Running costs updated 1 October 2026. Every electricity figure on this page is costed at the Ofgem price cap average electricity unit rate of 26.32p per kWh, which applies from 1 October to 31 December 2026. Your own tariff may be higher or lower, so check your latest bill before relying on these numbers.
Quick answer: yes. Modern dehumidifiers are designed to run unattended, and they switch off automatically when the tank is full. Set the humidistat to 50–55% so it is not running flat out, give it clear space and plug it straight into a wall socket. Running a 151W compressor model for 8 hours costs about 32p at 26.32p per kWh.
Overnight is when condensation forms. The heating goes off, the windows get cold and everyone in the house is breathing out moisture for eight hours. So it makes sense to want the dehumidifier on while you sleep. The questions people actually ask are whether it is safe, whether it is a waste of money, and whether it will keep them awake. Here are straight answers to all three.
Is it safe to leave a dehumidifier on overnight?
Dehumidifiers sold in the UK are built to run for long periods unattended, much like a fridge. The safety features that matter for overnight use are:
- Automatic shut-off when the tank is full. It is standard on mainstream dehumidifiers: the machine stops rather than overflowing. Check the spec sheet if you are buying an unbranded one.
- A humidistat that cycles the machine off once the room reaches the level you set.
- Auto-defrost on most compressor models, which stops ice building up on the coil in cooler rooms.
Good sense still applies, as with any electrical appliance left on:
- Plug it directly into a wall socket, not a coiled extension reel or a multi-way adaptor shared with heaters.
- Keep 20–30cm clear around it and never cover the air inlet or outlet. Keep it away from curtains, bedding and clothes.
- Stand it on a hard, level floor so it cannot tip and the water sits properly in the tank.
- Clean the filter regularly. A clogged filter makes the machine work harder.
- Check the cable and plug for damage, and register the product so you hear about any recalls.
Desiccant models blow out air a few degrees warmer than the room. That is normal, but it is another reason to keep the outlet clear of fabrics.
How much does it cost to run overnight?
At the Ofgem price cap rate of 26.32p per kWh, assuming full power for the whole night:
| Dehumidifier | Power | 8 hours | Every night for a month |
|---|---|---|---|
| MeacoDry Arete One 12L | 151W | 31.8p | £9.67 |
| Devola 12L | 185W | 39.0p | £11.84 |
| MeacoDry Arete One 20L | 216W | 45.5p | £13.83 |
| Meaco DD8L Zambezi (desiccant) | 600W | £1.26 | £38.41 |
A month here is 30.4 nights. Real costs are usually lower: with the humidistat at 50–55%, a compressor cycles off for long stretches once the room is dry. A desiccant left on all night is where costs add up, which is why I suggest running desiccants for a few hours in the evening instead. Work out your own figures with the dehumidifier running cost calculator.
Do you actually need it on all night?
Often not. For most bedrooms, two or three hours in the evening with the door shut removes most of the moisture, and the room stays below the condensation point until morning. Leaving it on overnight makes sense when:
- You are drying washing in the room. See how long a dehumidifier takes to dry clothes.
- You are tackling existing mould and want humidity held low for a couple of weeks. My guide to the best dehumidifier for mould and condensation covers the method.
- The room is a cold bedroom that runs with water by morning even after an evening run.
Otherwise, a timer is the better tool: most models have one, and some, like the Meaco DD8L, have a Daily Run function that repeats every day.
Will it keep me awake?
That depends on the model. The quietest compressor dehumidifiers are rated around 35–38 dB, which most people can sleep through, especially with a night mode that dims the display. Machines rated 42 dB and up are better suited to a hallway. My guide to the best quiet dehumidifier for bedrooms ranks them by stated noise.
Will the tank overflow overnight?
No. It will switch off when full, which is the real problem: it stops working at 3am and the humidity climbs back. Empty the tank before bed, or set up continuous drainage with a hose to a sink, shower tray or floor drain. In a very damp room, a model with a bigger tank, such as the Arete One 20L (4.8L), lasts longer.
Best settings for overnight use
| Setting | What I would use |
|---|---|
| Humidity target | 50–55% |
| Mode | Night or sleep mode if available; laundry mode only if drying washing |
| Fan | Low |
| Position | Hard floor, 1–2m from the bed, outlet facing away from you |
| Door | Shut, with a trickle vent cracked open |
Dehumidifier and drying guides
By room and problem
- Best dehumidifier for a cold bedroom
- Best quiet dehumidifier for bedrooms
- Best dehumidifier for a conservatory
- Best dehumidifier for a 2-bed house
- Best dehumidifier for mould and condensation
Choosing one
Drying clothes for less
- How long a dehumidifier takes to dry clothes
- Dehumidifier vs tumble dryer cost
- Heated airer vs tumble dryer cost
- Do heated airers actually save money?
Not sure what size you need? Try the dehumidifier size calculator.
Frequently Asked Questions
Is it safe to leave a dehumidifier on all night?
Yes, provided it is in good condition, plugged directly into a wall socket, has clear space around it and is on a level floor. Dehumidifiers are designed to run unattended and switch off automatically when the tank is full.
How much does it cost to leave a dehumidifier on overnight?
At 26.32p per kWh, about 32p to 46p for eight hours on a 151–216W compressor model at full power, and around £1.26 for a 600W desiccant. The humidistat usually brings the real figure down.
Should I run a dehumidifier at night or during the day?
Evenings and nights are usually best, because that is when moisture from cooking, showers and breathing peaks and condensation forms. A few hours before bed is often enough.
Can I leave a dehumidifier on when I go out?
Yes, the same safety points apply. Set the humidistat so it cycles off, empty the tank or use continuous drainage, and keep the area around it clear.
Does a dehumidifier make a bedroom cold at night?
No. Compressor models return air at about room temperature, and desiccant models make it slightly warmer. Drier air often feels more comfortable at the same temperature.
