Dehumidifier Running Cost Calculator: Watts, Pint Size and Monthly Bill

The formula

A compressor dehumidifier is a small air conditioner that puts its own heat back into the room. Its electricity use follows the same rule as any appliance:

kWh per day = Watts × Compressor hours per day ÷ 1,000
Cost per month = kWh per day × Days × Rate ($/kWh)
Annual cost = Cost per month × Months of use per year

The hours that matter are the hours the compressor actually runs. Most units have a built-in humidistat that shuts the compressor off once the room reaches the setpoint, though the fan may keep running at a much lower draw (often 30–80 W). Use the wattage from the label or a plug-in watt meter if you have it; the size options in the calculator are typical values.

Worked example

With the calculator defaults, a medium 35-pint unit drawing about 450 W, running 12 hours a day at $0.17/kWh:

1. Energy per day: 450 × 12 ÷ 1,000 = 5.4 kWh
2. Cost per day: 5.4 × $0.17 ≈ $0.92
3. Per 30-day month: 162 kWh, about $27.54
4. Over 6 months of use a year (the default): 972 kWh, about $165 a year

A large 50-pint unit at 650 W on the same schedule uses 234 kWh a month, about $40. Whole-house units cost more per hour but often remove more water per kWh and serve several rooms.

Typical wattage by size

In 2019, DOE moved the pint-rating test from 80 °F to 65 °F at 60% relative humidity, closer to a real basement. Cooler air holds less water, so the same machine earned a lower number: what used to be sold as a 70-pint unit is now roughly a 50-pint unit. When comparing a new model with an old one, check which rating it uses.

To compare efficiency rather than size, look at the integrated energy factor (IEF) in liters per kWh. Higher means more water removed per unit of electricity. ENERGY STAR models must beat the federal minimum IEF for their class.

What drives run time

• Humidity setpoint: each step lower makes the unit run disproportionately longer. 45–50% relative humidity is enough to control mold and dust mites in most basements; see basement dehumidifier settings and the indoor humidity guide.
• Moisture coming in: open windows, a vented dryer leaking into the space, an unsealed sump pit, wet foundation walls and outside air infiltration all keep it running. Fix the source first.
• Temperature: below about 65 °F, output falls and the coil can ice up, so the unit runs longer while removing less. If yours frosts, see dehumidifier freezing up.
• Drainage: a full bucket stops the unit. A gravity hose to a floor drain or a condensate pump lets it run as needed without you emptying it.

Cost per pint removed

A rough way to compare options is energy per pint. At its rating condition, a 35-pint unit drawing 450 W around the clock uses about 10.8 kWh to remove 35 pints, roughly 0.31 kWh per pint, or about $0.05 per pint at $0.17/kWh. In a cool basement it will remove less water per hour, so the real figure is often higher. Whole-house units and ENERGY STAR models usually do better per pint.

In summer, a central air conditioner also removes moisture. If your AC already keeps the main floors at 50% or below, the dehumidifier may only be needed in the basement. If it doesn't, the problem may be the AC itself; see does AC remove humidity.

Does a dehumidifier make the room warmer?

Yes. All the electricity it uses ends up as heat in the room, and so does the latent heat released when water vapor condenses on its coil. A 450 W unit removing a pint or two an hour can add roughly 2,500–3,500 BTU/h of heat in total. In a cool basement that is harmless or even welcome. On main floors in summer, the air conditioner has to remove that heat again, adding to its running cost, so it is usually better to control humidity through the AC or a ducted whole-house unit than to run portable dehumidifiers in cooled rooms.

Ways to lower the bill

• Set the humidistat to 50% and check it with a separate hygrometer; built-in sensors can be off by several points.
• Close basement windows in humid weather and seal rim joists and gaps around pipes.
• Clean the filter every few weeks so airflow and coil temperature stay right.
• Place the unit away from walls with open space around it, and keep doors to the area closed.
• Replace a very old unit; newer models often remove noticeably more water per kWh.

For other appliance loads, use the appliance electricity estimator.

Frequently asked questions