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What size dehumidifier do you need?

Choose capacity around temperature, moisture workload and available space rather than a room-area promise.

By Dehumidifier UK · Updated 6 October 2026 · Sources linked below

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Our answer

For a heated small flat with modest moisture, start by comparing the Arete Two 12L. For more frequent laundry or a larger moisture workload, compare the 20L. For a genuinely cool suitable room, consider desiccant output at low temperatures. These are starting points, not a square-metre guarantee.

Why litres per day can mislead

A compressor’s headline rating is usually established in warm, humid test conditions. Meaco’s 12L is stated at 11.99 L/day at 30°C/80% RH, but 5.40 L/day at 20°C/60% and 1.97 at 10°C/60%. A home rarely stays at the headline condition. A machine also collects less as it lowers the room’s humidity.

Useful checks before buying

  • Measure the room’s temperature and RH during the period you need extraction.
  • Identify whether the workload is background humidity, one laundry rack or repeated loads.
  • Measure the machine footprint plus the clearance required by its exact manual.
  • Check tank size, access for emptying and whether a gravity drain is possible.
  • Compare output and power at the same temperature/RH rather than match headline tank or capacity numbers.

A practical starting shortlist

NeedStarting comparisonReason
Heated bedroom or small flatArete Two 12LSmaller body, lower low-mode noise and published 20°C output.
More laundry in a heated roomArete Two 20L8.50 versus 5.40 L/day at 20°C/60% RH and a larger tank.
Cool indoor utility spaceDD8L Pro / DD128 / DD1 SimpleDesiccant alternatives; compare extraction with higher power and manual restrictions.

Bigger is a trade-off

A larger appliance can provide more extraction and airflow, but it costs more space and may be louder on its strongest setting. Its increased output does not prove it uses less electricity per completed load. Compare the 12L and 20L directly before choosing the larger body by default.

When size is not the main issue

A blocked filter, poor air circulation, a hose that runs uphill or a target above the actual RH can prevent useful operation. Leaks and faulty building ventilation need their own remedy. If your existing machine is underperforming, use the troubleshooting sequence before replacing it.

Sources and evidence

  1. Meaco Arete Two 12L specifications and extraction table
  2. Meaco Arete Two 20L specifications and extraction table
  3. Meaco DD8L Pro specifications and mode-specific extraction
  4. EcoAir DD128 product specifications
  5. EcoAir DD1 Simple MK3 product specifications
  6. GOV.UK: addressing damp and mould in homes

Sources checked 6 October 2026. Manufacturer specifications are claims under their stated conditions; they are not our household measurements.