Energy in kilowatt-hours equals watts multiplied by operating hours, divided by 1,000. Multiply that result by the number of devices, days and your entered rupees-per-kWh rate to estimate the variable energy charge. Use measured or documented operating power—not a power supply's maximum capacity—and remember that real bills can include slabs, fixed charges, taxes and other items this tool does not calculate.
Estimate device kWh and variable energy cost
Enter measured or representative operating watts and your own current energy rate. The result is not a complete electricity bill.
The calculator uses one visible energy formula
| Result | Formula | Meaning |
|---|---|---|
| Daily energy | watts × quantity × hours ÷ 1,000 | kWh for the entered daily operating period |
| Period energy | daily kWh × days | Variable energy use over the selected period |
| Estimated cost | period kWh × entered ₹/kWh | Energy-only estimate before other bill components |
| One electricity unit | 1 kilowatt-hour | CEA metering terminology used in India |
The result is only as useful as the power input
A desktop power supply marked 650 W can deliver up to a rated output under specified conditions; it does not mean the computer continuously draws 650 W. Computers also move among active, idle, sleep and off states. ENERGY STAR evaluates computer efficiency across multiple modes and power-management behavior.
Use a safe, suitable energy meter or a documented measured value for the actual workload when available. If you only have a maximum rating, label the result as an upper-bound scenario rather than normal consumption.
- Separate computer, display, printer, router and other always-on loads
- Model active and idle periods separately when they differ materially
- Use the current bill or utility schedule for the tariff input
- Do not treat this estimate as a utility quotation or electrical safety assessment
Billing and safety boundaries
Electricity tariffs can use consumption slabs, fixed or demand charges, duties, taxes, rebates and time-based rules. This tool multiplies one user-entered rate by estimated kWh and cannot reproduce a complete bill unless that single rate already represents the intended scenario.
Do not open a power supply, mains socket, UPS or distribution board to obtain a reading. Use rated measurement equipment in the intended way or obtain qualified electrical support.
Sources and further reading
Technical statements were reviewed against these references. External pages may change after our review date.
- Central Electricity Authority Regulations Compendium — Metering and Active Energy — Central Electricity Authority, Government of India
- Computers — ENERGY STAR
- The International System of Units: SI prefixes — Bureau International des Poids et Mesures