🗓 Updated September 17, 2026 · EcoBack editorial team
Start with the actual room conditions
A compressor dehumidifier condenses water on a cold coil; a desiccant model removes water using an adsorbent and regeneration process. Temperature and humidity affect performance, but neither a 10°C nor a 15°C room-temperature threshold proves which is the better buy.
The dew point tells you the temperature below which condensation can occur. It does not tell you the coil temperature, defrost time, extraction rate or cost of a particular appliance. At 10°C and 60% RH, the dew point is about 2.6°C: a coil below that value need not be below zero.
A cheap hygrometer gives you both numbers. The humidity reading is the one people guess wrong.
What to compare before buying
- Find each model’s operating range and extraction at the same temperature and humidity.
- Compare power together with water extraction; lower hourly watts do not guarantee a cheaper completed task.
- Check noise at the intended setting, drainage, tank access and placement instructions.
- If humidity remains high, investigate moisture sources and ventilation rather than assuming the device is too small.
Condition-matched manufacturer example · Compare a complete laundry session.
Illustrative running costs
These power bands and eight-hour runs are examples, not product tests, extraction comparisons or predictions of drying time. Use your own measured session and tariff.
At the Ofgem price cap for 1 October to 31 December 2026, the average electricity unit rate for Direct Debit in England, Scotland and Wales is 26.32p per kWh. This is not a Northern Ireland tariff; regional and plan rates vary. Scale the hours to your own run.
| Machine | Plate | Per hour | 8 hours | Cost (£) |
|---|---|---|---|---|
| Compressor dehumidifier, small | 200 W | 5.3p | 1.6 kWh | 0.42 |
| Compressor dehumidifier, typical | 300 W | 7.9p | 2.4 kWh | 0.63 |
| Desiccant dehumidifier, low setting | 330 W | 8.7p | 2.6 kWh | 0.69 |
| Desiccant dehumidifier, high setting | 650 W | 17.1p | 5.2 kWh | 1.37 |
Unit rate only, standing charge excluded — that is a daily fixed cost you pay whether the machine runs or not. There is no VAT on electricity from 1 October 2026 to 31 March 2027. Rate from Ofgem, read 2026-10-04. Your tariff may differ; the sum is watts ÷ 1000 × hours × your rate.
Common questions
Does a dew point above zero mean the compressor coil must freeze?
No. A coil must be below the dew point to condense water, but that can still be above freezing. The model and its control strategy matter.
Can this calculator pick the cheaper technology?
No. Compare condition-matched extraction, input power and complete-session cost for the exact models, within their operating ranges.
Sources and limits
Manufacturer example: MeacoDry Arete One 12L. No hands-on EcoBack tests. The dew-point approximation uses Magnus constants 17.62 and 243.12; it cannot model an appliance’s refrigeration cycle. Reviewed 4 October 2026.