Buying guide
12L vs 20L Dehumidifier
Choose a 12-litre class dehumidifier for a smaller heated space and a moderate moisture problem. Move towards a 20-litre class when the area, number of rooms, condensation severity or indoor-laundry load increases.
Do not choose from property size alone: a cold room can change the useful extraction rate, and two machines with the same headline capacity can differ in airflow, noise and control.
Check which dehumidifier capacity suits my home
What 12L and 20L describe
The label describes a nominal maximum extraction rate in litres per 24 hours under the manufacturer's stated test conditions. It does not describe the tank capacity.
It also does not mean a 20L model will put 20 litres in its tank during an ordinary day in a UK home.
Warmer air can hold more water vapour, and a wetter test condition gives the machine more moisture to remove.
Meaco's published extraction-rate table illustrates this clearly: both its 12L and 20L compressor models remove less water at 20°C and 60% relative humidity than at the warmer and wetter rating condition.
Compare like with like wherever manufacturers publish more than one test point.
| Factor | 12L class | 20L class |
|---|---|---|
| Likely starting use | One room or smaller heated home with mild to moderate moisture | Larger area, several affected rooms, heavier condensation or regular laundry |
| Extraction headroom | Lower | Higher |
| Physical size and weight | Often smaller and lighter | Often larger and heavier |
| Noise | Can be quieter, but check the exact mode and figure | Larger airflow may be more noticeable; model design matters |
| Input power | Often lower for comparable compressor designs | Often higher while actively dehumidifying |
| Tank | Model-specific and unrelated to the 12L or 20L label | Model-specific and unrelated to the 12L or 20L label |
When 12L may be enough
A 12L model is a reasonable shortlist starting point when most of these statements are true:
- The space is normally heated rather than cold.
- The problem is mainly one room or a compact flat.
- Condensation is occasional or moderate rather than persistent throughout the property.
- Indoor laundry is occasional rather than several loads each week.
- Lower weight, smaller dimensions or quieter operation matters.
- You are willing to run the machine consistently and allow useful air movement.
A smaller machine does not have to be ineffective. If it reaches and maintains the selected humidity, extra headline capacity may offer little benefit for that use.
Check the humidistat, fan behaviour and the maker's operating instructions rather than judging by litres alone.
When 20L is more appropriate
The 20L class deserves priority when several rooms are affected, condensation is regular, more people live in the property, or laundry is frequently dried indoors.
It can also provide useful recovery speed after showers, cooking or a wet load has raised humidity, provided air can reach the unit.
A larger model cannot fix restricted circulation. If the machine sits behind furniture, doors stay closed or moisture is generated on another floor, the nominal capacity will not remove those barriers.
Nor can it repair a leak, bridge a failed damp-proof detail or replace required ventilation.
Laundry changes the comparison
Wet clothes release water into the room as they dry. A larger compressor model can offer more extraction and airflow headroom, which is useful for repeated loads in a heated room.
But check the complete arrangement: place washing with space between items, direct dry airflow across rather than into fabric, keep the machine's clearances, and prevent new outdoor moisture entering while it operates.
A laundry programme is usually a control strategy, not a different extraction technology. It may run the fan harder or use a lower humidity target. Read the manual to learn how that mode behaves and whether it stops automatically.
Continue with the dehumidifier laundry guide.
Noise, wattage and physical size
Do not assume every 12L machine is quiet or every 20L machine is noisy. Compare sound figures recorded for the specific fan settings and remember that compressor cycling changes the character of the sound.
For a bedroom, the lowest usable setting can be more relevant than the headline maximum.
Similarly, a 20L machine does not necessarily draw maximum power for 24 hours. A compressor and fan draw power while actively working; once the target humidity is reached, control behaviour varies by model.
Use the published input wattage as an upper-style calculation for the hours entered, then measure a typical week if you need a closer figure. Estimate the running cost with your own tariff.
Make the decision in the right order
First decide whether the space and temperature favour compressor or desiccant technology. Then choose an extraction class using moisture load, area and desired recovery speed. Finally compare noise, drainage, tank access, controls and verified dimensions.
The SetupSelect dehumidifier finder follows that order.
For a fuller explanation of nominal capacity, read what size dehumidifier do I need?, and for cold spaces read compressor vs desiccant.
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