Where to put a dehumidifier (and how long to run it)

Updated 26 October 2026 · Prices worked out at UK electricity rates

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A dehumidifier in the wrong spot can run for hours and barely change anything. These simple rules get the most water out of the air for the least electricity.

Short answer: put it in the dampest room, in the middle of the room or at least 20 to 30 cm from walls and furniture, with doors and windows closed. Set the humidistat to around 50 to 55% and let it switch itself on and off.

Which room

Where the problem is: the room with condensation, mould or a musty smell.
Where you dry washing: the dehumidifier and airer together in a small, closed room is one of the cheapest ways to dry clothes.
A central landing or hallway if you want to treat a whole small house or flat with one unit, leaving internal doors open.

Where in the room

Away from walls and curtains so air can flow in and out freely. Check which side the air intake is on.
Not right next to a radiator or heater, which can confuse the humidity sensor.
On a hard, level surface so the tank sensor works and it doesn't vibrate.
In a bedroom, as far from the bed as practical, and use night mode.

Doors and windows

Keep the doors and windows of that room closed while it runs. Otherwise it is trying to dry the air coming in from outside, which in a British winter is often at 80 to 90% humidity.

How long to run it

For a damp room, run it continuously for the first few days, then let the humidistat take over. Once the room sits at 50 to 55% it will usually only run a few hours a day. For washing, run it on laundry mode until the clothes are dry, usually 4 to 8 hours.

Running costs depend on the type: see the sums in our desiccant vs compressor guide.

Looking after it

Empty the tank daily, or fit a drain hose to a sink.
Vacuum or rinse the air filter every couple of weeks.
Don't use the collected water for drinking; it is fine for watering plants that aren't edible.