How it works
How to calculate it
The calculator applies the values you enter to this formula:
Cost = (watts ÷ 1,000) × hours per day × days × electricity rate.
How to use this calculator
- Find device wattage.
- Estimate active hours per day.
- Enter the number of days and energy rate from your bill.
Worked example
A 1,000 W device used four hours daily for 30 days consumes 120 kWh and costs $20.40 at $0.17/kWh.
Important assumptions
- The device runs continuously at the entered wattage.
- Taxes, fees, and tiered utility pricing are excluded.
- Use the wattage label or a plug-in power meter for better accuracy.
Common mistakes to avoid
- Treating watts as kilowatt-hours.
- Using elapsed time for a cycling device.
- Applying the full utility bill average without understanding fixed charges.
Method reviewed June 10, 2026. Prices and rates are user-provided defaults and should be replaced with local values.