What Size Dehumidifier Do I Need? A Guide to Tank Size and Extraction Rates.

Picking the right dehumidifier doesn't have to be complicated. Whether you're battling condensation on your windows, drying laundry indoors, or dealing with a damp corner of the house, this guide will help you choose the right size — and the right tank — for your home.

Extraction Rate vs Tank Size: What's the Difference?

This is the bit that trips most people up. When a dehumidifier is listed as "12L" or "20L," that number refers to how much moisture it can extract from the air in 24 hours — not the size of the water tank. The physical tank is much smaller, typically between 2 and 4.8 litres. So a 12L dehumidifier with a 2L tank might need emptying once or twice a day if conditions are very damp. 

What Causes Humidity in UK Homes?

In the UK, damp air is a year-round issue. Everyday activities build up moisture quickly — cooking, showering, drying clothes indoors, even breathing all add humidity to the air.

Older homes with poor insulation or ventilation tend to suffer more, especially during autumn and winter when cold surfaces cause condensation. The ideal indoor humidity level sits between 45–55%. Below that, the air feels dry and uncomfortable. Above it, you risk mould growth, condensation, and musty smells.

Which Size Dehumidifier Do I Need?

Small rooms or 1–2 bedroom homes: The Devola DV12L is a great starting point. It's quiet, energy-efficient at around 5p per hour to run, and its 2L tank is easy to empty. Perfect for bedrooms, studies, and bathrooms.

Medium homes or persistent damp: Step up to the Devola DV20L, which offers a larger 4L tank and greater extraction power — ideal for 2–4 bedroom homes with higher moisture levels.

Larger homes or severe damp: The Devola DV25L is built for bigger spaces and wetter conditions. Alternatively, the MeacoDry Arete Two 20L is an excellent option with a 4.8L tank, smart app control, and a HEPA filter for cleaner air alongside moisture removal.

What Is Continuous Drainage and Do I Need It?

All dehumidifiers have a tank that fills up and needs emptying. But if you want to run the unit without interruption — say, in a utility room or overnight — continuous drainage is a brilliant feature. It works by attaching a hose to the unit, which then directs water straight to a drain or bucket, bypassing the tank entirely. Models like the Devola DV20L and DV25L support this, meaning you can leave them running without worrying about them switching off when the tank fills up.

Cold Spaces: Cellars, Garages, and Caravans

Here's something worth knowing: standard compressor dehumidifiers work best above around 5°C. In colder spaces like a garage, cellar, or caravan — especially in winter — they can struggle or stop working efficiently altogether.

For these environments, a desiccant dehumidifier is a better choice. Rather than relying on refrigerated coils, desiccant models use a moisture-absorbing material that works effectively even at temperatures as low as 1°C. They also gently warm the air as they operate, which is a bonus in cold outbuildings.

The Meaco DD8L is a popular and well-regarded option for exactly this kind of use. It has a 2L tank, supports continuous drainage, and is suitable for boats, caravans, holiday homes, and garages. It's lightweight, quiet, and cheap to run — a smart pick for any unheated space.

Ready to Find the Right Model?

Whether you need a compact unit for a bedroom or a powerful model for the whole house, there's a dehumidifier to suit every home and budget. Shop dehumidifiers now at Aircon Centre and find the perfect match for your space.