Basement Dehumidifier Running Cost Calculator

Getting a running cost takes four quick entries. The tool turns watts into kilowatt hours, then into dollars.

1. Enter the power draw in watts from the rating label on the back or bottom of your unit. A 50 pint basement unit usually draws about 500 watts.
2. Enter the hours the compressor actually runs each day, not the hours the unit is switched on. A unit with a humidistat cycles off when the room reaches its target.
3. Enter your electricity rate in dollars per kWh from your bill, and the days you run it in a month.
4. Press Calculate, or press Enter. The monthly cost appears first and large, with the daily cost, the daily kilowatt hours and the yearly cost below. Press Reset to clear the form and start over.

The formula has three short steps. First, turn watts into kilowatts. Kilowatts = watts / 1,000. A 500 watt unit draws 0.5 kilowatts. Second, work out the energy used in a day. Daily kWh = kilowatts x hours running per day. At 12 hours a day, that is 0.5 x 12 = 6 kWh. Third, turn energy into money. Daily cost = daily kWh x electricity rate. At $0.17 per kWh, that is 6 x $0.17 = $1.02 a day. Monthly cost is the daily cost times the days you run it, and yearly cost is the daily cost times 365.

The same three steps work for any appliance that runs on a steady power draw. If you heat a damp space as well, our greenhouse heating cost calculator uses the same watts to dollars math for a heater.

A 50 pint basement dehumidifier draws 500 watts, runs 12 hours a day, and the electricity rate is $0.17 per kWh. It runs 30 days a month. Here is exactly what the calculator does.

1. Kilowatts: 500 / 1,000 = 0.5 kW.
2. Daily energy: 0.5 x 12 = 6 kWh per day.
3. Daily cost: 6 x $0.17 = $1.02 per day.
4. Monthly cost: $1.02 x 30 = $30.60 per month. Yearly cost: $1.02 x 365 = $372.30 per year.

As a second check, the same unit running 24 hours a day uses 12 kWh a day, which costs $2.04 a day and $61.20 a month at the same rate. That matches the published example for a 500 watt unit at $0.17 per kWh, so the steps are right.

The most common mistake is to multiply the wattage by 24 hours when the unit does not run at full power all day. A dehumidifier works in cycles. It pulls moisture until the air reaches the humidity you set, then it idles or switches off. A unit that is switched on 24 hours a day but only runs half the time costs half the 24 hour figure.

That is why the calculator asks for the hours the compressor actually runs. In a moderately damp basement, 8 to 12 hours a day is typical. In a very wet basement after rain, or in a basement with no vapor barrier, the unit may run close to 24 hours a day until the space dries out. Start with your best guess, then check the real run time over a week and enter that number instead.

Set the target humidity between 30 and 50 percent. Below 30 percent the air feels dry and the unit works harder than it needs to. Above 50 percent, mold and musty smells come back. A $15 hygrometer on the basement wall tells you where you stand.

Bigger units draw more power, but they also finish the job faster, so size alone does not decide the bill. The table below uses 12 hours a day at $0.17 per kWh.

Your electricity rate moves the result just as much as the wattage. The same 500 watt unit at 12 hours a day costs about $21.60 a month at $0.12 per kWh and about $55.80 a month at $0.31 per kWh. Always use the rate on your own bill, because rates vary a lot by state.

Buy the right size for the space. A unit that is too small runs all day and never reaches the target humidity, while a unit that is too large cycles on and off and wastes power on starts. For a moderately damp space up to 1,500 sq ft, a 30 pint unit is usually enough. For a wet basement up to 2,500 sq ft, a 50 pint unit fits better.

Fix the moisture before you fight it with power. Seal cracks, grade the soil away from the foundation, and keep gutters clear, because every gallon that leaks in is a gallon the dehumidifier must pull out of the air. Clean the filter every few weeks, and use a drain hose instead of a bucket so the unit never stops on a full bucket. If you are finishing the basement around the unit, our concrete calculator and brick calculator cover the materials for the floor and walls that often go with the job.