Dehumidifier running cost calculator
What a dehumidifier costs per day, month and winter on your electricity tariff — plus how much water it will realistically remove in your room, which is often far less than the number on the box.
Why a "20-litre" dehumidifier won't remove 20 litres a day
Extraction capacity is measured under fixed test conditions, typically in a warm, very humid room (30 °C and 80% humidity is a common rating point). A UK bedroom on a winter morning might be 15 °C and 70%. In those conditions a compressor dehumidifier often removes only a quarter to a half of its rating, because there's less water in the air and its cold coil may need to stop and defrost.
The ENERGY STAR programme publishes the test conditions behind capacity ratings, which is a useful reminder that the headline litre figure is a comparison number, not a prediction for your home. Our calculator de-rates the stated capacity by temperature and humidity and shows a range.
Compressor or desiccant?
| Compressor | Desiccant | |
|---|---|---|
| Typical power | 150–300 W | 300–650 W |
| Best in | Heated rooms above ~15 °C | Cool or unheated rooms, garages, conservatories |
| Cold-room performance | Falls steeply; may defrost-cycle | Fairly steady |
| Side effect | Slight warming | Warms the room noticeably (a bonus in winter) |
| Noise | Compressor hum | Fan only, usually quieter |
Getting the most from a dehumidifier
- Close the door. Otherwise it tries to dry the whole house and the outdoors coming in through vents.
- Run it when the moisture is produced — while laundry dries or overnight in a bedroom — rather than at random.
- Set a target around 50–55%. Lower targets cost more and add little protection.
- Keep it away from walls and curtains so air can circulate, and empty or drain it regularly.
- Measure the result: note the litres collected and, with a plug-in energy meter, the kWh used over the same week. That tells you your real cost per litre.
Is a dehumidifier the right fix?
It treats the symptom — moisture in the air — and can work well, especially for laundry drying or a single problem room. It won't fix rain penetration, leaks, failed double-glazing seals or a wall so cold it condenses at any normal humidity. The full assessment compares a dehumidifier against ventilation, heating and other changes for your room, including how they interact.