Ultrasonic humidifiers

Ten litres is a floor-standing amount of water, and that is the whole proposition here - Levoit's answer to people who were tired of filling a 6L tank every other day. The 100-hour runtime figure is real at the lowest setting and is the longest in the catalog. Levoit's manual also gives a maximum output of 350 mL an hour, which is 2.2 gallons a day and supports about 550 square feet, close to the 600 on the box; at that rate the ten litres last a little over a day. It is still an ultrasonic, so the white-dust and tank-hygiene arithmetic is unchanged, and a bigger reservoir means more standing water to keep clean rather than less.

Sold on being easy to clean - a wide 3.5-litre tank you can get a whole hand into, which is a bigger deal than it sounds given that the narrow-necked tank is why most cheap humidifiers end up growing something. Pure Enrichment publishes its output as well as its runtime: up to 300 mL an hour, which is 1.9 gallons a day, twelve hours to a tank on high and fifty on low. That supports about 470 square feet, almost exactly the 475 it prints in its copy, though the spec table on the same page says 270. What you give up for the wide mouth is a sensor: there is no humidistat, so it runs at the level you set until it is empty, and in a small closed room that is how windows end up wet.

The cheap one, and honest about being cheap. No humidity sensor, no app, no auto mode - a dial, a 2.5-litre tank, a filter sponge and a top-fill opening. For a small bedroom or a desk that is often exactly enough, and the absence of a sensor means there is nothing to drift out of calibration. It is also, unexpectedly, one of the more truthful boxes here: Levoit publishes 190 mL/h at the top of the dial, which is about 1.2 gallons a day and enough for nearly 300 square feet, more than the 219 its own manual claims. The catch is that Levoit's two runtime numbers describe opposite ends of that dial - 25 hours at the 100 mL/h minimum, 11 at the top. What it cannot do is hold a target: it runs at whatever you set until the tank is empty, which in a small closed room means over-humidifying and a damp window.

The teardrop shape has been on nursery shelves for over a decade and is probably the most recognisable humidifier in America. A gallon of water, twenty-four hours and no filter required, though Crane sells an optional demineralisation filter (HS-1932) that screws into the tank for hard water. Crane is inconsistent about what it covers: 500 sq ft on its own product page and on retail listings, 250 in its manual. The arithmetic supports the smaller figure: a gallon over 24 hours is about 246 square feet.

Honeywell's filter-free line exists because plenty of people would rather buy no consumables than buy the right ones. There is no wick and nothing to replace, which keeps ownership about as cheap as it gets here - and it is an ultrasonic with no demineralisation media, so on hard water the minerals that a wick would have caught end up on the furniture instead. A gallon tank and 24 hours works out to about a gallon a day, near enough to what its 300 sq ft claim needs, making this one of the more honest small ultrasonics on that particular number.

Crane's fix for the original Drop's two real problems - the bottom-fill tank and the neck you could not get a hand into - plus a sound machine and a colour-changing nightlight aimed squarely at nurseries. The top opening is wide enough to reach inside and scrub, which is the single most useful change and the reason to pay $5 more. Three sleep sounds, an aroma tray for vapour pads, and the same one-gallon, twenty-four-hour, no-filter arrangement underneath.

Pure Enrichment is unusually straight about runtime: it publishes a range, ten to twenty-four hours depending on the setting, rather than quoting only the flattering end. That one editorial choice tells you more about the machine than any spec - at the high setting a gallon lasts ten hours, which is what a gallon does. It is otherwise an unremarkable and perfectly competent $60 ultrasonic: no filter required, a mist dial, an optional nightlight, auto shut-off. The 500 sq ft claim holds only at the high setting, ten hours to a tank.

Vicks declines to put a square-foot number on this one, describing it only as a medium-room unit - which, given how the rest of the category behaves, is its own kind of honesty. A 4.5-litre tank running 30 hours works out to just under a gallon a day, the same ballpark as everything else at this price. Dual scent-pad slots, a variable output dial, no filter. The usual ultrasonic caveats apply and the tank neck is narrow enough that cleaning it properly means a bottle brush.

Three washable parts, all stainless steel, all dishwasher safe - that is the entire product thesis and it is aimed squarely at the reason most humidifiers end up in a cupboard. Plastic tanks grow a pink film in the seams and scratch when you scrub them; a steel tank can be boiled, bleached or run through a dishwasher indefinitely. Carepod charges $350 for that, which is four times a Levoit with more capacity. It is still an ultrasonic with no demineralisation media, so hard water still means white dust, and the 500 sq ft Carepod prints is more than its own tank and runtime support: 4 litres over 30 hours is under nine-tenths of a gallon a day, enough for about 210 square feet.

Fifty dollars buys the parts that usually cost more: a 4-litre top-fill tank, a real humidity sensor, app control and a 28 dB low setting. The demineralisation cartridge is the part to read carefully. The HM311S takes one, but the $49.99 listing does not include it - Dreo sells it as an $18.99 three-pack or in a $54.99 bundle - and without it the unit atomises whatever minerals are in the tap water, like any other ultrasonic. On the 300 sq ft Dreo prints, the arithmetic is tight rather than wrong: that room wants about 1.2 gallons a day, which would drain the tank in about 21 hours rather than the 32 advertised.

A litre more tank than the HM311S, from the same playbook: humidity sensor, app, top fill and a 28 dB low setting. Dreo rates it for 300 sq ft, the same room as the smaller unit. That room calls for about 1.2 gallons a day, which would take the 5-litre tank down in roughly 26 hours against the 42 advertised - a modest stretch rather than a wild one. Neither Dreo ships a demineralisation cartridge in the box, and the 512S takes a different one from the 311S, sold as a $25.99 three-pack, so on hard water budget for it from the start. Against the HM311S the extra $20 buys a litre of water and not much else: both have an aroma pad tray, a sensor and the same app.

Sold through West Elm and QVC rather than a hardware aisle, which tells you what it is optimised for - a slim tower in a walnut-and-white finish that looks like a speaker. Despite the "Hybrid" in its name it is a cool-mist ultrasonic with no heater - Objecto's own spec reads "Ultrasonic, Cool Mist" - and while the four mist levels are real, a 2.4-litre tank is the smallest of anything here claiming 650 square feet, and twenty-two hours of runtime from it works out to under 0.7 gallons a day. Holding the room it claims would empty the tank in under six hours. Buy it because you want that object on that table; the arithmetic is not the reason.

Vicks sells more humidifiers through drugstore shelves than most of this catalog sells anywhere, and the VUL545 is the one people pick up at nine in the evening when a child has croup. It works: a gallon of water, visible cool mist, a scent pad slot for menthol, and no filter to have forgotten to buy. What it will not do is hold 400 square feet - that room wants about 1.6 gallons a day, about two and a half times what the advertised 36-hour run delivers - and on hard water it powders dark surfaces within a few days.

Sixty hours of runtime and 505 square feet cannot both be true at once, and the Classic 300S is the clearest illustration of that in the whole catalog. Drain a 6-litre tank over the advertised 60 hours and the unit is putting out about 0.63 gallons a day, which is bedroom-sized. Hold 505 square feet at 40% and it needs roughly 2 gallons a day, which empties that same tank in under 19 hours. Both numbers come off Levoit's own spec sheet; only the setting changes. What you actually get for $80 is a competent, genuinely quiet ultrasonic for one room, with top filling, a real humidity sensor, an auto mode that targets 40-50%, and app control that owners either use constantly or never touch again. It is an ultrasonic with no demineralisation media, so hard tap water becomes white dust on the nightstand, and the tank wants weekly cleaning or it turns pink.

A tower with a 1.47-gallon tank, a demineralisation cartridge in the box, and a 426 sq ft claim - an oddly specific number that at least suggests somebody calculated rather than rounded up to 500. HoMedics now lists it as the Decor Series Large Humidifier, and its box gives the CMTF91 a 17-18 dBA noise figure, which with the cartridge makes it one of the quiet, dust-free units here. Seventy hours on the lowest setting is among the longest here, which as usual means the lowest setting moves very little water: about half a gallon a day. Where it earns its place is the combination of a demineralisation cartridge and a real humidistat at $100, which most rivals at this price do not offer.