A dehumidifier is one of the few appliances that runs for months without anyone thinking about it, which makes its running cost easy to underestimate and easy to reduce.
The arithmetic is short: watts, multiplied by hours per day, divided by 1,000, multiplied by your rate per kilowatt-hour.
The numbers
Typical draws: a 20-pint unit around 250 W, a 30-pint around 400 W, a 50-pint around 600 W. US residential electricity averages roughly 16 cents per kWh, though it ranges from about 11 cents in parts of the Midwest to well over 30 in Hawaii and California.
At 16 cents and eight hours of actual running per day, that is about $10 a month for a 20-pint unit, $15 for a 30-pint and $23 for a 50-pint. Push the run time to twelve hours and those become roughly $14, $23 and $35.
Note that "hours per day" means hours the compressor is actually running, not hours the machine is plugged in. On a humidistat in a reasonably dry month it might be two; in a wet basement in August it might be twenty.
Where the money actually goes
The setting matters more than the capacity. Every 5% you lower the target increases run time noticeably, because the machine has to work against a smaller and smaller moisture gradient. Going from 50% to 40% can double the hours in a marginal month, and it buys you nothing — mold and dust mites are already suppressed at 50%.
Sizing matters in the opposite direction to intuition. An oversized unit reaches its target and idles; an undersized one runs continuously and never gets there. Idling costs less than running flat out, so rounding up is the cheaper mistake as well as the more effective one.
And a machine fighting a moisture source you could remove is the most expensive configuration of all. Two loads of laundry dried indoors is 64 to 128 ounces a day the dehumidifier has to undo — a meaningful share of a 30-pint unit's entire daily output, paid for in electricity.
Cutting the bill without buying anything
Set it to 50% rather than 45 or 40. Run it on the humidistat rather than continuously. Close the room while it works, or you are dehumidifying the rest of the house through an open door.
Then remove what you can at the source: vent the dryer outdoors, dry laundry outside, run the bathroom fan for twenty minutes after showers. Those changes are free and they come straight off the run time.
One more, specific to cold spaces: if the room drops below 65 °F, a compressor unit ices up and spends its cycles defrosting rather than collecting water. You are then paying full power for a fraction of the output, and the answer is a desiccant model rather than a longer schedule.
The takeaway. Watts × hours ÷ 1,000 × your rate. Then cut the hours: target 50%, size up rather than down, and remove the moisture sources the machine would otherwise spend all month undoing.
Common questions
How much does it cost to run a dehumidifier per month?
Roughly $10–15 for a 20–30 pint unit at eight hours a day and 16 cents per kWh, and $23–35 for a 50-pint unit or longer run times. Multiply watts by hours, divide by 1,000, multiply by your rate.
Is it cheaper to run a dehumidifier all the time or in bursts?
Use the humidistat rather than choosing. Set 50% and let it cycle — continuous operation at a low target is the most expensive way to reach an outcome you did not need.
Does a bigger dehumidifier cost more to run?
Per hour, yes; per month, often less. A larger unit reaches the target and idles, while a smaller one runs continuously without ever getting there.
Sources
- US EPA — Mold and moisture guidance — the 30–50% range and the 10 sq ft remediation threshold
- ASHRAE Standard 55 — Thermal environmental conditions for human occupancy — indoor comfort and humidity limits
- US DOE 10 CFR 430 — Dehumidifier test procedure — the 2019 move to 65 °F rating conditions