How long should you run a dehumidifier for? Experts reveal the sweet spot for reducing damp, mould and condensation

How long should you run a dehumidifier for? If you've recently bought one of these damp-busting machines, you're probably asking yourself this question – particularly if you're worried about them racking up your energy bills or causing a safety hazard.

While the best dehumidifiers can be pretty cheap to run (our favourite below costs just 6p per hour), and they're usually fitted with an auto shut-off feature to prevent any accidents, it's still worth knowing when it's time to turn one off.

Below, our air quality experts reveal the optimum amount of time to run a dehumidifier and answer other commonly asked questions.

How many hours a day should you run a dehumidifier for?

Unfortunately, this isn't a one-size-fits-all answer. According to Chris Michael, founder of Meaco, it all depends on how damp your home is and how much moisture your everyday activities produce.

The good news is lots of dehumidifiers know when it's time to turn off.

"A dehumidifier with a humidistat takes the guesswork out of it," explains Chris. "It stops extracting moisture when the air reaches your chosen humidity and restarts when needed, avoiding unnecessary use."

So, what relative humidity level should your home be? Chris recommends aiming for 55% in UK homes, which will help control condensation and discourage mould.

Can you leave a dehumidifier on all day or overnight?

Potentially, but this will depend on the specific model you have, so you'll need to check your manufacturer's instructions before running it unattended.

While many dehumidifiers will automatically switch off once the room reaches the set humidity level or the water tank is full, Simon Trenerry, Technical Advisor at Safeguard, says to take the following precautions first:

• Position the appliance on a stable, level surface with sufficient space for airflow
• Keep it away from curtains, bedding and other obstructions
• Plug it directly into a wall socket rather than an extension lead
• If using continuous drainage, check that the hose is secure and water can drain safely
• Never use a damaged or malfunctioning appliance

However, there's not much point in running your dehumidifier continuously if your home is already within the recommended humidity range – you'll just be wasting energy unnecessarily.

"Remember, a dehumidifier should be part of a wider approach to moisture management, alongside adequate ventilation, appropriate heating and property maintenance," Simon adds. "If damp or mould keeps returning, identifying and addressing the source of moisture is more effective than continually removing it from the air."

Shop the Homebuilding team's favourite dehumidifiers

How do you know when to turn a dehumidifier off?

While most dehumidifiers come with a built-in humidistat that will automatically turn the device off for you, you can stop using it once the relative humidity reaches between 40% and 60%, explains Simon Trenerry. A digital hygrometer can help you monitor this.

"There are also practical signs that humidity is improving, such as less condensation on windows, fewer musty smells and laundry drying more quickly," he adds. "However, if humidity rises quickly after switching the dehumidifier off, it's important to investigate why. Poor ventilation, everyday activities, leaks or defects in the building could all be contributing factors."

To conclude, there isn't a set number of hours you should run your dehumidifier – you just need to keep an eye on your home's humidity levels.

Found this helpful? You may want to read our guide on how dehumidifiers work. Or, if you're wondering what else they can do, find out whether dehumidifiers can help to reduce dust in your home.