How we choose
Airsum starts with your room and your problem, not a product list. This page sets out the rules we use so you can check them.
What we do and don't do
- We don't test products ourselves. Every specification on the site comes from a linked source, shown on each product page.
- If we can't find a figure from a source we trust, we leave it blank rather than guess.
- We don't sell or stock anything. Links go to the maker or a retailer, and some earn us a commission (see affiliate disclosure). Commission is not used to rank or pick products.
Dehumidifier sizing
The sizer gives your room points, adds points for conditions that make a room harder to dry, then maps the total to a capacity band in litres per day.
| Floor area | Points |
|---|---|
| Up to 15 m² | 1 |
| 15 to 30 m² | 2 |
| 30 to 60 m² | 3 |
| Over 60 m² | 4 |
Then add one point each for: drying laundry indoors, heavy damp, four or more people in the home, and a space that is unheated or usually below about 12°C.
| Total points | Suggested capacity |
|---|---|
| 1 | 5 to 10 L/day |
| 2 | 10 to 12 L/day |
| 3 | 12 to 16 L/day |
| 4 | 16 to 20 L/day |
| 5 or more | 20 L/day or more, or two units |
This is our own rule of thumb, version 0. It is a guide, not a guarantee, and we'll revise it if the evidence says we should.
Type
- Heated room: compressor or hybrid.
- Partly heated: compressor, desiccant or hybrid.
- Cold space: desiccant or hybrid.
Read more in compressor vs desiccant.
The three picks
- Best fit: rated capacity closest to the middle of your band.
- Cheapest to run: lowest running cost per litre, using the current price cap rate of 26.32p/kWh (October 2026 price cap, as quoted by Which?) and the unit's listed power.
- Quietest: lowest listed noise level.
Only units that are suitable for your type and band are considered. If the same unit wins more than one pick, you'll see it once.
Air purifier sizing
Required clean air delivery rate (CADR, in m³/h) = room volume × air changes per hour (ACH).
- General use: 3 ACH
- Allergies, pets or smoke: 5 ACH
- Quiet bedroom: 2 ACH
Maker claims for room size often use fewer air changes than independent standards, so we compare on CADR where it's published. See room size and CADR.
We label filters carefully: H13 or H14 only where a source confirms it, "not confirmed" where a listing says "HEPA" without a grade, and "Not a True HEPA filter" where the product doesn't claim one.
Damp that isn't a dehumidifier problem
If you have wet patches, leaks or mould that keeps coming back, a dehumidifier may only treat the symptom. The sizer says so when you tick those boxes. See when damp isn't a dehumidifier problem.
Spotted an error?
Tell us at info@airsum.co.uk and we'll check it against the source.