Calculate the running cost of any dehumidifier and compare models without relying on an outdated energy-price assumption.
The running-cost formula
Find the appliance's power in watts and your electricity price in pence per kilowatt-hour. Multiply watts by hours used, divide by 1,000, then multiply by your tariff.
For example, a 200-watt appliance running for five hours uses 1 kilowatt-hour. Multiply that 1 kWh by the current unit price shown on your bill. This example explains the calculation; it is not a prediction of what every machine will consume.
Rated power is not always constant use
A humidistat-controlled compressor may cycle once the target humidity is reached, so its average use over a day can be below the simple maximum calculation. Laundry or continuous modes may run harder for longer.
Use a plug-in energy monitor if you want a household-specific figure, provided it is correctly rated and used according to its instructions.
Compare a completed job, not one hour
A machine drawing fewer watts may take longer to remove the same moisture. Record the energy used for one representative laundry load or one day of humidity control, then compare that completed task across settings.
Reduce waste before replacing the machine
Clean the filter, avoid blocking airflow, close the laundry room during an intensive cycle and use a higher washing-machine spin where fabric care allows. Set a sensible humidity target instead of running continuously without a reason.
What to check before buying
Look for published power consumption at realistic conditions, an effective humidistat, timer or laundry programme, and a clear low-temperature performance table. A cost claim without its tariff and test setup is difficult to compare.
Common questions
Is it cheaper to run a dehumidifier overnight?
Only if your tariff has cheaper off-peak electricity. Check your own tariff and never compromise safe placement or supervision instructions.
Does a dehumidifier use less electricity when the tank is nearly full?
The tank level is not a useful efficiency control. Most machines stop when full; empty it safely so the planned cycle can finish.
Sources and notes
Our editors reviewed the following material when preparing this guide. Manufacturer sources are used for operating details and are checked against independent public guidance where available.
Last meaningfully updated 14 August 2026.