What this category is about
Equipment is where most of the money in this subject gets spent and where most of it gets wasted. Not because the machines are bad, but because they get bought for problems they cannot solve: a dehumidifier against a leak, a bathroom fan too weak for the room, a whole-house system installed in a climate where a $20 dryer vent kit would have done more.
Every capacity figure on this site is quoted under the DOE 2019 test method, which moved the test condition from 80 °F to 65 °F. Nothing about the hardware changed in 2019; the number on the box dropped by roughly a third. A machine sold as 70 pints in 2018 is the same machine as a 50 pint unit today, and comparing across that boundary is the single most common sizing mistake.
These articles cover what the ratings mean, what the running costs really are at current electricity prices, and how to tell whether the thing you bought is doing anything.
The four things it keeps coming back to
Sizing by room, not by headline
Capacity should follow floor area and how wet the space actually is. A 500 sq ft damp room needs about 20 pints a day; a 1,500 sq ft space with visible beading needs about 50. Buying beyond that buys you a bigger fan noise, not a drier room.
CFM, and the timer that matters more
Exhaust fans are rated in cubic feet per minute, and the right figure follows the room volume and the number of air changes per hour you want. But the run-on timer — the fan continuing for fifteen minutes after the light goes off — removes more water over a year than the difference between an 80 and a 110 CFM unit.
What it costs to run, honestly
A 30-pint compressor unit draws roughly 300 to 500 watts. Run eight to twelve hours a day it lands somewhere around $15 to $40 a month depending on your tariff. That is a real number worth putting beside the cost of fixing the moisture source instead.
Compressor, desiccant, or neither
Compressor units stall below about 65 °F as the coil ices rather than drains. Desiccant units keep working down to near freezing and put more heat into the room, which in an unheated garage is a feature rather than a fault. In a warm living space the compressor wins on efficiency every time.
Articles
Why modern dehumidifiers are rated for fewer pints
The machines did not get weaker. In 2019 the test moved from 80 °F to 65 °F, and the labels got honest.
What a dehumidifier actually costs to run
Three numbers decide it, and one of them is a setting you control. Most people are paying for the 5% they did not need.
Common questions
Is it cheaper to run a dehumidifier or to ventilate and heat?
It depends on the outdoor air. In cold, dry weather ventilating is cheaper, because the incoming air carries almost no water and you are only paying to warm it. In warm, humid weather ventilating brings water in, and the dehumidifier is both cheaper and the only thing that works. The switch-over point is where the outdoor dew point rises above your indoor dew point.
Do I need a whole-house system or will portable units do?
Portable units are the right answer when one or two rooms fail and the rest of the house is fine, which describes most homes. A whole-house or ducted system earns its cost when the entire building runs humid for months at a time — a humid-climate home in summer, or a house whose basement conditions the air for every floor above it.
Why does my dehumidifier fill the tank quickly at first and then slow down?
Because it is working. The first days pull water out of the air and then out of everything porous in the room — plaster, timber, carpet, stored paper. Once those have given up their moisture the machine is only handling what the room produces each day, so the tank fills far more slowly. A slowing tank is the sign of success, not of a failing machine.