Why a damp home can cost more to heat
A damp home often feels colder than the thermostat says. Most of that comes from what the damp does to surfaces and fabrics, rather than from the moisture in the air itself.
- Wet walls lose more heat. Laboratory tests for the government's research into internal wall insulation found that wet bricks had higher heat loss than dry bricks. A wall kept damp by condensation lets more of your heating escape.
- Damp fabrics feel cold. Bedding, sofas and clothes that pick up moisture feel chilly and clammy against your skin, and it's tempting to turn the heating up to make up for it.
- Moist air takes slightly more energy to warm. Water vapour holds more heat than dry air does, but the amount is small next to the heat lost through walls, windows and draughts.
Only the first of these is likely to make a difference you would notice on a bill, and only if your walls are wet from condensation. If they are wet from rain getting in or from rising damp, a dehumidifier won't dry them for long. That needs a repair. See the types of damp.
What the dehumidifier costs to run
Here is a worked example using a 12 litre compressor model (Pro Breeze OmniDry 12L), rated at 200W, running 6 hours a day:
| Period | Cost |
|---|---|
| Per hour | 5.3p |
| Per day (6 hours) | 32p |
| Per month | £9.60 |
| Over a 26-week winter | £57.48 |
A desiccant model costs more. The Meaco DD8L, at 650W, would cost £186.82 over the same winter. Both figures assume the machine works flat out for every one of those hours. With the humidistat set to 50 to 60%, it cuts back once the room is dry, so the real cost is often lower.
Costs use 26.32p per kWh, the Ofgem price cap, Direct Debit average for England, Scotland and Wales for 1 October to 31 December 2026. Your own tariff may differ. How we calculate.
Running cost calculator Put in your own dehumidifier's wattage and hours to see what it costs you.Where the electricity goes
Almost all the electricity a dehumidifier uses ends up as heat in the room. It also releases the heat that went into turning the water into vapour, as the water turns back into liquid. That heat came out of your room when the water evaporated, so it is a refund rather than a gift, but it does mean a dehumidifier gives off a little more heat than the electricity it uses. In winter, that warmth isn't wasted.
The catch is the price. At the current cap, a kWh of electricity costs about 3.3 times as much as a kWh of gas. A boiler loses some heat up the flue, so the real gap is a little smaller, but heat from a dehumidifier still costs more than heat from gas central heating. If you heat with plain electric heaters, it is a different story: the dehumidifier's warmth costs no more than theirs, and you get the drying as well.
When it's worth running one
- You have condensation, a musty smell or mould. Fixing that is the main reason to own one.
- You dry washing indoors. A dehumidifier stops that water ending up on your walls, and usually costs less than a tumble dryer. See drying clothes indoors without damp.
- You heat with electric heaters, so the dehumidifier's warmth costs about the same as theirs.
- A cold room needs drying. A desiccant model's heat is useful there.
When it isn't
- Your home already sits between 40 and 60% humidity with no condensation. Running one then mostly costs money. A cheap hygrometer will tell you; see ideal indoor humidity.
- You're running it only in the hope of a lower gas bill.
- The damp is from a leak, rain getting in or rising damp. That needs fixing at the source.
Cheaper ways to cut damp and heating costs together
- Open trickle vents and use extractor fans when cooking and showering, so moisture leaves before it settles.
- Keep a low, steady background heat in cold rooms rather than heating them hard now and then. Warmer walls collect less condensation.
- Draught-proof doors and letterboxes, and use film on single glazing. See draught excluders and window film.
- Dry washing in one closed room, not across the house.
Sources
Checked 14 October 2026.