different air conditioner types and energy ratings will help you make an informed decision about balancing energy consumption and cooling power. We also considered factors like smart features and noise level, which can make a significant difference to the overall experience. 

One programming note: While central air will definitely keep any home cool, the installation is a very involved process that you should sort out with experts, including a contractor. This guide focuses on in-window air conditioning units and portable air conditioners, which you can buy as a quick and efficient way to cool a room or home without any major installation costs.

Window units vs portable air conditioners

Window and portable AC units offer roughly the same amount of cooling power for around the same price. However, they operate in different ways, which may determine whether one works better for you. Before making your choice, you should know what type of air conditioner you need to shop for.

An in-window air conditioner needs to be installed in a window, often using a bracket to keep it from falling out. Depending on the unit, you may be able to leave your AC in place all year round, or you may have to take out and reinstall it every year. Once installed, though, in-window air conditioners are almost always quieter than portable air conditioners and don’t take up any space in your home.

By contrast, a portable air conditioner usually needs to be in close proximity to a window but is far easier to move around. Simply plug it into an outlet and install a window kit to vent moisture and exhaust. Many portable ACs vent their exhaust through a hose, potentially giving you the ability to cool down a room with a smaller window that couldn’t hold an in-window model.

You definitely want to figure out whether you have a place to install an in-window or portable air conditioner before picking a unit. All things being equal, we’d usually recommend a window unit over a portable AC, but there are plenty of logistical factors that may lead you to go the other way.

How much power do you need?

Air conditioners come in many sizes, often based on their cooling capacity. To figure out what size air conditioner you need, you need to look at the size of the room or home you’re trying to cool. Measure the space to find out how many square feet you need your AC to cover. Energy Star’s buying guide features a geometry refresher to help people calculate a room’s area specifically for this purpose.

Once you know the square footage, you can determine how much cooling power you need from your air conditioner. Appliance manufacturers measure AC cooling power in British Thermal Units, commonly known as BTUs. According to Consumer Reports, you need 20 BTUs per square foot for the area you want to cool down. The amount of cooling power you need may vary beyond this basic calculation, though, based on room-specific factors such as sun exposure.

A 5,000 BTU air conditioner should have enough power to effectively cool 100-150 square feet, which is more or less the standard bedroom size in homes and apartments. To cool more than a single room, your power requirements climb: Realistically, you want 12,000-14,000 BTUs to cool 550-700 square feet.

There may be factors that prevent you from using an air conditioner large enough for your space. For example, your window may be too short or narrow to support a large window unit. While it isn’t always up to you, keep in mind that using an air conditioner that’s too small may reduce its effectiveness. Likewise, a large air conditioner may use more power than necessary when cooling a smaller room. 

Understanding energy-efficiency ratings

No matter what you do, your air conditioner is going to use a lot of power. We recommend picking an air conditioner with energy efficiency in mind for a variety of reasons, from saving money to minimizing the environmental impact of keeping cool. Air conditioners feature a number of energy efficiency ratings, which indicate certain thresholds for sipping power, rather than guzzling it. For the purposes of this guide, we’re going to focus on three energy standards: The Energy Efficiency Ratio (EER), Combined Energy Efficiency Ratio (CEER), and Energy Star certification.

The Energy Efficiency Ratio measures the ratio of an air conditioner’s output per hour, as measured in British thermal units (BTUs), to the AC’s power draw, measured in watts (W). The EER is used to measure the system’s overall efficiency, with a higher rating resulting in a more efficient system. For example, let’s say a 12,000 BTU air conditioner is powered by 1,000W. For every 1W of energy provided to the AC unit, we will get 12 BTU of cooling effect in return. That’s better than a 12,000 BTU unit powered by 1,400W, which would result in a less efficient rating of 8.57.

Combined Energy Efficiency Ratio (CEER) is a standard set by the Department of Energy (DOE) in 2014 that rates the energy efficiency of window-based air conditioners. The ratio shows the cooling capacity output, measured in BTUs, relative to the electricity use and standby/off-mode power consumption.

Some of the best air conditioners also have an Energy Star rating, indicating that they meet federal guidelines for energy efficiency and use 10 percent less energy than an AC unit that isn’t Energy Star-certified. In general, picking an Energy Star-certified air conditioner is the way to go. While window and central AC systems offer Energy Star ratings, no portable units are Energy Star-certified.

How loud is it?

All air conditioners are noisy. There’s no way around it, but that’s all the more reason to try and buy one that’s as quiet as possible. Most air conditioners feature an estimated noise level, measured in decibels (dB), to tell you how loud an AC gets at peak performance.

According to the Centers for Disease Control and Prevention, air conditioners often operate around 60 dB, which is “comfortable” to listen to over a sustained period. That said, the Environmental Protection Agency recommends limiting exposure to indoor noises above 45 dB. Of course, these statistics don’t factor in your personal tolerance for ambient noise. Ultimately, the best advice we can give is that you should look for an AC that runs quietly, especially if you’re buying an AC that you want to last, and avoid any unit that hits above 60 dB.

Are there smart features?

As with many modern appliances, many modern air conditioners feature nuanced controls and internet-enabled “smart” capabilities, such as the ability to set target temperatures and schedules or control the device through a smartphone app. These functions make your air conditioner more convenient and more efficient. Of course, these features are considered luxuries, so you may not find them on less expensive units.

The best energy-efficient air conditioners: Reviews & Recommendations

If you’re in a situation where fans alone cannot keep you cool, it may be time to get an air conditioner. Now that you know how to pick one, let’s talk about the best energy-efficient air conditioners you can buy today.

Best overall: Midea U-Shaped Air Conditioner (MAW08V1QWT)

Buy it used or refurbished: eBay

Why it made the cut: The Midea U will quietly cool down your space, thanks to its distinctive U-shaped design.

Specs

  • Type: Window
  • Energy efficiency: 15 CEER
  • BTUs: 8,000
  • Energy Star certified: Yes
  • Estimated noise level: 42 dB (low) – 47 dB (high)

Pros

  • U-shaped design
  • Quiet operation
  • Support for smart features

Cons

  • Difficult installation process

Most window air conditioners feature a box-style design. The Midea U-Shaped Air Conditioner takes a slightly different approach. It features a slot between its vents and the housing for most of its hardware. The shape lets you close your window and keep most of the air conditioner’s noise outside your home. It also lets you freely open and close the window without the unit falling out.

The Midea U also uses inverter technology, which helps better regulate energy flow to the unit based on demand. It received an extremely high 15 CEER score, which is incredible when you consider that most efficient units score an 11 or 12.

Lastly, the Midea U supports smart features so that you can set recurring schedules—and it’s compatible with Alexa and Google Assistant, allowing you to turn the unit on or off with your voice.

Finding an in-window AC unit with great design, intelligent features, and energy efficiency can be challenging. The Midea U hit all of those marks, making it a rare and exciting appliance.

Best window: LG Dual-Inverter 18K (LW1817IVSM)

Buy it used or refurbished: eBay

Why it made the cut: The LG LW1817IVSM is quiet, energy-efficient, and supports smart functionality.

Specs

  • Type: Window
  • Energy efficiency: 14.7 CEER
  • BTUs: 18,000
  • Energy Star certified: Yes
  • Estimated noise level: 44 dB (sleep mode) – 59 dB (high)

Pros

  • Quiet operation
  • Capable of cooling off large spaces
  • Smart feature support

Cons

  • Pricey

If you need a powerful air conditioner that cools a whole apartment or floor of your home, the LG LW1817IVSM is a high-powered window unit. Like our top pick, it features inverter technology, which makes it especially quiet and efficient for its size. It provides 25-percent more energy savings than the Energy Star certification requirement. It has a CEER of 14.7 and pumps out up to 18,000 BTUs, allowing it to cool spaces up to 1,000 square feet. Meanwhile, it keeps comparatively quiet, hitting just under 60 dB at high power and shushing down to just 44 dB in a specialty sleep mode.

In addition, the LW1817IVSM supports a smartphone app that allows users to set schedules and turn the unit on or off remotely. It also supports Alexa and Google Assistant for hands-free control. These features make LG’s air conditioner easy to use, allowing you to effortlessly stay cool, rather than fiddle around with settings.

Best portable: Whynter ARC-14S

Whynter

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Buy it used or refurbished: eBay

Why it made the cut: The Whynter ARC-14S portable air conditioner features a slick design and convenient auto-drain technology.

Specs

  • Type: Portable
  • Energy efficiency: 11.2 EER
  • BTUs: 14,000
  • Energy Star Certified: N/A
  • Estimated noise level: 56 dB

Pros

  • Slick design
  • Capable of cooling large spaces
  • Auto-drain technology

Cons

  • Loud

Portable air conditioners often don’t meet the same specs as window units, but the Whynter ARC-14S comes close. It offers a respectable 11.2 EER rating while pumping out an impressive 14,000 BTUs of cooling power. That makes it one of the most energy-efficient portable air conditioners on the market.

It also offers some convenient features, including an auto-drain function that recycles captured moisture to create more cool air. This not only helps your room cool, but it means you don’t have to worry about emptying out a moisture tank (a common feature on portable AC units). It also features a dual-exhaust design, improving its ability to cool your space. As far as portable air conditioners go, the Whynter ARC-14S hits all the right notes with its design, features, and energy efficiency.

Best design: Windmill AC

Windmill

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Buy it used or refurbished: eBay

Why it made the cut: The Windmill Air features an attractive design and an app that lets you control the AC unit remotely.

Specs

  • Type: Window
  • Energy efficiency: 11.9 CEER
  • BTUs: 8,300
  • Energy Star Certified: No
  • Estimated noise level: 50 dB (low)

Pros

  • Great design
  • Smart home features
  • Easy to install

Cons

  • Unable to control the direction of the fan
  • Not energy star certified

Air conditioners are generally an eyesore. They’re big … they’re bulky … they’re hanging out our windows or taking up space in the corners of our rooms. The Windmill puts a little bit of extra care into AC aesthetics, with rounded corners and a clean, pleasing front vent. Windmill also prides itself on making the unit especially easy to install and comes with step-by-step instructions.

The Windmill Air also features an app, so you can turn it on/off remotely, set it to one of three different modes, and use your voice with support for Alexa and Google Assistant. There are two versions of the Windmill Air: a larger 8,300 BTU and a smaller model that hits 6,000 BTU. We prefer the larger model, not only because it can cool a larger space, but because it is the more efficient of the two. While it isn’t all that quiet (54.5 dB), a decent 11.9 CEER rating makes a strong pick.

Best budget: Frigidaire FFRE053WAE

Frigidaire

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Buy it used or refurbished: eBay

Why it made the cut: The Frigidaire FFRE053WAE offers quiet operation, a programmable timer, and impressive energy efficiency at an affordable price.

Specs

  • Type: Window
  • Energy efficiency: 12.1 CEER
  • BTUs: 5,000
  • Energy Star Certified: Yes
  • Estimated noise level: 50 dB (low) – 56 dB (high)

Pros

  • Affordable
  • Programmable timer
  • Quiet operation

Cons

  • Noisy on high

The Frigidaire FFRE053WAE includes everything you need in a basic air conditioner for a small room. It features a programmable timer and remote control. Plus, it’s Energy Star certified and very efficient. The unit is also relatively quiet on low at 50 dB but gets relatively close to our noise limit of 56 on high. And there’s no avoiding the fact that this air conditioner is affordable because it isn’t all that powerful. We don’t recommend going for this one to cool off a big room. If 5,000 BTUs will get the job done, then this is a very strong choice.

FAQs

Q: How much money will an energy-efficient air conditioner save me per year?

According to the Department of Energy, an air conditioner with an Energy Star rating can save you an average of $70 per year compared to older, less efficient air conditioners. That may not sound like a lot, but it adds up over the lifespan of your appliance. With modern air conditioners, you can save even more money by programming your unit to cool on a schedule.

Q: How cool should my space be if it’s 100 degrees outside?

For the most energy efficiency, the U.S. Department of Energy recommends residents set their indoor temperature to 78 degrees when they’re asleep during the summer months. When you go out, you should set the temperature to 85 degrees. When you’re sleeping, a balmy 82 degrees. Of course, these are recommendations for people with central air, who can cool their home to a specific temperature, and don’t keep your personal preferences in mind.

Q: Is it more energy-efficient to leave an air conditioner on all day?

The short answer is yes, it is more energy-efficient to leave your air conditioner on all day. The long answer is a little more complicated. The most effective way to run your air conditioner is to program it to keep your space at a specific temperature throughout the day, whether it’s the suggested 78 degrees or slightly cooler.

Surprisingly, the worst thing you can do is turn the air conditioner off completely. Yes, you save power when it’s off, but it’ll inevitably have to work extra hard to regulate your space’s temperature and humidity when you need it again.

Final thoughts on the best energy-efficient air conditioners

As temperatures begin to rise over the summer months, air conditioning can be the difference between a comfortable summer and a sticky, sweaty one. Picking one of the best energy-efficient air conditioners requires a little planning, but it’ll be worth it when you don’t have to suffer through a heat wave. Whatever style you choose, the energy-efficient options on our list will help keep you cool and save you money.

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