What the litre rating on a dehumidifier really means, and how 10L, 12L, 20L and 25L models compare on capacity, size, noise, tank and running cost in UK homes.
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A 10L or 12L dehumidifier suits a single room, a flat or a small house with occasional condensation — the two are often near-identical, so 12L is usually the better buy. Step up to 20L for a family home, daily indoor laundry or condensation in several rooms, and to 25L only for large homes or heavy laundry. The litre figure is daily extraction in warm test conditions, not tank size.
The number on the front of a dehumidifier box — 10L, 12L, 20L, 25L — is the single most quoted spec, and the most misunderstood. Here’s what it actually tells you, and how to pick between the common capacity classes. If you’d rather start from your own home, the size calculator suggests a class and estimates the running cost.
The litre figure is how much water the unit can remove in 24 hours in standard test conditions. For compressor models that’s usually 30°C and 80% relative humidity — a warm, sticky summer day, not a British living room in winter.
Two consequences:
| 10L | 12L | 20L | 25L | |
|---|---|---|---|---|
| Typical use | Single room, studio, 1-bed flat | Bedroom, 1–2 bed flat, small house | 3-bed house, daily laundry, several damp rooms | Large homes, heavy laundry, serious damp |
| Typical power | 150–200W | 150–250W | 300–500W | 350–550W |
| Typical tank | 2–3L | 2–3L | 3–5L | 4–6L |
| Weight | Lighter | Similar to 10L | Noticeably heavier; castors common | Heaviest |
| Noise | Quietest | Similar to 10L | Louder at full power | Loudest at full power |
| Laundry | 1–2 small loads a week | Occasional loads | Regular loads | Daily loads for a large household |
These are typical ranges across the market, not specifications for any particular model — always check the listing.
Many 10L and 12L models share the same body and differ mainly in the compressor and fan. The price gap is often small, so 12L is usually the better buy — the extra headroom helps in cooler rooms and with occasional laundry. Choose 10L if it’s genuinely for one small room and you want the quietest, lightest option.
This is the decision most people face. Choose 12L if:
Choose 20L if:
A 20L unit runs harder per hour but reaches your target humidity sooner and then cycles off — so running costs per litre removed are closer than the wattage suggests. Our running costs guide has a calculator.
The jump from 20L to 25L is incremental. It makes sense for large homes, households drying several loads a day, or serious damp after a leak has been fixed. For most homes, a 20L unit used with the doors closed in the worst room does the same job.
Links go to Amazon's current range for each class, so you can compare features and prices yourself.
Rooms and flats
Family homes and laundry
Large homes only
How we choose: these are types of product matched to the criteria in this guide, not individually tested models. Check current specifications and reviews before you buy.
Our dehumidifier size calculator asks about your home, temperature, laundry and how bad the problem is, and suggests a starting class. For features beyond capacity, see how to choose a dehumidifier; if laundry is the main job, see using a dehumidifier to dry clothes.
It's the maximum amount of water the unit can remove from the air in 24 hours, measured in warm, humid test conditions (often 30°C and 80% humidity). It is not the size of the water tank, which is usually 2–5 litres. In a cooler UK home, real extraction is much lower than the headline figure.
For a small house or a two-bedroom home with mild to moderate condensation, often yes — especially if you move it to the worst room. For a three-bedroom house with daily indoor laundry or damp in several rooms, a 20L model is the safer choice.
It will work, and it will reach your target humidity quickly before cycling off. The downsides are size, weight, cost and noise at full power. Unless you also want it for laundry or the rest of the home, a 10–12L model with a sleep mode is the better bedroom choice.
It draws more power per hour — often 300–500W against 150–250W — but it also removes water faster, so it reaches the target humidity sooner and switches off. Per litre removed, the difference is smaller than the wattage suggests.
Only for large homes, serious damp or heavy laundry for a big household. The step from 20L to 25L adds less than the step from 12L to 20L, and 25L units are usually the heaviest and largest.
A plain-English guide to choosing a dehumidifier for a UK home — compressor or desiccant, the features worth paying for, and the marketing claims to ignore.
How to dry washing indoors with a dehumidifier without damp, how long it takes, the set-up that works best, and what size and features to look for.
How desiccant and compressor dehumidifiers work, why room temperature matters so much in UK homes, and which type to buy for each room.
