The short answer
For an uninterrupted constant draw, a dehumidifier’s 24-hour cost is input watts ÷ 1,000 × 24 × your tariff. Being enabled for 24 hours does not prove it draws full power all day. A complete-day kWh measurement includes the cycling captured in that sample and should not be reduced again.
Continuous input and 24 hours enabled are different
For a constant electrical draw, daily cost = input watts ÷ 1,000 × 24 × your price per kWh. An illustrative 250 W draw continuing for all 24 hours uses 6 kWh. At £0.28/kWh, it costs £1.68.
Leaving the appliance enabled all day does not prove it draws that input continuously. ENERGY STAR explains that a humidistat can cycle a dehumidifier to maintain the selected humidity level.
A full-input table is a scenario
The following figures assume an uninterrupted draw at each stated wattage. These are illustrative power scenarios, not measurements of named products or averages for a particular dehumidifier type.
| Constant electrical input | Energy over 24 hours | Cost at £0.28/kWh |
|---|---|---|
| 200 W | 4.8 kWh | £1.34 |
| 250 W | 6 kWh | £1.68 |
| 500 W | 12 kWh | £3.36 |
| 700 W | 16.8 kWh | £4.70 |
Enter your mode’s electrical input and 24 hours in the dehumidifier calculator to reproduce a full-input scenario. Do not enter litres or pints per day in the power field; those units describe water removal.
A measured complete day includes cycling
Suppose an illustrative appliance-only sample records 3.6 kWh across two complete days. Its daily average is 1.8 kWh, costing £0.50 per sampled day at £0.28/kWh when rounded for display.
In measured mode, enter 3.6 kWh and two complete measurement days. For 30 comparable use days, the unrounded projection is 54 kWh, costing £15.12. Multiplying the displayed rounded daily £0.50 by 30 would lose precision.
The sample already includes cycling and any idle electricity captured during the measurement. An extra assumed “50% duty cycle” would reduce the same energy a second time.
Record the conditions behind the reading
Temperature, moisture load, selected target and mode can change how a dehumidifier operates. ENERGY STAR advises checking the product’s suitability for lower operating temperatures.
Note the room conditions and whether the sample covers initial drying or ordinary maintenance. A measurement while a particularly wet space is first being dried may not represent later days. Conversely, a dry period can understate the energy required during a wetter one.
If the conditions you expect are different, take another suitable sample rather than treating the first daily average as a permanent product property.
Compare useful work as well as the bill
Electricity cost alone does not establish how effectively two appliances remove moisture in a given room. Read compressor versus desiccant dehumidifier costs for a comparison that includes conditions and water removed.
Choose the number of use days for your intended period. The calculator does not assume a dehumidifier needs year-round operation or determine how long yours should remain enabled.