Dehumidifier Running Cost Calculator
Estimate how much a dehumidifier costs to run per day, month and winter season. Add wattage, hours, duty cycle, tariff, standing charge choice and water collection rate to see both cost and moisture removal value.
Appliance and Tariff Inputs
Estimated Running Cost
This estimate uses 300 W, 8 hours per day and a 65% duty cycle across 30 days.
Why Dehumidifier Costs Vary So Much
Two dehumidifiers with the same rated wattage can cost different amounts in the same home because the compressor or desiccant heater does not always run flat out. A humid laundry room can keep a compressor working for long periods. A bedroom that reaches the target humidity quickly may cycle off for much of the evening. The duty cycle field is included so you can model that on-and-off behaviour rather than treating the label wattage as a fixed cost for every minute.
The result is useful for damp rooms, drying clothes indoors, protecting stored items, managing condensation on windows and comparing appliance settings. It does not measure the cost of the damp problem itself. If you have mould, leaks, poor ventilation or structural damp, energy arithmetic should sit beside building repairs and health advice.
Choose the Right Input Style
Quick bill check
Use the label wattage, expected hours, the current p/kWh on your tariff and a duty cycle around 50% to 70% for a compressor model in normal use.
Laundry drying
Use the hours the appliance runs while clothes dry and a higher duty cycle if the room stays humid. Compare cost with a tumble dryer only if drying time and load size are similar.
Storage protection
For garages, boats, cellars and spare rooms, use lower hours or a humidity-controlled duty cycle. Add standing charge only where the electricity supply exists mainly for that space.
Formula and Method
average power in kW = rated watts / 1000 x duty cycle
daily kWh = average power in kW x hours per day
period kWh = daily kWh x days in period
energy cost = period kWh x electricity unit rate
standing charge cost = standing charge per day x days in period
total cost = energy cost + included standing charge cost
cost per litre = daily cost / litres collected per day
The calculator converts pence per kWh to pounds before adding costs. It keeps the standing charge optional because most households pay that charge whether or not a dehumidifier is used. Include it only when you are costing a separate supply, workshop, outbuilding or short-term property where the standing charge is part of the appliance decision.
How to Estimate Duty Cycle
If you do not have a plug-in energy monitor, start with a cautious assumption. Use 100% for a worst-case cost where the machine runs continuously. Use 60% to 70% for a compressor unit in a damp room that cycles but works hard. Use 30% to 50% for a room that reaches target humidity quickly. Desiccant dehumidifiers can use more power because they include a heater, but they may work better in colder rooms.
A plug-in meter gives the best reading. Measure one ordinary day and divide the kWh by the hours used. If a 300 W appliance runs for eight hours but the meter shows 1.4 kWh, the average power was 175 W, so the duty cycle was about 58%. You can then update the calculator with a value that reflects your room rather than the label.
Example Running Costs
| Use case | Inputs | Daily kWh | Approximate daily cost at 24.67p/kWh | Note |
|---|---|---|---|---|
| Bedroom condensation | 200 W, 4 hours, 50% duty | 0.40 kWh | 10p | Good for short evening use after showers or drying small items. |
| Laundry room | 300 W, 8 hours, 80% duty | 1.92 kWh | 47p | Often cheaper than a tumble dryer, but drying time may be longer. |
| Cold garage desiccant | 650 W, 6 hours, 70% duty | 2.73 kWh | 67p | Higher power, but may perform better at lower temperatures. |
| Whole flat damp spell | 300 W, 12 hours, 65% duty | 2.34 kWh | 58p | Useful as a short-term intervention while fixing ventilation or moisture sources. |
Reading the Result
The daily cost tells you whether a routine is affordable. The monthly cost helps with bills. The 120-day season cost is useful for autumn and winter condensation planning. Cost per litre is not a lab performance measure, but it can help compare settings. If the appliance collects very little water while still using energy, the room may already be dry enough, the filter may need cleaning, the target humidity may be too high, or the unit may be poorly placed.
Do not chase the lowest humidity possible. Very dry air can be uncomfortable and may affect wooden furniture or instruments. Many homes aim for a relative humidity range around 40% to 60%, but the right target depends on room use, ventilation and any medical advice. If damp is persistent, look for moisture sources such as drying clothes indoors without ventilation, blocked vents, leaks, cold bridges or inadequate heating.
FAQ
Should I include the standing charge?
Usually no. The standing charge is paid for the electricity supply even when the appliance is off. Include it only when costing a separate supply or a property where the appliance is the main reason for keeping electricity connected.
Is a dehumidifier cheaper than a tumble dryer?
Often for indoor air drying, but not always. Compare the full drying time, room heating effect, load size and how dry the clothes are at the end.
Why is my real cost different?
Your tariff, duty cycle, room temperature, humidity, filter condition, target setting and appliance type can all change energy use. A plug-in meter is the best way to refine the estimate.
Sources
- Ofgem. (2026). Energy price cap unit rates and standing charges. Office of Gas and Electricity Markets. Accessed 18 May 2026.
- Energy Saving Trust. (2026). Home appliances and energy use. Energy Saving Trust. Accessed 18 May 2026.
- NHS. (2025). Can damp and mould affect my health?. National Health Service. Accessed 18 May 2026.