Whole house humidifier sizing chart

This is the reference point for the whole site. Aprilaire is the only maker in our set that publishes a capacity in gallons per day and a coverage in square feet together, and cites the residential sizing standard as the basis for pairing them. Three of its models do it consistently: 12 gal/day to 3,600 sq ft, 17 to 5,000, and 18 to 5,300. Those three pairs are where our 296 square feet per gallon per day comes from.

Everything else follows from the fact that it drains. There is no reservoir, so there is no standing water, so the pink film and the mold that dominate portable-humidifier ownership simply do not arise. The Water Panel goes once or twice a heating season instead of a wick every 30 to 60 days, which changes the recurring cost by an order of magnitude.

The honest counterweight is that this is not a purchase, it is a project. It mounts in ductwork, it needs a water line and a drain, it needs a humidistat and an outdoor sensor, and unless you are comfortable cutting into a plenum it needs a contractor. Our whole-house cost page works through the break-even against running several portables.

Skip this ifyou rent, or you heat with anything other than a ducted forced-air system. Neither is a fixable objection.

Six gallons over 72 hours is two gallons a day, which covers about 590 square feet. The box says 3,000. To actually hold humidity across 3,000 square feet this unit would need to move a little over ten gallons a day, and at that rate its six-gallon reservoir would run dry in about fourteen hours. Both numbers describe the machine; only one describes it at a time, and the maker publishes no figure that reconciles them.

Dry Mode is the genuinely good idea here and it deserves credit. A wet wick sitting in a warm room is the substrate for everything the EPA warns about, and a fan cycle that dries the wicks between runs attacks that problem directly rather than adding an antimicrobial coating and hoping. It also extends wick life, which is the recurring cost.

Thirty watts to move two gallons a day is efficient, and mist-free operation means the minerals stay in the wicks rather than settling on your furniture. If you can live with a coverage claim you should mentally divide by five, this is a well-made machine.

Skip this ifyou bought it for the 3,000 sq ft number. Size it at around 600 square feet on the setting whose run time Levoit actually publishes.

Two published figures that describe opposite ends of the machine, and none of the numbers that would join them up. A 2.5-gallon tank lasting 36 hours is about 1.67 gallons a day, or roughly 493 square feet at our derived rate. Covering the claimed 2,600 square feet would take about 8.8 gallons a day, at which rate the same tank empties in under seven hours.

Both can be true at once: 36 hours is AIRCARE's maximum run time, which will be the lowest of the three fan speeds, and 2,600 square feet will be the highest. It can certainly move more than 1.67 gallons a day on a higher speed. AIRCARE does not say how much more, so its own published data supports sizing it as a large room, not a whole floor.

What it has that most units in our set do not is an adjustable humidistat with digital controls, stated on AIRCARE's own page. On an evaporative machine, which already slows down as the air approaches saturation, that is a second brake against overshooting - and the MAF2 SuperWick keeps your tap water's minerals out of the air.

Skip this ifyou want to humidify a whole floor on the strength of the box. Its own tank and run time support a large room, not 2,600 square feet.

Run the check that fails everywhere else on this page and it passes here. Four gallons a day at 296 square feet per gallon per day is about 1,180 square feet of coverage, against a claim of 1,000. Vornado left itself margin instead of taking it.

It passes because it is evaporative. A wick and a fan can only put as much water into the air as the air will accept, which is why an evaporative unit self-limits near 50% relative humidity and why it cannot produce white dust: the minerals stay in the wick. The EPA's guidance to use low-mineral water exists mainly because ultrasonic and impeller units disperse what is dissolved in the tank, and this design does not.

The cost of that is the wick. Two of them, on a schedule Vornado does not publish, which is the recurring bill an ultrasonic unit does not have. Whether that trade is worth it is arithmetic, and it is worked through in full on our filter-cost page.

Skip this ifyou want silence. Every evaporative unit is a fan, and Vornado publishes no noise figure for this one.