Heating and damp, cost per hour
Dehumidifier running cost, per hour and per winter
A dehumidifier is one of the few appliances people buy specifically because they have been told it is cheap to run. It is, per hour. It is also on for hundreds of hours, which is the part that decides what it costs.
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Per hour, it really is cheap
A compressor unit costs about 5.22p an hour to run and a desiccant one about 13.1p. Nobody would object to either figure. The number that matters is what happens when you multiply it by a season.
| Option | Running | Cost per hour | Relative |
|---|---|---|---|
| Bathroom extractor fan20W, run properly | 0.52p | 1.36p | |
| Compressor dehumidifier300W, cycling | 5.22p | 8.21p | |
| Desiccant dehumidifier600W, mostly on | 13.1p | 16.2p |
At six hours a day across a five month damp season, a compressor dehumidifier costs about £47 in electricity and a desiccant one about £117. Those are the numbers to weigh against whatever the damp is costing you, and against the alternatives further down this page.
Compressor or desiccant
A compressor unit pulls warm moist air over a cold coil and collects what condenses. That works well in a heated room and progressively worse as the room gets colder, because there is less moisture in cold air to condense and the coil ices up. A desiccant unit passes air over a moisture absorbing wheel and then heats the wheel to drive the water off, which works at any temperature and costs more than twice as much per hour.
If the room is heated, buy a compressor unit and pay 5.22p an hour. If it is a garage, a caravan, a conservatory or an unheated back bedroom, buy a desiccant one, because a compressor unit in a cold room is a machine that runs constantly and removes very little. The waste heat from a desiccant unit is also not entirely wasted in winter.
Drying laundry indoors is the usual reason
A heated airer costs about 31p a load to run and puts roughly two litres of water into the room. Running a compressor dehumidifier alongside it for four hours adds about 21p, so the honest cost of drying that load indoors is closer to 52p than 31p. That still beats a vented tumble dryer at £1.17 and it is a good deal worse than the airer looks on its own.
The cheapest fix is usually not a dehumidifier
A 20W extractor fan run for twenty minutes after every shower costs a fraction of a penny and removes the moisture at source, before it has condensed on a cold wall in another room. Most household damp is produced in two rooms and shows up in a third. Dealing with it where it is made is cheaper than dealing with it where it lands, and no appliance on this page will out-perform opening a window for ten minutes on a dry day.
The verdict
Ventilate first, because it is free. Extract at source second, because it is nearly free. Buy a compressor dehumidifier if the problem is in a heated room and a desiccant one if it is not. And if you are buying one only to dry washing, add its running cost to the airer's before deciding the airer was the cheap option.
Put your own numbers in
Prefilled with a compressor dehumidifier. Change the hours a year to match how you would actually run it.
Cost per meal
Set the purchase price to zero for the running cost alone.
Questions
How much does a dehumidifier cost to run per hour in the UK?
About 5.22p an hour for a 300W compressor unit cycling under humidistat control, and around 13.1p for a 600W desiccant one, at the current capped rate.
How much does a dehumidifier cost to run all winter?
At six hours a day for five months, roughly £47 of electricity for a compressor unit and about £117 for a desiccant one.
Compressor or desiccant dehumidifier, which is cheaper?
A compressor unit costs less than half as much per hour, but it loses effectiveness in a cold room. In an unheated garage or conservatory a desiccant unit is the one that actually works.
Is a dehumidifier cheaper than a tumble dryer?
An airer plus a dehumidifier comes to roughly 52p a load against £1.17 for a vented tumble dryer and 42p for a heat pump one, so it sits between the two.
Will a dehumidifier stop condensation and mould?
It helps, but ventilation and extracting moisture where it is produced deal with the cause rather than the symptom, and both cost close to nothing.
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More heating and damp costs, or read how we work these out.
Prices used on this page
- Electricity, 26.11p per kWh. Ofgem price cap, direct debit, average of England, Scotland and Wales, including 5% VAT.. Ofgem energy price cap unit rates and standing charges. Checked 22 August 2026.