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Window AC unit buying guide: everything you need to know

From voice control to energy efficiency, these are the features to look for in the modern window AC unit.

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Colin West McDonald/CNET

Whether it's an upstairs office that gets stuffy in the summer or your whole apartment that has no central air, a window air conditioning unit can make a hot space livable. And in 2020, retrofit AC units come with all sorts of quality of life features that the appliances of yesteryear never dreamed of.

We've written about buying standard window air conditioners in the past, but what about these smarter models? If you want voice control or scheduling from your smart phone, here's how to find the perfect smart window air conditioner.

Read more: What to look for in a portable air conditioner

A quick breakdown of the basics

Before you think about smarts, you'll want a good handle on what you need from your new AC unit. The most basic question: How well does it cool a room?

Window-unit air conditioners are all rated with British Thermal Units -- usually ranging between 5,000 and 12,000. BTUs are a measure of energy that essentially tells you how effectively a device can lower the temperature in a given space. Generally, you want 20 BTU for every square foot you want to cool (though other factors, such as a vaulted ceiling or shade coverage, can push the final estimate up or down slightly).

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The EPA's Energy Star website provides tools for calculating the necessary BTUs for a given room.

Energy Star

Beyond the basics, here are the other key features you might want to look for: scheduling functions, eco modes and Wi-Fi connection. Each of these elements let you personalize your experience with a window AC unit, whether by setting timers and remotely controlling the device or by tweaking the overall energy usage. 

Finally, some air conditioners are portable, meaning you can wheel them around your house and attach them to different windows as needed. Portable models are generally pricier, they take up floor space and they perform worse than their window counterparts. But if you're not allowed to have window units in your apartment or if your windows simply won't hold a traditional device because of their design, a portable air conditioner might be something to consider.

The second big question: where can you buy a window AC unit? You can usually find air conditioners in stores like Home Depot, Lowes and Walmart. Online, all of those stores -- along with Amazon -- offer fairly extensive catalogues of window units.

If you're interested in a portable air conditioner, check out our full guide on how to buy the best one.

Small rooms

For a small room (meaning 150 square feet or less), a 5,000 BTU model should work nicely. Generally, smaller devices like this tend to have less smarts built in, and that means you can get well-reviewed models, like this $140 GE window unit, relatively cheaply. If you definitely want the smarts, though, don't just buy a higher BTU model without giving it serious thought: Yes, a 12,000 BTU unit will cool down that upstairs office faster than a less powerful unit, but it will do so too quickly to dehumidify the room -- leaving it uncomfortably damp.

If you decide that Wi-Fi features are a must -- even for a super-small room -- consider an 8,000 BTU model, like LG's Window Smart Air Conditioner with Remote. You can run it on a low setting so it doesn't leave your room too humid, and it still has voice control through Alexa and Google Assistant and remote control through a smartphone app.

Medium-size rooms

When it comes to slightly larger rooms -- particularly ones in the range of 340 square feet -- 8,000 BTU window units will be your best bet. These typically run a bit over $200 for bare-bones models like this Window Air Conditioner from Cool Living.

Smart 6,000 BTU air conditioners have actually been around for a number of years, now: we reviewed one of the earlier smart AC units, from Quirky and GE, back in 2014. So if you're looking for something with Wi-Fi connectivity, it's easy to find well-reviewed options like the aforementioned LG Window Smart Air Conditioner with Remote right at the $300 mark. These devices come with extras, like smartphone or voice control from Alexa or Google Assistant, as well as more robust scheduling controls. 

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Smart speakers like Alexa and Google Assistant can help control some newer AC units.

Tyler Lizenby/CNET

Large spaces

If you have a large room or want to cool a small apartment with a single AC unit, you'll need something with a little more power. 12,000-14,000 BTU units can cover square footage between 550 and 800, and they often feature additional features like energy-efficient settings, low-decibel settings and built-in ionizers.

There's a wide price range for high-power air conditioners. If you want a basic cooling unit, you can find one for a bit under $400, like Cool-Living's basic model. On the other hand, devices like LG's $550 Dual Inverter Smart Window Air Conditioner bring not only voice and smart phone control, but also a washable filter, a 43 decibel volume (that's quieter than many refrigerators) and an energy-efficient "eco" setting.

Another option is to look for devices with built-in ionizers, like Frigidaire's 12,000 BTU Cool Connect Smart Window Air Conditioner, which sells for $490. It gives coverage to 550 square feet, and features remote controls through an app. But more interestingly, its built-in ionizer cleans pollen and other impurities from the air. 

Finding the right device for you

The window air conditioners of 2020 are different beasts from the ones you grew up with. They're more efficient, more powerful and smarter. So the big question isn't necessarily which device is best: It's which device is best for you?

If seasonal allergies are a problem for you every spring like they are for me, maybe a built-in ionizer is more important than voice control. But if you're planning to work from home more, given the coronavirus pandemic, maybe scheduling and remote control on your phone is the crucial feature.

So take the time to think about what you want, and let us know in the comments what you look for in a window air conditioner.