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Stop streaming windows, black mould and washing that never dries.
If you’re wiping windows every morning, or waiting three days for washing to dry, the problem isn’t your heating. It’s the amount of water sitting in your air.
A family of four puts around 10 litres of moisture into the air every day just by cooking, showering and drying clothes indoors. In winter that lands on the coldest surfaces in the house – window frames, external walls, behind wardrobes – and that’s where black mould starts.
A dehumidifier takes that water back out before it can settle. This guide helps you work out which problem you’ve got, what should fix it, and what it costs to run.
Find the problem you actually have, and we’ll tell you what fixes it.
The cause: warm, moist air hitting cold glass overnight. No amount of wiping fixes it, because the water’s in the air, not on the window. Pull the humidity down to 40–60% and the glass should stay dry on its own.
Stop feeding it: mould needs sustained damp to grow. Cleaning it off treats the symptom; holding humidity below 60% takes away what it needs to come back.
Laundry Mode: runs the fan hard to lift moisture straight off the fabric. Clothes dry in hours rather than days, usually for less electricity than a tumble dryer – and the water ends up in the tank instead of your walls. Shop laundry mode.
Trapped moisture: that smell is damp in soft furnishings and plaster in a room with no air movement. Closed doors and no heating make it worse. A few hours a day of drying clears it and keeps it clear.
Desiccant technology: a standard compressor model struggles below 15°C. A desiccant uses a moisture-absorbing wheel instead, so it works just as hard in the cold – and returns around 10°C of warmth while it runs. The right answer for garages, conservatories, caravans and boats. Shop desiccant.
It doesn’t run all day: set a target humidity and the humidistat switches the unit off once the room reaches it, so it only works when it needs to. Most domestic models draw 180–320W – less than a games console. Shop low energy.
HEPA air purifying: dust mites and mould spores both need humid air to thrive. Drying the room makes it hostile to them, and a HEPA filter captures what’s already airborne while it works. Shop air purifying.
Continuous drainage: most models take a drain hose, so you can run it to a sink or drain and never touch the tank. Useful in a utility room, garage or anywhere the unit runs unattended.
Night mode: look for a quiet or sleep setting. It drops the fan speed and dims the display so the unit keeps working through the night without the noise or the glow.
Speed limits the damage: water left in plaster, screed and joists is what turns a leak into a repair bill. A high-capacity unit run hard for a few days pulls it back out. Shop commercial.
This is the question that decides the size. One bedroom with streaming windows is a very different job from a house where every external wall feels cold and damp.
Rough guide: up to 10L clears one or two rooms in a flat. 12–20L handles a typical 2–3 bedroom house. 20L+ suits larger or badly affected homes, and 40L+ is trade territory.
Undersize it and it runs constantly without ever winning. Open doorways, open-plan layouts and unheated hallways all enlarge the job, so if you’re between two sizes, take the bigger one.
Get this wrong and the machine can underperform whatever size you bought. A compressor model condenses moisture on a cold coil, so it needs the room warmer than that coil – roughly 15°C and above.
A desiccant model uses a moisture-absorbing wheel instead, so its performance barely drops in the cold, and it returns around 10°C of gentle warmth to the room as a side effect.
Compare our range side by side.
Reliable and effective moisture extraction for everyday home use.
Upgraded efficiency featuring Laundry Mode, Quiet operation, and Low Energy design.
Premium features including Smart Wi-Fi, Laundry Mode, Quiet operation, and extreme efficiency.
Rugged, high-capacity machines for trade, restoration and demanding drying jobs.
Description
Three technologies, three very different jobs. Match it to where the unit will actually live.
The right buy for living rooms, bedrooms and anywhere you keep above 15°C. Lowest running cost of the three, and the most extraction per pound spent.
Shop Compressor
Keeps working when a compressor gives up. Buy this for a garage, conservatory, caravan or boat – and it warms the space by around 10°C while it dries it.
Shop Desiccant
When the job is a building site, a gym, or getting a flooded floor dry before it has to come up. Built to run hard, day after day.
Shop CommercialFour worth paying for, and what each one changes day to day.
Laundry mode runs the fan flat out to lift moisture straight off the fabric – usually costs less to run than a tumble dryer, and the water ends up in the tank rather than your walls.
Shop Laundry Mode
Smart Wi-Fi control from your phone or a voice assistant, plus schedules so it runs on off-peak hours instead of whenever you remember.
Shop Smart
HEPA air purifying captures the dust, pollen and mould spores already in the air, while the drying removes the damp those allergens need to thrive.
Shop Air Purifying
A humidistat switches the unit off the moment the room hits your target, so you’re not paying to dry air that’s already dry. The single biggest lever on running cost.
Shop Low EnergyCondensation is the visible part. The expensive part happens behind it.
Moisture migrates into plaster, timber and insulation. Replastering one wall can cost more than any dehumidifier on this page.
Damp air takes more energy to warm than dry air, and it robs heat back off your skin. Dry the room and the same thermostat setting feels warmer.
Damp homes carry more mould spores and dust mites, both common triggers for asthma and allergies. Winter is when it peaks.
Clothes in wardrobes on external walls, books, tools in the garage, anything in storage. Mould finds them long before you notice the smell.
As a rough guide, a 10L model suits a one or two bedroom flat, 12–20L covers most 2–3 bedroom houses, and 20L+ suits larger homes or serious damp. Use the calculator above for a recommendation based on your actual room size, damp severity and temperature.
A compressor model condenses moisture on a cold coil and is the most efficient choice in heated rooms above roughly 15°C. A desiccant model uses a moisture-absorbing wheel, so it keeps working in cold spaces and gently warms the room as it runs.
A desiccant dehumidifier. It works just as well in the cold as in the warm, is lighter than a compressor model, and is happy running unattended for long periods while the vehicle is laid up.
It can. Dust mites and mould both thrive in humid air, so bringing humidity down to 40–60% makes your home far less hospitable to them. Many of our dehumidifiers also carry HEPA filters that capture mould spores, dust and bacteria from the air.
Most domestic compressor models draw between 180W and 320W, which is around 40p to 75p for eight hours at 29p per kWh. Desiccant models draw more power but return heat to the room. The calculator above gives an estimate for your chosen size.
In most cases yes. A dehumidifier on laundry mode typically uses a fraction of the power of a vented or condenser tumble dryer, and it protects the room from the moisture the clothes give off while they dry.
Between 40% and 60% relative humidity. That’s low enough to stop condensation, mould and dust mites, without drying the air so far that it becomes uncomfortable.
