What Size Dehumidifier Do I Need? UK Guide by Room and Damp Level

Quick answer: most UK homes need a 10L to 12L dehumidifier for one damp room or a small flat, and a 20L model for a three-bedroom house or for drying washing indoors most days. Go up one size for severe damp, and choose a desiccant model for rooms that stay below about 10°C, such as unheated garages.

Last updated 26 October 2026 · Facts checked by Abdul Aziz

This guide sizes a dehumidifier the way the problem actually works: by how much water your household puts into the air, how much a machine really removes in a normal UK room, and how cold the room gets. Every model mentioned is from our dehumidifiers and air treatment range, with specs taken from the manufacturers' listings.

What size dehumidifier do I need for my room or home?

Size by the damp problem and household first, then check the room is warm enough for the type you pick. Room area matters less than most charts suggest, because makers' coverage claims vary widely (see below).

Your situation	Label size to buy	Type	Why
Wardrobe, cupboard, drawer, car or caravan locker	Non-electric moisture absorber	Crystal absorber	Small, enclosed space; no power or noise needed
One bedroom or box room, condensation on the window most mornings	10L to 12L	Compressor	Two people breathing overnight plus a cold window is a small, steady load
One- or two-bedroom flat, occasional indoor drying	12L	Compressor	Covers cooking, showers and a load or two of washing a week
Three-bedroom house, or washing dried indoors most days	20L	Compressor	Household moisture can pass 20 litres a day with indoor drying
Four bedrooms or more, visible mould, damp walls, or a basement	20L to 25L, or one per floor	Compressor	Large, persistent load; a bigger tank and continuous drainage help
Room that regularly sits below about 10°C (garage, shed, unheated spare room)	Any size	Desiccant	Small compressor units lose output and spend time defrosting in the cold

Sizing bands reflect the consensus in UK retailer and manufacturer guidance (10L to 12L for a small damp room, 20L or more for a whole house or heavy laundry), adjusted for the real-world output and moisture figures below. Temperature thresholds: Meaco guidance on compressor and desiccant dehumidifiers, accessed 26 October 2026.

What does "10L", "12L" or "20L" actually mean?

It is the most water the machine can pull out in 24 hours under test conditions, not the size of its water tank. The test conditions are hot and very humid, so in a normal UK room you get much less.

Most UK dehumidifiers are rated at 30°C and 80% relative humidity, which is closer to a tropical summer than a British winter. Meaco is one of the few makers that also publishes extraction at 20°C and 60% relative humidity, a typical heated UK room. Its own figures show the gap clearly:

Meaco model (maker's data)	Extraction at 30°C / 80% RH	Extraction at 20°C / 60% RH	Real-world share of label
Arete One 10L	10.42 litres a day	4.34 litres a day	42%
Arete One 12L	12.18 litres a day	5.23 litres a day	43%
MeacoDry ABC 12L (high fan)	12.1 litres a day	5.18 litres a day	43%
20L Low Energy	20.38 litres a day	8.48 litres a day	42%
Arete Two 25L	25.25 litres a day	10.85 litres a day	43%

Source: Meaco product specification tables, accessed 26 October 2026.

Rule of thumb: in a heated room at around 20°C and 60% humidity, expect roughly 40% of the label figure. A 12L unit removes about 5 litres a day there and a 20L unit about 8 litres. It extracts more when the air is damper, and less once the room reaches your target humidity, because the humidistat switches the compressor off. This is why a 20L machine is not "too much" for a family house: in winter it will often be doing 8 litres of real work.

How much moisture does a UK household put into the air?

About 12 litres a day for an average household, rising to over 20 litres when clothes are dried indoors, according to South Kesteven District Council. Indoor drying is the single biggest variable.

Activity	Moisture added to the air	Source
Breathing while asleep	0.3 litres	Mid Sussex District Council
Breathing while awake	0.85 litres	Mid Sussex District Council
Cooking	Up to 3 litres a day	Gosport Borough Council; Mid Sussex District Council
Showers and baths	1.5 litres per person	Gosport Borough Council
Drying one load of washing indoors	About 2 litres (average load) to 5 litres	Glasgow School of Art MEARU research, 2012; Gosport Borough Council
Whole household, per day	About 12 litres; over 20 litres with indoor drying	South Kesteven District Council

Council damp and condensation guidance accessed 26 October 2026. Figures are estimates and vary with household size and habits.

Ventilation, extractor fans and opening windows remove part of this, so a dehumidifier does not need to match the full total. It needs to remove the excess that is currently ending up on windows, walls and fabrics.

How do I work out the size for my home? Four worked examples

Add up your main moisture sources, compare them with the real-world output (about 40% of the label), and pick the size that covers the excess without running flat out all day.

1. Couple in a one-bedroom flat, washing dried indoors twice a week, condensation on the bedroom window. Breathing, two showers and cooking add roughly 5 to 8 litres a day, rising to about 13 on washing days. Ventilation handles part of it. A 12L unit (about 5 litres a day of real extraction) placed in the bedroom overnight and by the airer on washing days fits.
2. Family of four in a three-bedroom semi, a load of washing dried indoors most days. Breathing adds about 4.6 litres, showers about 6, cooking up to 3 and washing 2 to 5, so the total is around 16 to 19 litres and can pass 20. Choose a 20L unit (about 8 litres a day of real extraction) with a large tank or continuous drainage, and run it in laundry mode near the airer.
3. One damp bedroom in an otherwise dry house. The load is mostly breathing overnight plus a cold outside wall. A quiet 10L unit on its humidistat is enough. Fix any ventilation problem too, such as a blocked trickle vent.
4. Single garage used as a workshop, 5 to 10°C in winter. Size matters less than type here. Choose a desiccant dehumidifier, which Meaco states works down to about 1°C, because small compressor models lose much of their output below about 15°C.

Compressor or desiccant: which type does my room need?

Compressor for heated living spaces; desiccant for cold spaces. Compressor models are cheaper to run in a warm room, while desiccant models keep working in the cold and give off a little warmth.

• Compressor (refrigerant): cools a coil so moisture condenses on it. Meaco advises that small 6L to 12L compressor units are no longer the right choice below about 15°C, while some larger 20L and 25L models are engineered to stay efficient down to about 10°C. Below that they spend more time defrosting.
• Desiccant: absorbs moisture into a material that is dried by an internal heater, so output stays steadier as the temperature drops. They use more electricity, which partly turns into heat in the room.
• Check the operating range: for example, the Wood's MDK11 lists 5°C to 35°C. That is the range it will run in, not the range in which it reaches its label output.

If a room is cold because it is not heated at all, warming it a little also helps a compressor unit work. Our heater sizing guide covers that side.

Do manufacturers' room-size claims help?

Not much on their own. The stated coverage on the models we stock ranges from 20m² for a 12L unit to 50m² for a 10L unit, so a smaller machine can claim a bigger room. Use these claims as a rough upper limit and size by moisture instead.

Model (maker's figures)	Label extraction	Stated coverage	Tank	Power	Noise	Continuous drainage	Best for
Meaco Dry Arete One 10L	10L/day	1 to 2 bedroom homes and flats	2.5L, side access	151W (at 20°C, 60% RH)	From 35dB	Yes, hose adapter	Bedrooms and flats; adds H13 HEPA filtration
Wood's MDK11 10L	10L/day	Up to 50m²	1.8L	210W	46dB	Yes, external hose	Compact flats and utility rooms; 5°C to 35°C range
Duux Bora 12L	12L/day	Up to 30m²	1.7L	160W	42 to 56dB	Yes, hose included	Lowest power 12L here; no app
Pro Breeze 12L Smart	12L/day	Not stated	1.8L	200W	Not stated	Not stated	App, Alexa and Google Home control
Pro Breeze OmniDry 12L	12L/day	Up to 20m²	2.0L	Not stated	36dBA (Sleep mode)	Not stated	Bedrooms; Auto mode holds 40 to 60% RH
Duux Bora Smart 20L	20L/day	Up to 40m²	4L	20W to 260W	36 to 42dB, Quiet Mark	Yes, hose	Family homes; app control, laundry mode
Pro Breeze 20L Premium	20L/day	Up to 30m²	5.5L	See product page	42dBA or less	Not stated	Heavy laundry drying; largest tank here
Absodry Moisture Absorber Bundle	Non-electric	Spaces up to 50m³	Built-in reservoir	None	Silent	No	Wardrobes, cupboards and storage areas

Specs from manufacturer listings on each product page. "Not stated" means the maker's listing does not give the figure.

How often will I need to empty the tank?

Divide the real-world output by the tank size. In a damp heated room, a 12L unit removing about 5 litres a day with a 1.7L to 2L tank fills it two or three times a day if it runs continuously.

• A 20L unit removing about 8 litres a day fills a 4L tank about twice a day and a 5.5L tank about one and a half times.
• Every model in the table stops automatically when the tank is full, so it will not overflow, but it stops drying the room until you empty it.
• If you are out all day or the damp is heavy, choose a model with continuous drainage and run the hose to a sink, shower tray or floor drain lower than the outlet.
• Tank-emptying frequency drops as the room dries, because the humidistat cuts the running time.

How much does a dehumidifier cost to run?

Between about 4p and 7p an hour for the compressor models above, at the Ofgem price cap of 26.32p per kWh for October to December 2026. Eight hours a day costs roughly 32p to 55p.

Model	Listed power	Cost per hour	Cost for 8 hours
Meaco Dry Arete One 10L	151W	4.0p	32p
Duux Bora 12L	160W	4.2p	34p
Pro Breeze 12L Smart	200W	5.3p	42p
Wood's MDK11 10L	210W	5.5p	44p
Duux Bora Smart 20L (maximum)	260W	6.8p	55p

Cost = listed watts ÷ 1,000 × 26.32p. Real costs are usually lower, because the compressor cycles off once the target humidity is reached. Rate: Ofgem price cap for 1 October to 31 December 2026.

What humidity should I set it to?

Aim for 40% to 60% relative humidity. UK council damp guidance warns that mould is likely when indoor humidity stays at 70% or more for long periods, and some councils put the warning level at a consistent 60%.

Set the humidistat to about 50% to 55% in winter. Lower settings make the machine run longer for little benefit. A cheap hygrometer in the problem room tells you whether the level is holding, and cold corners and outside walls can be damper than the room reading suggests, so keep furniture a few centimetres off outside walls.

How to choose the right dehumidifier, step by step

1. Measure the problem. Note where condensation or mould appears and check humidity with a hygrometer for a few days.
2. Count your moisture sources. Use the table above: people, showers, cooking and, above all, indoor drying.
3. Convert the label to real output. Take about 40% of the label figure for a heated room at 20°C.
4. Pick the size. 10L to 12L for one room or a small flat, 20L for a family house or daily indoor drying, and one size up if you see mould.
5. Check the temperature. If the room sits below about 10°C to 15°C, choose desiccant.
6. Check tank size and drainage. Continuous drainage saves emptying if the unit runs while you are out.
7. Check noise for bedrooms. Look for 36dB to 42dB or a sleep mode.
8. Keep ventilating. A dehumidifier works alongside extractor fans and trickle vents, not instead of them.

Frequently asked questions

Is a 10L dehumidifier big enough for a 3 bedroom house?

Only if the house has a light damp load and no regular indoor drying. In a heated room a 10L unit removes about 4 litres a day, while a typical household adds around 12 litres, or over 20 with washing dried indoors. For a family in a three-bedroom house, a 20L model is the safer choice.

Can a dehumidifier be too big for a room?

Not in a harmful way. A larger unit reaches the target humidity faster and then its humidistat switches the compressor off, so it does not over-dry the room. The downsides are a bigger, heavier machine, more fan noise at full speed and a slightly higher cost per hour while it runs.

Should I get a 12L or 20L dehumidifier?

Choose 12L for one room or a one- to two-bedroom flat with occasional indoor drying. Choose 20L for a three-bedroom house, a family that dries washing indoors most days, or visible mould. In a typical heated room a 12L unit removes about 5 litres a day and a 20L about 8 litres.

How long should I run a dehumidifier each day?

Let the humidistat decide rather than a fixed number of hours. Set it to about 50% to 55% and leave it on in the problem room. It will run most when you are cooking, showering or drying washing, then cycle off. For laundry, run it beside the airer with doors closed until the clothes are dry.

What size dehumidifier do I need for drying clothes indoors?

Go one size above what the room alone needs. A load of washing releases about 2 to 5 litres of water as it dries, so a 12L unit suits a flat drying a load or two a week, and a 20L unit with laundry mode suits daily drying. Close the door and place the unit close to the airer.

Does a dehumidifier work in a cold room or garage?

A compressor dehumidifier struggles in the cold: Meaco advises small compressor units are not the right choice below about 15°C because they lose output and spend time defrosting. For a garage, shed or unheated room below about 10°C, choose a desiccant dehumidifier, which keeps working down to about 1°C.

Ready to choose? Compare every model in our dehumidifiers and air treatment collection, or browse the wider cooling, air treatment and heating range.

Sources: Meaco product specification tables and guidance on compressor and desiccant dehumidifiers (meaco.com, accessed 26 October 2026); Mackintosh Environmental Architecture Research Unit, Glasgow School of Art, indoor laundry drying research (2012); South Kesteven District Council, Mid Sussex District Council and Gosport Borough Council damp and condensation guidance (accessed 26 October 2026); Epping Forest District Council damp and mould guidance (accessed 26 October 2026); Ofgem energy price cap, 1 October to 31 December 2026 (26.32p per kWh); product specs from manufacturer listings.