By Sabrina Imbler and Kit Dillon
After 25 hours of research, we found that the Bionaire Twin Reversible Airflow Window Fan is the most powerful and user-friendly of five fans we tested—and in mild, dry weather, it can be one of the most affordable, efficient ways to circulate air and make your home more comfortable. This strong, versatile, dual-blade fan clobbered every other window fan we tested in every aspect besides noise.
Our pick: Bionaire Twin Reversible Airflow Window Fan
The Bionaire Twin Reversible Airflow Window Fan was clearly the most powerful fan we tried, with robust breezes we felt from 24 feet away, 8 feet farther than from our runner-up, the Genesis Twin Window Fan. It’s also the easiest to control, with a straightforward interface and an individual button corresponding to the fan’s every feature, including speed, temperature, and electronic reversibility—that means, like many good window fans, you can push a button (rather than physically flipping it) to change from drawing in fresh outdoor air to venting stale or smelly indoor air. The Bionaire is also one of the best-reviewed fans we encountered, and its five-year warranty is longer than that of any other fan we tested. Formerly an upgrade pick in this guide (and a model that several Wirecutter editors have used happily for years), the Bionaire is the most expensive window fan we tested, but only by about $10 over our runner-up, the Genesis Twin. It’s also slightly louder on its highest speeds—but the price and sound are slight compromises we consider worth it for such superior performance.
Runner-up: Genesis Twin Window Fan
The Genesis Twin Window Fan (occasionally listed as the Avalon Twin Window Fan) was the second most powerful fan in our testing, but we recommend it only if you absolutely can’t get the Bionaire. Its airflow is weaker—we felt its wind at a max distance of 16 feet—and its less intuitive controls make accessing basic functions unnecessarily confusing. But leaving the Bionaire aside, the Genesis stands apart from a field of worse competitors—it’s still among the most powerful models available, it’s electronically reversible, and it’s easy enough to install, and one nice side effect of its weaker power is that the Genesis isn’t as loud as the Bionaire. The Genesis is a popular model with a higher proportion of positive reviews than are typical in this category, and it has a one-year limited warranty, though the manufacturer has less of an established reputation for reliable customer support than the maker of our top pick.
Why you should trust us
In researching this guide, and our guide to the best fan, we’ve spent more than 50 hours researching, testing, and living with fans to understand what it takes to move air effectively throughout a room. For the 2018 update, we interviewed several researchers who have devoted their entire careers to understanding how to most effectively cool spaces, including: Danny Parker, a principal research scientist at the Florida Solar Energy Center; Paul Raftery, PhD, a researcher at UC Berkeley’s Center for the Built Environment; and Edward Arens, PhD, the director of UC Berkeley’s Center for Environmental Design Research.
Sabrina Imbler, who wrote the 2018 update to this guide, lives in a muggy Brooklyn apartment without a range hood, and Kit Dillon, the original writer of this guide, grew up in an apartment in New York City that exclusively relied on window fans to keep cool.
Who should get a window fan
Who should get a window fan is closely tied to what window fans do. Unlike ceiling and room fans, which simply circulate indoor air, window fans are designed to draw fresh outside air into your home, or—by reversing the fan direction—to pull stale inside air out of it. Essentially, they improve your home’s air exchange with the outside world. And they do so without taking up any indoor space.
If you live in an area with moderate summer temperatures, or in a dry area with hot days and cool nights, a window fan can help keep your space comfortable at a fraction of the cost of an air conditioner by drawing cooler outside air into your sun-heated home. They’re especially useful if the room you’re ventilating is on the shady side of the building (the north side, in the northern hemisphere), because the outside air there is naturally cooler than the ambient temperature.
If you don’t own a range hood or another way to ventilate your kitchen, a window fan can improve your air quality by drawing smoky/spicy/smelly air out of your home. The same goes for if you work with any kind of volatile compounds, from furniture polish to paint, or even if you paint your nails frequently.
Most window fans, including our picks, actually incorporate a pair of fans, and let you switch the airflow from drawing in to blowing out with the push of a button. But most (including our picks) have a third setting that lets you do both things at once: one fan drawing in air, the other blowing it out. It sounds like the best of both worlds, but according to our experts, it’s actually the worst of both: what gets blown out gets drawn back in immediately, and vice versa. So skip that function.
Finally, know that window fans are especially effective when used in pairs in two different windows: one to draw cool outside air in from the shady side of your home, and another to push hot indoor air out on the sunny side. As Danny Parker of the Florida Solar Energy Center explained, this setup creates a continuous, full-house cross-breeze.
Now for what window fans don’t do. Most important, they don’t mechanically cool the air inside a room, and they don’t reduce humidity, so if you live in an area with hot, muggy summers, they’re not going to help you much. By contrast, air conditioners physically remove heat and moisture to lower the actual and perceived temperature of a room, and in a hot environment there’s no substitute. If you have one room that always seems to be hot, either install a window AC there (here are the models we recommend), or, if the rest of your home already has effective AC, use a room fan (again, we have picks) to blow cool air into it. And also look into ways to minimize the amount of heat the room absorbs from the sun, like cellular window shades, weather-stripping, and other passive methods laid out in our guide to keeping homes cool.
How we picked
We started by compiling an exhaustive list of all of the window fans for sale at major retailers such as Amazon, Home Depot, Walmart, and Lowe’s. We didn’t come across too many promising new models that we hadn’t tested in prior updates—the window fan market is not exactly rife with innovation—but we reevaluated many fans we’ve tested long-term (or tested and dismissed in the past) to see if any deserved a second look. We also pored over customer reviews of these fans, keeping an eye out for any patterns of inconvenience or failure or time-tested durability. Keeping with previous years, we focused this guide on twin-blade window fans designed to be used in standard-sized rooms, and excluding single-fan models that most people would find too loud, too large, and excessively powerful.
With all of this in mind, we developed the following selection criteria:
• Electrically reversible: Some fans require you to physically remove the fan, turn it around, and reinstall it to change the direction of the airflow. That’s an automatic no. An electrically reversible fan can do that with the push of a button.
• Strong airflow: Though you don’t want a gale in your living room, a good window fan should easily move air at least 15 feet away.
• Minimal noise: On its highest setting, the fan should not be disruptively loud, and on its lowest setting, it should create a soft and steady hum.
• Intuitive controls: You should be able to adjust the speed and turn the fan on or off without much hassle. A dimmer for the display is a plus.
• Two-fan design: In our research and testing, we found that models with two internal fans struck the best balance of power and size for most windows. We found single-fan models too powerful and too bulky, and the slimmer three-fan models too weak.
• Multiple speeds: The fan should have at least three speed settings, to produce everything from a gentle zephyr or a full-on gust.
• Longevity: No window fan is built to last forever, but all are a burden to replace, especially if they break during the summer, when models can disappear from the shelves. We preferred fans with an extensive positive track record from owners, and a warranty of three or more years.
• Easy to clean: Though scouring all of the corners of a window fan grate is never going to be fun, it shouldn’t be too difficult to wipe down the fan’s components as they inevitably accumulate dust and grime.
• A good seal: A fan and its extenders should fit tightly in any window frame, sealing out bugs.
• Remote control: Not a requirement, but it’s nice to have a remote so that you can adjust the fan from your bed or desk.
Most fans have an internal thermostat, which should theoretically turn your fan on and off when your room reaches a certain temperature. But in our years of testing, we’ve never encountered one precise enough to work, so we didn’t prioritize this feature in making our picks.
Likewise, most fans let you run one blade on “drawing air in” and the other on “pulling air out.” Our experts said this effectively cancels out a fan’s effects, because the blades are so close together that the one immediately feeds the other. We didn’t consider this feature important.
How we tested
We tested five window fans during an unconscionably humid week in a New York apartment in August 2018. We installed each fan in a standard double-hung window, taking careful notes on how easy they were to set up, and ran them for hours, day and night.
We placed a great deal of value on each window fan’s overall raw power, because unlike room fans, which can be more powerful than most people want, window fans are significantly less effective on lower settings. To test each fan’s airflow velocity, we put each on its highest setting and used the movement of a generic store receipt to measure the effective distance of the breeze the fan created. We also evaluated the usability of each fan’s controls, noting whether the power, temperature, and reverse-flow controls were clearly marked and easy to operate, or clunky and confusing.
We used the iPhone noise meter app Decibel X to calculate the amount of noise emitted from each fan on each power setting, though no one fan sounded significantly louder than any other. Because decibel readings don’t perfectly correlate to perceived sound, we buttressed these measurements with notes on how pleasant (or annoying) we found each fan’s whir. We did not take measurements of the accuracy of how each degree option of the window fan’s thermostat matched the temperature of the room, as we found the feature rarely worked well in any fan.
And as always, we pored through avalanches of customer reviews of the fans we tested, scanning for any red flags regarding the fans’ long-term performance and accounts of dealing with warranties.
Our pick: Bionaire Twin Reversible Airflow Window Fan
For the third year running, the Bionaire Twin Reversible Airflow Window Fan bested every single other window fan we tested. It’s not just more powerful, with its air reaching 8 feet farther than any other fan’s, it’s also easier to install and use. Its seven buttons let you independently set fan speed, air flow (in/out/exchange), thermostat (in individual degrees, versus 5-degree jumps on competitors), and auto/manual operation (not an option on the competition). And it comes with a handy remote control. The Bionaire also has the longest warranty of any window fan we tested from another company: a five-year warranty (covering defects in material and workmanship) that outlasts both the Holmes Dual Blade’s three-year warranty or the Genesis’s paltry one-year warranty. On its highest setting, the Bionaire is slightly louder than some physically similar competitors, but that’s a small dent in what is otherwise the Ferrari of window fans—and you can’t get power without a little vroom.
At its highest setting, the Bionaire is considerably more powerful than every other fan we tested. The company does not publish technical details about many of its products (such as the airflow of its fans in CFM). But in our test, this model made a store receipt flutter from 24 feet away, versus 16 feet for our runner-up, the Genesis, and just 13 feet for a popular and well-reviewed competitor, the Holmes Dual Blade. Like most other fans we tested, the Bionaire has three speed settings, which means that you can adjust it to your preference for power and/or noise—that stood out against the popular Holmes Dual Blade, which has only two speed settings that left us lusting after a middle ground between the barely there whir of low and the windy jet of high.
Installing the Bionaire was quite easy. The fan measures 24¼ by 12 inches without the extension and 30 by 12 inches fully extended, with an extendable locking wing on one side. (The dimensions quoted on the product spec sheet claim 13 inches in height—the actual clearance size needed to install it in a window is 12 inches; we think the discrepancy may be the manufacturer taking a measurement across a bulge across the front of the unit, which adds an inch, but doesn’t affect overall height.) To size the wing to your window, just unlock the two clasps on either side and stretch it out like an accordion until it seals the gap in your window, and then lock it again. If your window is unusually wide, the Bionaire also comes with two 3-inch extenders, which can increase the fan’s width to 37 inches when inserted. The installation instructions are lucid and comprehensive, and include specific advice for properly installing the fan in windows of different widths. In comparison, the instructions for the Holmes, Genesis, and 9-inch window fan models included only notes on the different installation for slider and double-hung windows, without any mention of width.
Once the fan is installed, it’s also exceptionally easy to use—far easier than any other fan we tested. It has a button that powers the fan on and off and adjusts the power level between low, medium, and high. Separate buttons control each of the following features: the fan’s auto/manual setting, the temperature of the thermostat, the airflow reversibility, and even the brightness of the LED screen that displays the temperature—so you can dim it (though not shut it off) at night when you’re trying to sleep. This may seem like the minimum a fan should offer, but during testing we found ourselves increasingly frustrated by fans that had less nimble controls (like the Genesis: no power button, no auto/manual option, and temperature control that overrode the fan speed, locking it on high). Even worse was the Holmes’s all-in-one control button, which requires you to cycle through every possible setting in order to reach the one you want.
At the time of testing, the Bionaire had the most positive owner reviews of any fan on any shopping platform, hands down. We tried to read every review that came from a longtime owner of this model, and most had good things to say.
Many of these customer reviews attest to the fan’s performance over the years. As Amazon customer Rockershipjack writes, “I bought this product 3 years ago. It works great. It runs everyday of the year, many days all 24 hours. I take it apart completely every 6 to 8 months and clean and lube it.” You could also call it a staff favorite. Former Wirecutter editor-in-chief Jacqui Cheng used one in Chicago for three or four years and was impressed by the power of the fan. “I bought this fan to help keep my bedroom cool in the spring/fall without having to turn on AC and that thing seriously moves a lot of air for its size,” she said. Wirecutter managing editor Ganda Suthivarakom has also owned one for several years, and in her previous apartment, used both airflows regularly. “At night, when outside temps are cool here in southern California, the fan could cool down my living room in five minutes.”
The Bionaire comes with a remote that makes it easy to adjust the controls from across the room. The remote worked well for us, and is a handy feature when you want to adjust the fan without getting up. But, more important, the fan is just as easy to use without the remote, thanks to that great control panel—so if you misplace or lose the remote, the fan is still fully functional.
Finally, this model has the most finely adjustable internal thermostat of any fan we tested, letting you pick any target temperature between 60 and 80 degrees Fahrenheit. In comparison, the thermostats on the Holmes and Genesis fans allow you to set it only to numbers at intervals of 5 between 60 and 80 degrees (for instance, 60, 65, 70, 75, and 80) This said, we found all of the tested fans’ thermostats too imprecise to be very helpful—the fans simply ran uninterrupted no matter what target temp we set. Ease of setting fan speed and direction proved much more useful, and on those factors, the Bionaire excelled.
Flaws but not dealbreakers
For a window fan, the Bionaire isn’t cheap. It costs over $60, nearly twice as much as some of the window fans we tested, such as the Holmes Dual Blade or the 65-Watt 9-inch. But we think the fan’s power and proven longevity more than compensate for this higher-than-average price. No window fan is as expensive as an air conditioner to buy or operate, and if you’re in a climate where either option could work, investing just a little more in the Bionaire will give you a solution that’s more powerful and easier to use than any other window fan available.
Some Bionaire owners have complained about the noticeable noise level of the fan. In our testing, the Bionaire emitted 83 decibels while running on high from a distance of 1 meter away, around 13 decibels higher than any other fan we tested. From a distance of 2 meters, however, the Bionaire registered around 65 decibels while running on high, close to the Genesis’s 64.5 decibels and the Holmes’s 61 decibels. In short, as long as you’re not sitting (or sleeping) right next to it, the Bionaire is hardly louder than any other fan. And if noise becomes an issue, running it on medium or low eliminates the distracting whir.
Runner-up: Genesis Twin Window Fan
We’ll be frank: We call the Genesis Twin Window Fan our runner-up, but in fact it ran a distant second place. If you want a window fan, we highly recommend you buy the Bionaire—the absolute best model we tested. But if the Bionaire sells out, or if you absolutely must spend a little less, the Genesis is the best of the disappointing rest.
Like the Bionaire, the Genesis has three speeds, better than the Holmes’s two. Set to high, the Genesis was the second most powerful fan in our testing, moving a receipt from 16 feet away—but that’s weak compared with the Bionaire’s 24-foot reach. Still, the Genesis stands apart from a field of even worse competitors—it’s among the most powerful window fans available, outperforming the popular Holmes Dual Blade. Plus, the fact that it’s electronically reversible distinguishes it from the absolute cheapest fans we considered.
We installed the Genesis easily, despite an instruction sheet with images so pixelated that they looked like photos taken by a UFO conspiracy theorist. But the text itself was sensible enough and included notes for installing the fan in different types of windows, such as double-hung and vertical slider-type windows. The Genesis has two lockable, extendable wings to fit itself inside a frame, and each wing was easy to expand and retract. Unlike the Bionaire’s manual, the Genesis’s included no special directions for installing the fan in windows of varying widths.
We found the Genesis’s interface to be far clumsier than the Bionaire’s. It lacks a separate on/off button. Instead, you turn it on by pressing the speed button and turn it off by holding the same button down. The speed button also cycles through the fan’s three speeds, as expected. But, annoyingly and inexplicably, using the thermostat overrides the speed button and locks the fan on high. We much prefer the Bionaire’s separate fan-speed and thermostat controls. The thermostat button also lets you set the target temperature in only 5-degree increments from 60 °F to 80 °F, versus the Bionaire’s single-degree adjustment. (Again, we didn’t find any of our test fans’ thermostats very useful, but we prefer the Bionaire’s greater range of settings.) At the bottom of the fan, two separate switches allow you to electronically reverse the flow of each fan. We would have preferred a single toggle button that controls the fan’s reversibility, as is the case with the Bionaire.
When we first reviewed this fan, it was branded as Genesis, however it’s occasionally listed as the Avalon Twin Window fan on Amazon, and product pages for some other Genesis-branded products give Avalon as the manufacturer’s name. This sort of ambiguity isn’t uncommon for products these days, though we could find very little information on the company. And although we couldn’t find any worrying trends of failure or breakage within the limited Amazon reviews, the fan has a one-year limited warranty, versus the Bionaire’s five-year warranty. All this considered, we feel the safer buy is to go with a known quantity like the Bionaire.
The Genesis’s one advantage over the Bionaire is that it’s quieter on its highest setting. In our testing, the Genesis made considerably less noise at a distance of 1 meter, measuring 70 decibels versus 83. However, when both fans were set to low and measured at a more reasonable 2 meters, the Genesis was louder at 62 decibels, versus the Bionaire’s 58. In short, unless your fan will be installed right above your bed or desk, we don’t see much advantage to the Genesis—and certainly not enough difference to overcome the Bionaire’s superior controls, instructions, and warranty.
We found the Holmes Dual Blade Twin Window Fan with Comfort Control Thermostat fan needlessly cumbersome to use. The fan has only one button, labeled “mode,” that controls both the speed and temperature and turns the fan on and off. This design means that you must press that lone, loathsome button to cycle through both speeds for each of the five temperatures listed in the thermostat. As Amazon reviewer Brad Waller writes, “If you miss and go one too far, get ready to push push push until you get the right setting.” This irritating feature, along with the fan’s weak airflow and two speed settings, made dismissing the Dual Blade easy. However, if the Bionaire and Genesis are both sold out, the Holmes works just fine and comes with a three-year warranty.
After our prior top pick, the Pelonis 9-Inch Twin Window Fan, was discontinued, we tested a very similar replacement from Home Depot, the 65-Watt 9 in. White Reversible Twin Window Fan. This brandless fan did not have a particularly powerful airflow, moving only as much air as the Holmes Dual Blade (13 feet versus 24 feet for the Bionaire and 16 feet for the Genesis in our “receipt test”). And one of the knobs fell off when we tried to turn it.
If your available window height is limited, or your window slides horizontally, the Bionaire Compact Window Fan is for you. Its 8-inch vertical height is 5 inches shorter than our top pick, meaning that it takes up less room in the vertically opening single- and double-hung windows most common in US homes, and its long, thin shape means that you can also install it in sliding windows (which open and close sideways). However, its lack of a reverse-airflow switch and mixed owner reviews removed it from the running for our top pick.
Earlier tests before the 2018 update
The Comfort Zone 3 Speed Dual Window Fan and Lasko Electrically Reversible Twin Window Fan rival the Bionaire in features, but both models have disappointingly mixed reviews. Though alluringly inexpensive, the Holmes Twin Window Fan with Reversible Air Flow Control pierced our ears with its shrill motors and tested our patience with is barely there breeze. Finally, the Optimus 8-inch Reversible Twin Window Fan does not have enough customer reviews to speak to its longevity and performance, plus it’s too expensive for its limited set of features.
1. Danny Parker, principal research scientist at the Florida Solar Energy Center, phone interview, August 2, 2018
2. Paul Raftery, researcher at UC Berkeley’s Center for the Built Environment, phone interview, August 2, 2018
3. Edward Arens, director of UC Berkeley’s Center for Environmental Design Research, email interview, July 31, 2018
4. Chris Galas, senior product manager at Jarden Consumer Solution, phone interview, August 7, 2018
5. Steven Fox, The Do’s and Don’ts of Window Fans, Bob Vila
Patrick Allan, Keep Your Room Cool at Night by Facing Your Fan Out, Not In, Lifehacker, July 24, 2014
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