Dehumidifier Running Cost Calculator UK 2026

A dehumidifier is one of the cheapest appliances in the house to run and one of the most misunderstood. People assume it is on a par with a tumble dryer or a fan heater, when a typical 300W desiccant unit costs pennies an hour. The maths is unusually simple: wattage times hours gives you watt-hours, divide by a thousand for kilowatt-hours, multiply by your unit rate.

The important detail is that the nameplate wattage is a maximum, not a constant. Compressor dehumidifiers cycle — the compressor stops once the target humidity is reached and only the fan runs, so real-world consumption is often 50-70% of the rated figure. Desiccant models draw closer to their rating continuously but work better in cold rooms, which is why they suit unheated garages and conservatories.

Running a dehumidifier can actually cut your total bill. Dry air heats faster and holds warmth better than damp air, and drying laundry indoors with a dehumidifier costs substantially less than a vented tumble dryer cycle. Where it stops being economical is leaving a large unit running 24/7 in a house with an unresolved damp source — fix the cause, then dehumidify the consequence.

Set the humidistat to 50-55% rather than the lowest setting, run it in a closed room, and empty or plumb the tank so it does not shut off early. Those three habits usually halve the number this calculator gives you.