The best essential oil diffusers


Ultrasonic diffusers and nebulisers – top picks.


Seventeen diffusers were tested over a four-week period, and the favourite is the Urpower 300ml Aroma Essential Oil Diffuser. It puts out a strong stream of mist, has a larger capacity and smaller footprint than much of the competition, and, while affordable, has a clean design that looks better than others at its price.

About this guide

This guide was written by the Shannon Palus of Wirecutter (New York Times group) and republished by CHOICE. The products are independently selected. This test was conducted in the United States and was originally published on the Wirecutter website. You can read it here in its original version. Photo: Sarah Kobos

Top pick: the best essential oil diffuser

Urpower 300ml aroma essential oil diffuser

The Urpower produces a strong stream of mist, lasts longer between refills, looks better, costs less, and has a smaller footprint than similar competitors.

The Urpower 300ml Aroma Essential Oil Diffuser is a simple white plastic cylinder in a field crowded with funny shapes and (very) faux wood. 

It's one of the least expensive diffusers in this test, working better than models four or five times the price. 

The medium-size tank provides water for seven hours of a strong stream of mist (though you'll need to add more oil during that time for continued scent). 

It lights up in seven colours, offers a timer function, and has LED indicator lights that aren't as distractingly bright as those on much of the competition. 

It's easy to wipe out with a cloth to keep clean.

urpower oil diffusers

Photo: Michael Hession

The Urpower 300ml Aroma Essential Oil Diffuser produces a stronger stream of mist than most diffusers we tested. Its tank size is larger than most others, its price is lower, its footprint is smaller, and it has a clean and simple design, unlike many other units in this test.

Other handy features aren't unique or essential but set the Urpower apart anyway – there's a 3-option shutoff timer, lights that can cycle through seven colours, and LED indicator lights that aren't too bright or annoying. Plus, it's pretty quiet. While you can get an equally strong diffuser with a sleeker appearance for more money, most people will be pleased with the Urpower 300ml.

The 300mL tank is three times the size of those in most other diffusers at the same price, allowing this model to continually produce mist for seven hours – over twice as long as many competitors with smaller tanks. In addition to the ability to run until it's empty (and then automatically shut off), the diffuser has three timer options to run for one, two, or three hours – a common but not universal feature.

urpower oil diffuser

You can set the Urpower 300mL to run for an hour or two, or until it runs out of water. Photo: Michael Hession

The stream of mist from this diffuser is tied for the strongest seen from any unit in the test, both in volume and in plume height. Most units produce mist at a fraction of the rate that this one does. That stream translates to a scent that's more noticeable than much of the competition. It's also just pleasant to look at.

You get seven options for light colours and two brightnesses for each colour, as well as the option of no light. The small yellow-green LED indicator next to the mist button sticks out less than the red and green light on several of the other units.

This model's cylindrical white plastic design was one of the testers' favourites in a field filled with strange shapes and very fake plastic wood, taking up half the footprint of many other models (including some with smaller tanks). It doesn't draw attention to itself, and it's easy to wipe out with a damp cloth between uses, especially compared to units with a second, decorative lid.

The top of the diffuser snaps snugly into the base, so you can pick up or rotate the whole diffuser by the lid. This design also may make it a little harder for kids to open the diffuser and mess with the water, but it also means it's harder for adults.

This diffuser is also one of the most affordable. You'll be hard pressed to find any diffuser that's much less expensive, and you could easily spend three or even five times the price on a unit that's not as effective. Like most ultrasonic diffusers, this one is quiet, though you can hear a small whirring sound if you put your ear really close.

Flaws but not dealbreakers

Testers had the following problem with nearly every ultrasonic diffuser in the test: Since the device has just two buttons, you don't get a simple on/off switch for the mist or for the lights; you have to cycle through every option to shut off either function. On the Urpower 300mL, this design is particularly annoying for the light, since you have so many options. The buttons beep when you press them, and you have to hold down the mist button for a second before the stream of mist begins. Testers found this annoying at first, but it wasn't an issue after they knew the trick.

The Urpower 300mL also makes a beep sound when it shuts off. If you want to fall asleep while using this diffuser and you are a very light sleeper, the noise might be too loud, as it was for this Amazon reviewer.

The lid can be a little tricky to get on and off the base for some people. "The lid fits over the base with water just fine but once you have it on it takes a bit more force than I think it should to try to get the arrows to line up at the bottom," one reviewer writes.

While this diffuser has a neutral design compared to much of the competition, it is noticeably made of plastic. You can find diffusers made of much more attractive materials.

Runner up: larger size, longer runtime

Asakuki 500ml Essential Oil Diffuser

With as strong a stream of mist as the top pick above, this diffuser has a larger tank you won't have to refill as often. 

However, it takes up more space, and the faux-wood look isn't for everyone.

If the 300mL top pick is sold out or you'd like a slightly bigger tank, consider the Asakuki 500mL Essential Oil Diffuser (or the nearly identical Urpower 500ml Aromatherapy Essential Oil Diffuser). 

We recommend whichever you prefer on price or aesthetics, and both have a strong, rich, stream of mist that's on par with that of the top pick. 

Runner up: an equal 500mL option

Urpower 500ml Aromatherapy Essential Oil Diffuser

Nearly identical to the Asakuki, this 500mL diffuser is available in light faux-wood or all-white.

At around double the tank size of the top pick, 500mL diffusers requires fewer refills – and in fact, these diffusers are the only style tested with a unique low-output mode that can run for up to 16 hours. However, a model at this size also takes up more space. 

The Asakuki has a faux-wood base, which some people will find a little tacky. The version from Urpower is available in all-white, though because of the size and shape, it looks a little orb-like. Both light up in seven colours, have a timer similar to the top pick's, and are easy to wipe out between uses.

asakuki oil diffuser

Photo: Sarah Kobos

The Asakuki 500mL Essential Oil Diffuser produces an equally strong stream of mist compared to the top pick, but with a larger tank, it lasts even longer – up to 16 hours on its weakest setting, and around 10 hours on the higher settings. 

It lights up in seven colours and has LED lights that are a bit more subtle than the top pick, and it's just as quiet. However, it takes up more space than our top pick, and the faux-wood base looks, well, pretty faux. 

This model was tested side by side against the Urpower 500mL Aromatherapy Essential Oil Diffuser. The two are nearly identical, so testers recommend whichever you prefer (either based on price or aesthetics). The Urpower model comes in light faux wood, or white, which resembles a large plastic orb that could stand out in a bad way.

A 500mL tank is five times the size of most other diffusers at the same price, and nearly double the size of the top pick. 

Both the Asakuki and Urpower diffusers have three timer options to run for one, two, or three hours. Unlike all the other diffusers in this test, these models have an option to produce a weaker stream of mist for up to 16 hours, making these the only diffusers we recommend that can run continuously all day.

Urpower 500ml oil diffuser

Photo: Sarah Kobos

The Asakuki includes seven options for light colours with two brightnesses each, or you can run the unit with no light at all. The indicator light is weaker than that of the top pick, a plus if you'll be running the diffuser while you sleep. The same goes for the Urpower.

The design of this diffuser isn't the testers' favourite: it's larger and flatter than the top pick, taking up more space and standing out a little more (and not in a good way). The plastic is a bit shinier, too. The Asakuki's faux-wood base is potentially an eyesore, and the Urpower, which is also available in a monochrome style, might not suit everyone's tastes. Either could work at anyone's home as long as they're okay with the bigger footprint – and with a larger tank and longer runtime, a 500mL diffuser could be particularly well-suited to a business (like, say, a yoga studio) where it could run all day on a low setting.

The lid on these diffusers doesn't snap onto the base, making it a good choice if you have trouble gripping or twisting. However, it's less secure than the top pick's lid, which is a concern if you have curious children who want to get a look inside.

Also great: a smaller, stylish option

Vitruvi Stone Diffuser

This compact model is the most attractive recommended diffuser, but its smaller tank doesn't last as long and its stream of mist isn't as powerful as the top pick's. It's also far pricier.

If you'd prefer a diffuser that looks a little nicer and don't need to diffuse scent in a large space, we like the Vitruvi Stone Diffuser. With a porcelain shell in a few neutral colours, it's the only stylish diffuser in the test that both features a strong stream of mist and is easy to use. 

It's one of the only diffusers in the test with a truly subtle indicator light (positioned on the back of the unit), making it the best choice if you'd like it to run while you're sleeping in a dark room. 

The tank is on the small side, so you'll have to refill more often, and while it's easy to wipe out, two layers of lid make cleaning and refilling slightly more annoying than with the top picks above. It's also pricier (but could make a better gift).

vitruvi oil diffuser

Photo: Sarah Kobos

If you want a diffuser that's very good looking, consider the Vitruvi Stone Diffuser. The stream of mist is stronger than that of most other small, stylish diffusers, though not as strong as the top pick's, and the Vitruvi only runs continuously for three hours on a single fill. It has a porcelain shell and comes in white, black, and blush. A small ring around the bottom can light up, for some subtle mood-setting. The LED indicator lights are small and placed on the back of the unit, making this the best choice if you'd like to run the diffuser in a dark space.

At 100mL, the tank is one-third the size of the top pick's, and you'll have to refill it more often if you'd like it to run continuously for more than a few hours. This diffuser has an option for intermittent diffusing, which the top pick lacks; on this setting it can run for seven hours. "I personally don't like this setting as much, as the continuous stream of mist makes for a nicer ambience," says tester Shannon Palus.

vitruvi stone

Photo: Sarah Kobos

There's only one light option on the Vitruvi: a small ring of yellow around the bottom. It's more elegant than the multi-colored light options on the other picks (though perhaps not as fun).

The conical design and stone-like texture of the porcelain shell make this diffuser the most pleasing to look at even when it's not running. The top pick is an appliance; the Vitruvi is more of a small sculpture.

The two lids, one plastic and one stone, are annoying to remove to refill the unit or clean it out. Otherwise, the diffuser is easy to wipe out between uses.

Between the smaller size, the elegant appearance, and the annoyance of the two lids, this diffuser could be a good fit if you don't expect to use it on a daily basis and would prefer something attractive that you could display on a shelf or mantel as a functional complement to your decor.

Also great: the best nebuliser

Organic Aromas Raindrop 2.0 Nebulizing Essential Oil Diffuser

If your top priority is a strong smell, go with a nebuliser. It's pricier than the top pick and harder than ultrasonic models to clean, but unbeatable at filling a room (or a few) with scent.

If you want a device that does the best possible job of dispersing scent to multiple rooms at once and you don't mind spending more money, the Organic Aromas Raindrop 2.0 Nebulizing Essential Oil Diffuser is a nebuliser that mists pure oil, unlike the other picks, which are ultrasonic. (Here's a detailed explanation of the difference.) 

The lights on this diffuser are dim compared with those on the top pick and runner-up, and there's no cool mist to stare at. 

It's less expensive than others of its kind, prettier, and far quieter (nebulisers typically make very loud grinding or buzzing sounds). 

The Raindrop runs for two hours, dispersing oil intermittently, and an automatic shutoff helps avoid overdoing the smell. 

Like all nebulisers, it's annoying to clean.

organic aromas

Photo: Michael Hession

If you want a stronger aroma and are willing to accept a more difficult cleaning process, consider the Organic Aromas Raindrop 2.0 Nebulizing Essential Oil Diffuser. Of the five nebulisers in this test (which were all great at diffusing), the Raindrop 2.0 is by far a favourite for aesthetic reasons. 

On low settings it's just as quiet as an ultrasonic diffuser (most nebulisers are loud). Unlike other nebulisers, it has neither a ton of buttons to mess with nor too few options to control your experience.

This diffuser is strong – capable of dispersing enough scent to fill a whole apartment. It runs intermittently for two hours on about 20 drops of oil. The Raindrop 2.0 disperses oil for two minutes and then turns off for one minute; while some other nebulisers offer the option to customise the length of their puffs, testers didn't find that necessary, since they could still adjust their strength. 

If you want the Raindrop 2.0 to run longer, you have to reset it, but two hours should be long enough to scent a room and have the fragrance last a bit. While other nebulisers can run until you shut them off, testers found them to be noisier and more expensive.

The Raindrop 2.0 has a dial to control the amount of mist that comes out. And while the diffuser does make noise, it's not very loud unless you have it misting on full blast. 

You'll need to clean it about once a week (and between oil if you're using thick oils like sandalwood). That's more cleaning than nebulisers with fewer glass parts would require – and a more difficult overall cleaning process than ultrasonic – but the appearance, price, and low noise levels of the Raindrop 2.0 more than make up for the chore.

organic aromas

The Raindrop 2.0 has a touch-sensitive button to turn the light on and off. Photo: Michael Hession

The Raindrop 2.0 comes with either an opaque black base or a wood base, with a grippy material on the bottom to keep it stable. In tests, the touch-sensitive button to turn the light on and off was too easy to press by mistake when turning the device on, and sometimes it took a couple of taps to turn off. This was annoying, but not a dealbreaker.

The fine mist this diffuser sprays might get on whatever you have sitting nearby, as one Amazon reviewer notes, so make sure to put nothing near it that you can't wipe down.

Who should get an oil diffuser?

7 oil diffusers who should get Listen up, kids: This is not a picture of tiny beverages. Photo: Michael Hession

If you want your place to smell nicer, a diffuser is a solid alternative to candles. Since a diffuser can't catch fire, you can leave it on in one room while you're away or sleeping. Unlike with candles or more passive scent dispensers, you can vary the scent just by choosing a different oil. A diffuser will also make any bath feel a little fancier. 

But diffusers do come with a few annoyances: unlike candles, diffusers take a couple of minutes to set up, and they need cleaning every few uses. And if you have small kids, pets, or respiratory problems, there are reasons to consider skipping a diffuser.

You'll find blog post after blog post – often on sites that had the word wellness in their name – about what essential oils can do for your health. But there's little scientific evidence to back those claims up. You can find a good summary of what researchers do and don't know at Berkeley Wellness, a rare "wellness" site that is edited by an MD, relies on peer-reviewed research, and is associated with UC Berkeley. Diffusers in this guide are recommended only for their ambience, and an essential oil diffuser should never be a replacement for medical care.

For example: Don't pay attention to claims from natural-health proponents that diffusing essential oils can help you breathe easier. In fact, if you have asthma or trouble breathing, be cautious. No studies explicitly look at the effect of using an essential oil diffuser on symptoms of asthma, write experts on the American Academy of Allergy Asthma & Immunology's website. "Anecdotally, there have been reports of respiratory symptoms in asthmatics and non-asthmatics due to a variety of diffused essential oils," the AAAAI experts write.

If you have small children, a diffuser comes with additional considerations. Plan to store your essential oils out of reach, as they smell good enough that kids might assume they are also tasty. Many oil bottles lack childproof caps, and most can be harmful in a high enough dose. Certain oils like wintergreen, camphor, and tea tree can be harmful to small bodies if they ingest as little as a teaspoon, according to Berkeley Wellness. In one case, 4mL of wintergreen proved fatal. And ingesting citrus and cinnamon oil can cause painful irritation, said Nena Bowman, the managing director of the Tennessee Poison Center.

Likewise, if you have pets, keep essential oils out of reach from them, too, and diffuse them with caution. While the biggest danger comes when owners apply oils to their pets (which you should not do at all), you'll want to avoid putting certain oils in the air too. In the post Are Essential Oils Safe for Pets? Wirecutter staff writer and pet owner Kaitlyn Wells lists which specific oils to steer clear of. Experts she spoke to advised against using a diffuser in the same room as a pet, as the oil can settle on their fur. If you have a bird, skip the diffuser altogether: birds' lungs are sensitive.

The competition

Tester Shannon Palus says: "We can name several other diffusers that we'd buy if we preferred their appearance over that of our top picks, or if we really wanted a feature (like intermittent diffusing) that a similar pick lacked." 

(Unless otherwise noted, these are ultrasonic diffusers.)

Of all the diffusers in the test, the 100mL Stadler Form Mia Aroma Diffuser is the most understated and design-conscious, with a matte finish, no mood light, and just one button. Next to the competition, however, it offers a weak stream: this diffuser takes a while to disperse oil, and sometimes it's hard to see the mist at all, which makes it less visually interesting.

The Stadler Form Jasmine is the larger version of the Mia and comes in more colours. It has an option to run in intervals, 10 minutes on and 20 minutes off, for 24 hours. While the mist stream is stronger than the Mia's, it's still weaker than that of the top picks. Also, one Amazon reviewer notes that the LEDs are strong: "Wow the lights are like a lighthouse beacon in the night."

There is a 100mL version of the Urpower Essential Oil Diffuser, another popular model from a manufacturer that leads the space. At that size, you have a lot more design options, and the testers felt they could recommend something more attractive than this model's plastic finish – which led them to the Vitruvi, as well as several other stylish small diffusers that were considered and dismissed.

Testers like that the Now Solutions Real Bamboo Ultrasonic Oil Diffuser is made of real wood. Plus, at the time of writing, Fakespot gives the Amazon reviews a B, uncommon among diffusers. It has an option for intermittent diffusing as well as a timer – a combination that wasn't seen on any other ultrasonic diffuser. However, the stream of mist is weaker than that of the top picks, and it doesn't look as elegant as some of the other diffusers.

The DebonAir Rechargeable Ultrasonic Diffuser in Black is bulky, has two lids that are annoying to take on and off, and has a design that's sleek but that the testers personally didn't find appealing: black plastic with a rose gold accent. If you really like the looks, it might be worth getting, as the stream of mist is decent.

Testers liked the symmetrical shape of the Anjou Essential Oil Diffuser, as well as its large size and unique pyramid design. However, several slightly annoying attributes together disqualified the Anjou early in testing: The water reservoir is shallow, so the device takes up more space on a shelf or nightstand than the other 300mL diffusers; the buttons make a beeping sound when you press them; and the faux-wood finish on the bottom is more likely to clash with decorating schemes.

The InnoGear 200mL Wood Grain Aromatherapy Essential Oil Diffuser has most of the same problems as the Anjou diffuser, including a large footprint and buttons that beep. (In fact, the bases of the two diffusers are nearly identical.) The fill line isn't clearly marked inside, either, and the unit is made of faux-wood plastic.

Though they are slightly different shapes, the InnoGear Aromatherapy Essential Oil Diffuser is functionally identical to former runner-up pick, the 120mL Urpower. But this model costs a little more and has a slightly smaller tank.

Of all the diffusers in this test, the Diffuser World Aroma-Ace, a nebuliser, is the most industrial-looking: no wood (real or fake), no colourful lights. It was also louder than anything else by far, emitting a grinding, buzzing sound as it dispersed oil – it sounded kind of like a refrigerator with a worn-out compressor. (Diffuser World sells a "silencer" attachment that is supposed to dampen the sound, but testers found it didn't work that well.)

The Aroma-Ace does have one of the best timers: you can adjust the amount of time it sprays oil as well as the amount of time it rests (between a few seconds and 20 minutes). As with the other nebulisers, you can adjust the amount of oil it sprays, too. Unlike many nebulisers, the Aroma-Ace comes with two atomisers, so you can switch oils without having to clean the system. The unattractive design also doesn't seem as easy to break as the glass nebulisers.

With the Diffuser World Aroma-Express, another nebuliser, you have no option to diffuse oil intermittently, which testers found to be an important feature for nebulisers. This model is also an industrial-looking device, and in tests it made a grinding noise as it ran. That said, if you're looking for a nebuliser that doesn't include any glass components, the Aroma-Express is effective, and it's less expensive than your other options.

The Diffuser World Aroma-Infinity nebuliser is similar to the Aroma-Express but has an option to diffuse the oils intermittently. The sound it made in tests was higher pitched and softer. However, these features probably aren't worth the price for most people.

And here's the competition we wouldn't buy:

The ceramic-and-wood Homedics Ellia Gather Ultrasonic Aroma Diffuser is stylish and produces a nice stream of mist that is perhaps not as strong as that of the picks above. However, it must be operated with a small remote which was annoying to use and that seems all too easy to lose.

The Muji Ultrasonic Aroma Diffuser from the popular Japanese retailer Muji costs more than the competition yet doesn't offer any clear benefits. Muji's diffusers are similar in design to many of the inexpensive models in this test, though they don't give you the option to change the light to a different colour. After a quick visit to a Muji store to see these in person, Wirecutter testers dismissed them.

The InnoGear 500mL Aromatherapy Essential Oil Diffuser is one of the largest out there, and seems to mimic the design of the large Muji diffuser. It comes at a great price, but testers were skeptical about the positive customer reviews since Fakespot gives them a D grade currently. It also has a very large footprint at 168mm.

The Meco 300mL Aroma Essential Oil Diffuser appears to be identical to the top pick, but Fakespot gives the quality of the reviews an F at this writing, noting, "Our engine has profiled the reviewer patterns and has determined that there is high deception involved." Therefore, Wirecutter didn't test it.

Testers were intrigued by the round, pebble-like shape of the BlueFire Electric Ultrasonic Humidifier Aroma Diffuser, but it was the most difficult to use of everything tested – the only ultrasonic diffuser for which testers had to consult the instruction manual. It has two layers of plastic that you need to remove to fill the water tank, and the buttons are located on the back next to the cord and aren't clearly marked.

The Joly Joy Wood Essential Oil Diffuser is one of the few ultrasonic diffusers made of real wood, but it costs about twice the price of the top pick. Also, currently Fakespot gives a D grade to the Amazon reviews, which are not that great to begin with.

Wirecutter tested the Welledia Pleasant Essential Oil Glass Nebulizing Diffuser with Bamboo Base and Color LEDs because it's one of the nicer-looking nebulisers available. However, the LED can't be turned off, something testers didn't realise until they ordered it. This model was a lot louder than the Raindrop 2.0, making a buzzing noise as it diffused.

Cleaning your diffuser

Manufacturers often recommend cleaning out ultrasonic diffusers once every few days or uses, so that oils don't build up and nothing can grow in the stagnant water. The maintenance instructions for the top pick recommend using a little fragrance-free dish soap. To get it really clean, Essential Oil Haven suggests running it in a well-ventilated space for a few minutes with water and a few drops of white vinegar every so often. If you're switching oils between uses, wipe out the diffuser with a damp cloth.

The maintenance instructions for the Organic Aromas Raindrop nebuliser recommend cleaning the device with rubbing alcohol once a week (or cleaning it immediately after running it with a thick oil like sandalwood). If you're switching oils, clean it between uses. Every once in a while, soak it in hot water with dish detergent to get it really clean.

One more note on the topic of cleanliness: testers used tap water while testing the ultrasonic diffusers, even though many people and some companies suggest using distilled water because the minerals in tap water get propelled into the air along with your oil. The EPA says that it's perfectly safe (PDF) to use tap water in an ultrasonic humidifier (which puts a lot more water into the air than a diffuser). However, tap water can produce a fine, white dust near the device. Testers did not notice this dust during diffuser testing, possibly due to the diffusers' much smaller output than humidifiers.

The research

This guide was written by the editorial staff of Wirecutter (New York Times group) and republished by CHOICE. The products are independently selected. This test was conducted in the United States and was originally published on the Wirecutter website. You can read it here in its original version.

Author Shannon Palus says:

I read and viewed dozens of blog posts, reviews, and YouTube videos to get up to speed on the available kinds of diffusers and brands, and I tested 17 different diffusers and nebulisers. I checked in with John Holecek, a physicist and author of [Wirecutter's] humidifier guide, to understand how airborne oil spreads, as well as with Nena Bowman, a poison-control expert, to discuss the risk of kids getting into your essential-oil stash. Wirecutter staff writer and resident pet expert Kaitlyn Wells spoke to experts about how to diffuse oils if you have furry family members (with caution!).

Author Shannon Palus says:

I spent four weeks using a selection of ultrasonic diffusers and nebulisers around my apartment. We quickly eliminated a few for having undesirable design elements like taking up a lot of space or having buttons that we found impossible to navigate without looking at the manual.

We observed the diffusers running side by side to visually compare the size and height of the streams of mist, the key factors in how well they ought to distribute oils. Then, we ran the diffusers for several hours to confirm whether they effectively made the room smell like essential oils. (Scientifically measuring the exact effectiveness of each diffuser was beyond the scope of our review, but we found observing plume size and taking subjective notes on smell generally gave us a clear picture of which units worked better than others.)

To discover everything that could possibly be annoying about a diffuser design, I rotated them through every location I could think of: kitchen counter, living room next to the litter box, guest room, bookshelf, atop the toilet tank, on a coffee table in my bedroom while I slept. I also used the diffusers at night in a dark room to see how bright the LED indicator lights were.

I paid attention to the noise level from nebulisers. When any nebuliser is on full blast, it produces a buzzing sound. The best ones allow you to turn them down so that this sound becomes nearly inaudible (but that makes the stream of mist weaker, too).

Search for "essential oil diffuser" on Amazon and you'll get pages upon pages of devices that are all slight variations of one another – many with buttons that look identical. The company that makes the top pick even confirmed that some of the manufacturers get their diffuser parts from the same place.

Despite the similarities among models, there are two distinctly different types of diffusers overall: ultrasonic diffusers and nebulisers.

Ultrasonic diffusers are the more popular type in part because they're more affordable and they put out a more subtle scent, using a vibrating diaphragm to turn a solution of water and oil into fine, cool mist. 

Nebulisers, which diffuse concentrated oil by blowing compressed air through it to turn it to mist, produce a stronger smell, and they are less popular perhaps because they usually cost more and can make more noise.

One other thing to note about types: The word "ultrasonic" applies to some humidifiers as well, but oil diffusers are not humidifiers – even though diffuser manufacturers sometimes advertise them as such. If you were to run (and refill) an oil diffuser continuously, it would distribute around 1000mL of water over 24 hours. In contrast, Wirecutter's pick for the best humidifier puts at least its full tank's volume of 3785mL of water in the air over the same amount of time.

There are recommended models in both types of oil diffuser, but the majority of picks are ultrasonic, and the features you typically see on ultrasonic models guided the selection criteria. Here are the factors that set the best models apart, in order of importance:

  • Tank size: The size of the tank, more than any other detail, determines how you'll interact with the diffuser. Ultrasonic diffuser tank sizes range from 100 to 500 millilitres; the best diffusers balance the benefits of a bigger size with a small footprint. Generally, larger tanks mean thicker mist and longer runtimes without needing refills. A larger tank tends to work a bit better for a larger space.
  • Power: Regardless of tank size, testers wanted to see a strong stream of mist. They've observed that impacts how effective the diffuser will be overall and how interesting it will be to look at (a piddly stream of mist isn't very exciting).
  • Material: This is a displayed object, so aesthetics matter. Most people will opt for the common semi-translucent white plastic design, but you can find oil diffusers in other materials, like ceramic, porcelain, fake wood, or even real wood. Generally, better materials tend to appear on pricier, smaller models.
  • Lids: The easiest to use (and clean) diffusers have just one lid. Fancier diffusers made from materials other than plastic often have two layers of lids – one functional and one decorative. This can be annoying to clean but it's not a dealbreaker, especially if your diffuser is going to be more of a set piece on a mantel for occasional mood-setting than a product in constant use.
  • Timer: Many medium and large diffusers have a timer that will turn off the diffuser after one or a few hours. This function allows you to run the diffuser several times without refilling the water. (You should empty and wipe out your diffuser every few days if you're not using up all the water.) It's a nice feature but not necessary.
  • Intermittent diffusing: It's nice when there's an option for the diffuser to mist or spray oil for a set amount of time and then rest, diffusing intermittently; this pattern keeps the diffuser going longer on a single fill.
  • Lights: Most ultrasonic diffusers light up in some fashion or another, often in a rainbow of colours. The colours can be relaxing or a little cheesy, depending on your tastes. Luckily, they can almost always be turned off.

With these criteria in mind, testers shopped among hundreds of oil diffusers for sale at Amazon, Target, and Bed Bath and Beyond (in the United States) and they also looked at niche retailers like Sephora, Madewell, and Anthropologie. They eliminated dozens of diffusers that didn't meet the criteria and eliminated a few more (with glowing Amazon reviews) after running the URL through Fakespot, crossing off any with a Fakespot rating below a C. This left them with 13 diffusers to try firsthand in the first round of testing. For an update, they tested four additional diffusers, this time prioritising diffusers that look nice.

  1. Amanda Z. Naprawa, Essential Oils: What You Should Know, Berkeley Wellness, March 1, 2016
  2. John Holecek, Tim Heffernan, The Best Humidifier, Wirecutter, November 28, 2016
  3. How to Clean Your Essential Oil Diffuser, Essential Oil Haven
  4. Weekly Five, Essential oil diffuser review, YouTube, August 4, 2015
  5. Diana Balekian MD, Aidan Long MD, Dennis K. Ledford, MD, FAAAAI, Essential oil diffusers and asthma, American Academy of Allergy Asthma & Immunology, December 1, 2015
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