Electricity consumption: watts to kWh, then kWh to €
If you’ve ever wondered how much a device costs to run, this electricity consumption calculator helps you turn a power value in watts (W) into an energy value in kilowatt-hours (kWh), and then into a cost in euros (€). Many appliances display power in watts (for example: a heater, a gaming PC, a TV, an oven, or a washing machine). Your electricity bill, however, is billed in kWh — so you need a simple conversion to estimate the real impact on your monthly or yearly budget.
The key idea is that power (watts) is not the same as energy (kWh). Power tells you “how fast” a device uses electricity, while energy depends on both power and time. To convert watts into kWh, you first convert watts to kilowatts by dividing by 1000, then multiply by the number of hours: kWh = (W ÷ 1000) × hours. For example, a 1000 W device (1 kW) running for 2 hours uses 2 kWh. If your tariff is €0.25/kWh, the cost is 2 × 0.25 = €0.50 for that usage.
This calculator estimates daily, monthly, and yearly usage. Monthly values are approximated with 30 days, and yearly values with 365 days. That’s usually enough to compare devices (for example: “Should I keep a dehumidifier running 24/7?” or “How much does an electric heater cost per day?”). If you want an even more accurate result, you can adjust the “hours/day” value to match your real usage pattern.
Everything runs locally in your browser. The numbers you enter are used only to compute the result shown on screen; there’s no server calculation and no data storage required for the tool to work.
What is this electricity consumption calculator used for?
This electricity consumption calculator helps estimate how much electrical energy a device uses over time and how much it costs. It converts a power value expressed in watts (W) into kilowatt-hours (kWh), the unit used on electricity bills, and then multiplies it by a price per kWh to estimate the cost in euros.
Who is this tool useful for?
- Home users estimating appliance electricity costs
- Tenants and homeowners comparing energy usage
- Students learning the difference between power and energy
- Consumers comparing efficient vs inefficient devices
- Anyone trying to reduce electricity bills
Concrete examples
- 1000 W heater used 2 h/day → 2 kWh/day
- 2 kWh/day at €0.25/kWh → €0.50 per day
- TV (150 W) used 4 h/day → ~18 kWh/month
- PC (400 W) used 6 h/day → ~876 kWh/year
Common mistakes
A frequent mistake is confusing watts with kilowatt-hours. Watts indicate instantaneous power, not energy consumption. Another common error is forgetting that usage time has a direct impact: a low-power device running all day may consume more energy than a high-power device used briefly.
Limits and considerations
This calculator assumes constant power and average daily usage. Real devices may consume more or less depending on cycles, temperature, efficiency losses, standby modes, or variable load. Electricity tariffs may also vary by time of day or contract.
Educational summary
Electricity cost depends on three things: power (W), time (hours), and price per kWh. This tool applies the standard energy formula to help translate technical specifications into understandable and actionable cost estimates.