How much does it cost to use a fan? (formula + examples)
In Portugal, a fan is usually inexpensive to use: typical power consumption is in the range of 15 to 100 W (depending on the type and power).
1) The (very simple) formula
Cost (€) = (Watts ÷ 1000) × hours × price per kWh
Repsol gives a clear example: a 50 W appliance used 5 hours/day consumes 250 Wh (0.25 kWh) , and then you multiply that by the price per kWh.
2) Live example (step by step)
Let's assume a 50W fan running for 8 hours a day :
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Convert W → kW: 50 W ÷ 1000 = 0.05 kW
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Energy per day: 0.05 kW × 8 h = 0.40 kWh/day
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If you pay R$ 0.20/kWh : 0.40 × 0.20 = R$ 0.08/day
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In 30 days: 0.08 × 30 = R$ 2.40/month
3) 3 quick scenarios (typical values)
Use the price per kWh (€/kWh) from your contract/invoice to get the exact value.
Scenario A — 30 W desk fan, 6 hours/day
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Consumption/day: 30/1000=0.03 kW → 0.03×6= 0.18 kWh/day
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At €0.20/kWh → €0.036/day (~ €1.08/month )
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At €0.30/kWh → €0.054/day (~ €1.62/month )
Scenario B — 50 W pedestal/tower fan, 8 hours/day
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Consumption/day: 0.40 kWh/day
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At €0.20/kWh → €0.08/day (~ €2.40/month )
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At €0.30/kWh → €0.12/day (~ €3.60/month )
Scenario C — Ceiling fan (DC) 40 W, 10 h/day
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Consumption/day: 40/1000=0.04 kW → 0.04×10= 0.40 kWh/day
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At €0.20/kWh → €0.08/day (~ €2.40/month )
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At €0.30/kWh → €0.12/day (~ €3.60/month )
4) Important tip: compare with air conditioning.
Repsol uses the order of magnitude to help with comparisons: air conditioners can consume much more energy (e.g., up to ~2000 W, depending on the equipment), while fans typically consume much less.
FAQ
How much energy does a fan consume per hour?
It depends on the model, but typical specifications range between 15 and 100 W.
How do I calculate the monthly cost?
Calculate the cost per day and multiply by 30 (or by the actual number of days). Repsol demonstrates the method with an example of 50 W.