Quick answer: A compact compressor dehumidifier (10 to 12 litres a day) draws about 180 W, roughly 4.7p an hour under the Ofgem price cap of 26.32p per kWh, or about £11.37 a month at 8 hours a day. Desiccant models use more power but work better in cold rooms.
Dehumidifier running costs by type
| Dehumidifier | Power | Hours a day | UK per hour | UK per day | UK per month |
|---|---|---|---|---|---|
| Compressor, 10 to 12 litres a day | 180 W | 8 | 4.7p | 38p | £11.37 |
| Compressor, 20 litres a day | 350 W | 8 | 9.2p | 74p | £22.11 |
| Desiccant, 7 to 10 litres a day | 600 W | 8 | 16p | £1.26 | £37.90 |
Compressor or desiccant?
- Compressor models are cheaper to run in a normal living space, but lose effectiveness in cold rooms (below about 15°C).
- Desiccant models draw more power but keep working in cold garages, conservatories and unheated bedrooms, and give off a little warmth.
Drying washing: dehumidifier vs tumble dryer
Drying a load on an airer in a closed room with a 180 W dehumidifier for 6 hours uses about 1.1 kWh, around 28p. A condenser tumble dryer uses about 4.5 kWh, around £1.18. See tumble dryer costs.
How to run it for less
- Set the humidistat to about 50 to 60% instead of running it continuously.
- Close doors and windows in the room you are drying.
- Deal with the source: extractor fans, ventilation, leaks.
- Use laundry mode only when you dry washing.
Dehumidifier cost calculator
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Frequently asked questions
Should I leave a dehumidifier on all day?
Leave it on with the humidistat set and it will cycle on only when needed. Running it flat out all day rarely helps.
Does a dehumidifier help with condensation and mould?
Yes, it reduces condensation, but fixing ventilation and leaks deals with the cause. For persistent mould in a rented home, report it to your landlord.
A real example: drying a flat in winter
A compact 180 W compressor dehumidifier running 8 hours a day uses 43 kWh a month, about £11.37. A 650 W desiccant model running the same hours uses 156 kWh, about £41.06, but it works better in an unheated room below about 15°C.
If you dry washing indoors, running the dehumidifier in the same small room for a few hours is usually much cheaper than a tumble dryer load, which costs around £1.18.
Damp, condensation and when to call a professional
Condensation on windows in the morning is common in winter and a dehumidifier helps a lot. Damp patches that stay wet, a musty smell that does not go away, or tide marks low on walls can mean rising damp, a leak or a ventilation problem. If you rent, report damp and mould to your landlord in writing; landlords must deal with serious hazards.
More questions readers ask
What humidity should my home be?
Aim for roughly 40 to 60% relative humidity. Below about 40% the air can feel dry, above 60% mould becomes more likely.
Do I need a dehumidifier if I have extractor fans?
Use the fans first when cooking and showering. A dehumidifier helps where fans are missing, when drying washing indoors, or in rooms with persistent condensation.
Sources
- Ofgem, Energy price cap.
- Our methodology.