Best dehumidifiers 2026 UK: whether you need 12L or 20L, what each one costs to run, and the tank test that settles it

Almost every listing in this category is sorted by one number. Ten litres, twelve, twenty, twenty-five. The assumption is that the twenty dries more than the ten, so you buy the biggest one the budget allows. That number does not mean what it looks like it means.

Litres per day is a laboratory figure taken in fixed conditions, and in this category those conditions are usually 30C and 80% relative humidity. That is greenhouse air in August. It is not a hallway in November at 19 or 20C. A compressor machine extracts considerably less as the air gets colder, which is why the retailers themselves warn that refrigerant models struggle in cold spaces.

The interesting part is not that the figure is optimistic. It is that some makers write the conditions down and some do not, so comparing one brand's number with another's is comparing two different things. And there is a way to prove it without taking anyone's word for it, using a second number printed on the same spec sheet.

Now the check that needs nothing but the listing you are already looking at. Every maker publishes two figures side by side: the litres it extracts in a day, and the capacity of the tank that water falls into. Divide one by the other and you get how many times a day you would be emptying it if the big number were true.

Across the whole category the answer is between three and six times a day. Once every four or five hours, through the night included. Nobody designs a household appliance to be used like that, and no maker sells one saying so. The conclusion is not that they are lying: it is that they already know that number is not reached in a house, which is why they fit a tank that would be absurd if it were.

So the practical answer to 12L or 20L is not about the litres at all. A 12 litre machine with a 2 litre tank is designed to be plumbed in; a 20 litre machine with a 5.4 litre tank is designed to be carried to the sink once or twice a day. Pick the one whose tank matches how you are going to live with it, then check the watts.

This is the decision that actually changes what you get, and it is the one where a British buyer is told opposite things by the first results on the page. Two machines with the same name inside a shop do completely different things, and they are separated by two figures that are always on the listing: the unit the extraction is quoted in, and the watts.

One brand's own catalogue lays it out. Cecotec sells a machine of 23 watts rated at 300 millilitres a day and another of 205 watts rated at 10 litres. Thirty-three times the water for nine times the power. In between there is a 45 watt unit at 750 millilitres. The jump is not gradual: it is the moment a compressor appears inside.

This is where the category is either cheap or expensive, and where the published advice gets vague. A consumer testing body puts the average running cost of its recommended machines at around 7p an hour, working from the 26.32p per kWh October 2026 price cap. That average is doing a lot of work: 7p an hour is a 266 watt machine, and the ten machines on this page range from 23 watts to 650.

Run through the cap, the same sum gives 0.6p an hour for the Peltier unit, 5.4p for the 205 watt compressor, 10p for the 380 watt one and 17.1p for the desiccant on boost. That is a spread of twenty-eight times between the cheapest and the dearest machine in the same category, all of them sold as dehumidifiers. Which is why one average number is no use to anybody, and why the calculator below asks for your hours and your unit rate instead.

We would not pay for the 20 litre machine to sit in a heated flat: through the cap it is 10p an hour against 5.4p for the small compressor, and the only thing separating their labels was measured in a room nobody lives in. Two honest limits before you use the calculator. The watts are the maker's own declared figure, and where the maker does not publish them the calculator says so instead of inventing one, which happens on four of the ten machines here. And the monthly figure is the ceiling: once a machine reaches the humidity you asked it for, the compressor cycles off, and the real bill is lower by an amount that depends on your house and that nobody publishes.

Not one of the buying guides sitting in the top ten for this search mentions the following, and for a large share of the people searching it is the first thing that matters. There were 1.4 million homes in England with a damp problem in 2024, 5% of the stock, and the most common form of it was severe condensation, at 3%, ahead of penetrating damp at 2% and rising damp at 1%. The rate is 10% in privately rented homes, against 7% in social housing and 4% in owner-occupied homes. Those figures are the English Housing Survey, published on 29 January 2026.

The official guidance for rented housing providers, updated on 1 April 2026, is blunt about whose problem that is: “It is totally unreasonable to blame damp and mould in the home on 'lifestyle choices'… the fundamental cause of damp and mould will be due to building deficiencies, inadequate ventilation, inadequate heating and/or poor energy efficiency, not tenants' normal domestic activities.” That is the government's position, not ours, and it changes what a dehumidifier is for: it manages the symptom while somebody else fixes the cause.

That leaves the third number on the packaging, the coverage. It is the one most people buy on and the one that survives comparison worst, because machines declaring identical litres per day declare areas that look nothing like each other, and because the shops selling them cannot agree on what unit to size by in the first place.

The order is not by litres, for everything explained above. It is by who each one is for, and within each case what decides is what the maker publishes: tank, watts and decibels. Availability and models vary by country, so the buttons take you to your local Amazon store to check yours.

Between November and March nothing dries on a line in this country, and the search data shows what people do about it: drying clothes is one of the things typed alongside this category all winter. It is also the use where the compressor-or-desiccant decision stops being theoretical.

A desiccant returns warm, dry air, because the way it works is to soak up water and then drive it off with heat. That is why it dries a load fast and why it feels like it is heating the room a little. A compressor returns air at roughly room temperature; it still dries the washing, it just takes longer in a cold room, and in a really cold room it slows down sharply. Meaco, whose shop is the first organic result for this search, sells its machines on exactly that: “especially effective for drying laundry indoors”.

Two practical conditions that decide whether it works: hang the washing close to the machine with the door shut, because if the air spreads through the house the effect is diluted, and remember that laundry mode is the setting that draws the most power, so check the watts before leaving it on all night. If we were drying washing indoors we would take the desiccant over the bigger compressor, and the reason is on the same spec sheet: it puts out warm air and it still works at 1C, which is what a British utility room is in January.

A dehumidifier takes water out of the air. That is all it does. If the water in your wall is not coming from the air, the machine will run for years without fixing anything while the problem carries on spreading behind the paint.

The English Housing Survey splits the 1.4 million homes with damp into three kinds, and the split is the argument: severe condensation 3%, penetrating damp 2%, rising damp 1%. Condensation is the biggest single kind, so most of the time a dehumidifier is the right tool. But two of the three are not condensation at all, and for those it is the wrong tool entirely.

Telling them apart costs the price of a coffee and it is in this guide: measure the humidity of the room. Leave a meter in it for a couple of days and read it first thing in the morning, when the house is at its coldest. If the reading is low and you still have marks, bubbling paint or a tide line low on the wall, the water is coming in through a leak, a failed seal or up from the ground, and that is a repair, not an appliance. If the reading is high, then yes, the air has too much water in it and the machine has a job to do.