Before you begin
What this tool needs
Measure the area of the connected space the machine will actually serve.
Choose severe only for persistent moisture, not a single cold morning.
Reading the answer
What your result means
The litres-per-day figure is the size of machine to buy, not the water you should expect it to collect in an Irish winter.
Compressor units are efficient in heated rooms; desiccant machines keep working in genuinely cold spaces.
Boundaries
Assumptions and limitations
Working assumptions
- The size is rounded up to the 8, 10, 12, 16, 20, 25 or 30 L/day machines actually sold.
- Running cost is estimated at 0.2 kWh an hour for a compressor and 0.6 kWh an hour for a desiccant.
Where to be careful
- A dehumidifier does not repair leaks, rising damp, failed gutters or thermal bridges.
- Persistent mould needs the moisture source addressed as well as cleaning and ventilation.
Common questions
Questions about this tool
Why might a 20 L machine collect much less than 20 litres?
The rating is normally measured in warm, very humid laboratory air. Extraction falls sharply in cooler real rooms.
What indoor humidity should I aim for?
About 50–60% relative humidity is a practical target. Sustained readings above roughly 70% support mould growth.