To estimate the cost of a fan for eight hours per night, you need three pieces of information: the power consumed at the chosen setting, the number of hours of use and your price per kilowatt hour. The calculation is simple; the quality of the data makes all the difference.
The formula to keep
Consumption in kWh = power in watts ÷ 1,000 × duration in hours.
Cost in euros = consumption in kWh × price per kWh.
Eight hours per night for thirty nights represents 240 hours. A device that actually consumes 25 W for this entire duration therefore uses 25 ÷ 1000 × 240 = 6 kWh. It remains to multiply this result by the price applicable to your contract.
Three examples to understand, without announcing a current price
The powers below are pedagogical hypotheses, not the characteristics of an Oléa product. The price retained, 0.25 €/kWh, is also a calculation hypothesis: replace it with your actual price, all taxes included if you wish to estimate your expense.
- 10 W for 240 hours: 2.4 kWh, or €0.60 with this price hypothetical.
- 25 W for 240 hours: 6 kWh, or €1.50 with this hypothetical price.
- 50 W for 240 hours: 12 kWh, or €3 with this hypothetical price.
These amounts only concern the energy corresponding to the retained power. They do not include the purchase, installation or electrical subscription. They do not constitute a forecast of your bill.
Why the indicated power is not always enough
The nominal or maximum power does not necessarily describe consumption at low speed. If you primarily use the gentlest setting, look for a measured or documented value for that setting. Failing this, clearly announce that your estimate is based on maximum power and not on verified nighttime consumption.
Engine technology alone does not allow the expenditure to be quantified. Two devices can have different powers, like the same device with two speeds. Also check whether the advertised value concerns the motor alone or the motor and lighting assembly.
Lighting, timer and off-peak hours: useful adjustments
If the light works at the same time, calculate its consumption separately, then add the results. If a timer stops the fan after three hours, use three hours per night, not eight. Any standby time is calculated separately if its power is known.
With a peak/off-peak hours contract, distribute the hours in each range and apply each price separately. All night does not necessarily correspond to the off-peak hours of your contract. Do not use a price found online instead of the conditions appearing on your invoice.
Example with a three-hour timer
With the same assumptions of 25 W and a hypothetical electricity price of €0.25/kWh, using the fan for three hours a night over thirty nights gives: 25 ÷ 1 000 × 3 × 30 = 2.25 kWh, or 2.25 × 0.25 = €0.56 after rounding to the nearest cent. The calculation assumes that the fan operates at this power for all three hours; any standby consumption still needs to be added if its power is known.
Your calculation sheet in four lines
- Power used: ... W, from the instructions or an adapted measurement.
- Duration: ... hours per night × ... nights.
- Energy: power ÷ 1,000 × duration total.
- Variable expenditure: energy × real price per kWh.
For a fan connected to the ceiling, do not dismantle the installation to measure its consumption. Ask for the manufacturer's data or professional help for a suitable measurement.
Compare before choosing
In our Horizon ceiling fan collection, consult the sheet for the model and variant that interests you. If a power or measurement condition is missing, ask for clarification before converting an example into a personal estimate.
Sources: Australian Government, consumption and cost of appliances ; Virginia Cooperative Extension, calculation of power consumption. Generated ambient illustration.
