Ultrasonic humidifiers

The interesting number is not 6 liters, it is 60 hours. A 1.58-gallon tank that lasts 60 hours on low is moving 0.63 gallons of water a day, and 0.63 gallons a day is what covers about 187 square feet at the rate we derive from Aprilaire's own published sizing. That is a bedroom. It is not the 505 square feet on the specification table.

Both figures are true and they describe different settings. Levoit publishes the endurance of the quietest setting and the ceiling of the loudest, and never the output that connects them, so a buyer has no way to check the coverage claim. That is not a Levoit problem, it is a category problem, and it is the reason every roundup here shows the implied figure beside the claimed one.

What you are actually buying is the absence of a filter. No wick means no 30-to-60-day replacement cycle and no annual filter bill, and it also means every mineral in your tap water leaves the machine as white dust or stays behind as scale. Run low-mineral water or accept the descaling, which the EPA's own humidifier guidance is blunt about.

Skip this ifyour water is hard and you will not commit to distilled. An ultrasonic unit atomizes whatever is dissolved in the tank, and this one has no wick to catch it.

A 10-liter reservoir running 100 hours is 0.62 gallons a day, which is almost exactly the same daily output as the 6-liter Classic 300S. The tower holds more water; it does not move more water. What you are buying is refill interval, and that is a real thing to buy.

For a bedroom, four nights between refills changes the ownership experience more than any spec on the box. It also means four nights of water standing in a tank, which is precisely the condition the EPA warns about. If you take the long refill interval you have to take the cleaning discipline with it.

27.5 watts for a 10-liter unit is efficient, and the sub-28 dB figure is the quietest published number in this set. If a humidifier has ever woken you up, that number is the one to look at.

Skip this ifyou want a machine you can ignore. The long refill interval tempts you to leave water standing, and standing water is exactly what the EPA tells you to empty and dry every day.

Under 26 dB on low cool mist is the kind of figure that decides whether a machine stays in a bedroom, and Levoit publishes both ends of the range rather than just the flattering one. The 41 dB high warm figure is honest and worth knowing before you buy.

0.64 gallons a day implied on low puts this in the same real-world class as the Classic 300S despite a smaller tank: same daily water, fewer hours between refills. If the 300S is too tall for a nightstand, this is the same machine in a shorter body with a heater added.

The 280 W rating is the heater, as it is on the LV600S. On cool mist the draw is a fraction of that. If you never use warm mist you are not paying for it, but you did buy it.

Skip this ifyou want the biggest room this brand covers. The 6-liter LV600S publishes an output figure and a larger claim for similar money.

This is the only unit in the set where you can compute both ends of the range from published figures, because Levoit gives run times for minimum and maximum. 0.66 gallons over 25 hours is 0.63 a day; the same tank over 11 hours is 1.44 a day. At our derived rate that is roughly 188 to 427 square feet, and the honest way to state its coverage is exactly that: a range, with the setting attached.

Notice what Levoit did not do here: it did not put a square-footage number on the box. Given that every other model in its own line carries one that its published figures cannot support, declining to claim one on the smallest unit reads as restraint rather than an omission.

17 watts is the lowest draw in this set by a factor of one and a half, and the flat base with a wide opening is the single design decision that most reliably predicts whether a humidifier gets cleaned.

Skip this ifthe room is larger than a small bedroom. At maximum mist this empties in eleven hours and still only reaches the low four hundreds of square feet.

This is the only unit in the portable group whose maker publishes an output rate, and publishing it is worth crediting. 550 mL an hour is 13.2 liters a day, which is 3.49 gallons a day, which covers roughly 1,030 square feet at our derived rate. That is more than its own 753 sq ft claim, so for once the box is conservative.

The catch is the setting. 3.49 gallons a day on maximum warm mist empties a 6-liter tank in about eleven hours and draws 280 watts while it does it. On the lowest setting the same machine moves 0.76 gallons a day and covers about 224 square feet. One box, a four-and-a-half-fold range, and only the two ends published.

280 watts is the number to think about if you plan to run warm mist all winter. Boiling water is not free, and this is the page where that becomes a real line on a bill rather than a footnote.

Skip this ifyou want to run it flat out overnight and forget it. At the published maximum it needs refilling before morning.