A typical portable dehumidifier draws 300-700 watts depending on its pint rating, and a mid-size 30-50 pint compressor unit running 10 hours a day in a damp basement pulls about 480W – 4.0 amps at 120V – which works out to roughly $26 a month and $315 a year, using about 18 cents per kWh, the U.S. national average residential rate (EIA, 2026). Your own number depends on capacity, runtime, and local electricity price, but the shape of the calculation is the same everywhere, and it is worth doing once with your own numbers.
Dehumidifiers run on a standard 120V outlet, not the 240V circuit that a clothes dryer or electric range needs. That keeps the amperage low even at the top of the wattage range: a 700W unit still draws under 6 amps. The cost comes from runtime, not current.
Watts and amps by pint capacity
Pint capacity is a removal-rate rating, not a power rating, but the two track loosely because bigger compressors need more watts to move more moisture. Use this as a starting point, then check the nameplate on the unit itself – it is more reliable than the box.
| Appliance | Watts | Amps at 120V |
|---|---|---|
| 20-30 pint compressor dehumidifier | 300 W | 2.5 A |
| 30-50 pint compressor dehumidifier | 480 W | 4.0 A |
| 50-70 pint compressor dehumidifier | 700 W | 5.8 A |
| Desiccant dehumidifier (15-20 pints/day) | 300-650 W | 2.5-5.4 A |
For comparison against other appliances that run for hours at a time on the same circuit, see the appliance wattage chart and the refrigerator wattage breakdown – a basement fridge or chest freezer sharing a circuit with a dehumidifier is a common reason a breaker trips that has nothing to do with the dehumidifier itself.
Compressor vs desiccant: different wattage, and temperature decides the cost
Compressor dehumidifiers work like a small refrigerator: a motor compresses refrigerant, cold coils condense moisture out of the air, and the unit is efficient above roughly 65°F. Below that, coils frost over and removal rate drops even as the compressor keeps drawing full current – which is exactly the temperature range of most basements and garages for half the year.
Desiccant dehumidifiers use a rotating wheel coated in a moisture-absorbing material and a heating element to regenerate it. That heating element makes them hungrier: a typical home desiccant unit draws about 300-650W to remove 15-20 pints a day, roughly twice the watts of a compressor unit with similar capacity at room temperature, so in a warm room they cost more per pint removed. In a cold basement the picture flips. Below roughly 50-60°F a desiccant unit usually removes more water per kWh, because its output holds up in the cold, while a compressor unit frosts, stops to defrost and loses capacity.
The humidistat is what actually sets your bill
Nameplate wattage is the draw while the compressor is running, not a continuous figure. Every dehumidifier with a humidistat cycles off once the room reaches the target relative humidity, then restarts when humidity climbs back up. A unit rated at 480W might have an average draw closer to 250-300W over a full day if it is only running half the time, or the full 480W for most of the day if the space is unusually damp or the target humidity is set aggressively low.
This is the single biggest variable in the cost calculation, and it is set by you, not the manufacturer. Setting the humidistat to 50% relative humidity rather than 35% can cut runtime – and cost – substantially, with no real difference in comfort for most basements.
Why an oversized unit can cost less than an undersized one
It seems backwards, but a dehumidifier sized correctly for the room, or slightly larger, often costs less to run over a month than one that is too small. A correctly sized unit pulls the room down to its target humidity quickly, then cycles off for long stretches. An undersized unit never quite catches up – it runs near-continuously trying to close a gap that keeps refilling from a damp slab or poor ventilation, and a unit running at 90% duty cycle at 350W can cost more over a month than a larger unit running at 40% duty cycle at 600W.
As a rule of thumb, size for the square footage and dampness level on the manufacturer’s chart, then round up half a size rather than down if you are between two capacities.
Running amps, startup surge, and the breaker
Compressor dehumidifiers pull a startup surge of 2-3 times their running amps for a fraction of a second when the compressor kicks in – a 480W/4.0A unit can spike toward 10-12A momentarily. That surge is what occasionally trips a shared circuit and what an undersized power strip or extension cord can struggle with; it is rarely a problem for the branch circuit itself.
Under NEC 210.20, a circuit should carry no more than 80% of its rating as a continuous load, so a 15A circuit is good for 12A continuous and a 20A circuit for 16A. A 700W/5.8A dehumidifier leaves comfortable headroom on either size circuit on its own or with a box fan. A sump pump is different: it draws about 4-10A running, with a higher surge each time it starts, so a dehumidifier and a sump pump together can exceed a 15A circuit, and a tripped breaker stops the pump just when the basement needs it. Keep the sump pump on its own circuit; pump makers commonly recommend one and local code requirements vary, so have a licensed electrician add a circuit if there is not one already. The other common conflict is a second heavy 120V load like a space heater or a second dehumidifier on the same run. If you want to work the numbers for your own combination of appliances, the watts-to-amps calculator does the arithmetic directly.
Working out your own monthly and annual cost
The math is: watts x hours run per day ÷ 1,000 = kWh per day, then multiply by your rate per kWh. Using 18 cents per kWh throughout this article, about the U.S. national average (EIA, 2026):
- Small unit, 300W, 6 hours/day: 1.8 kWh/day, about $9.72/month, $118/year.
- Mid unit, 480W, 10 hours/day: 4.8 kWh/day, about $25.92/month, $315/year.
- Large unit, 700W, 12 hours/day: 8.4 kWh/day, about $45.36/month, $552/year.
Check your own utility bill for your actual per-kWh rate – it varies by region and season, sometimes by a factor of two. For a broader look at what a kWh is actually worth to you when comparing running costs against buying equipment outright, the power station price index lays out the cost-per-kWh comparison in more depth.
Running a dehumidifier on battery backup
Because a compressor dehumidifier’s startup surge is well within what a mid-size power station can handle, it is a reasonable load to put on home battery backup during a short outage, provided the unit’s continuous wattage and the surge headroom both fit the station’s rated output – not just its capacity in Wh. If you are pricing out a system that needs to carry a dehumidifier alongside other basement loads like a sump pump, sizing a solar system walks through matching daily kWh use, not just peak watts, to battery capacity.
None of these figures come from bench testing – they are drawn from typical manufacturer nameplate ratings and the arithmetic above, and your own unit’s label is the most accurate number you will find for it.