Battery & energy
kWh Calculator
Kilowatt-hours equal watts multiplied by hours and quantity, divided by 1,000. This converts steady power use into accumulated energy.
Convert watts and operating time into watt-hours and kilowatt-hours for one or more identical loads.
Calculated result
Calculated energy use
Calculating…
Calculated locally in your browser
Planning math only. Verify equipment specifications and installation requirements separately.
What this calculator returns
Energy accumulates over time; a kW rating alone is power, not energy.
Formula and variables
The calculation runs entirely in your browser. Static formulas, definitions, examples, and tables remain readable without JavaScript.
kWh = watts x hours x quantity / 1000.
- W
- Average real power in watts.
- h
- Operating or charging time in hours.
- kWh
- Accumulated electrical energy in kilowatt-hours.
- rate
- User-entered electricity price per kilowatt-hour.
- η
- User-entered efficiency expressed as a decimal or percentage.
Watts is real power, hours is operating time, and quantity is the number of identical loads.
Worked example
| Input | Value |
|---|---|
| Power | 1000 W |
| Operating time | 3 h |
| Quantity | 1 |
A 1,000 W load operating for 3 hours uses 3,000 Wh, or 3 kWh.
Reference table
| Use case | Energy | At $0.15/kWh | At $0.30/kWh |
|---|---|---|---|
| 1 kW for 1 hour | 1 kWh | $0.15 | $0.30 |
| 1.5 kW for 4 hours | 6 kWh | $0.90 | $1.80 |
| 30 kWh EV session | 30 kWh | $4.50 | $9.00 |
| 900 kWh billing period | 900 kWh | $135.00 | $270.00 |
Frequently asked questions
What is the difference between kW and kWh?
kW is power at a moment; kWh is energy accumulated as power is used over time.
How many kWh does a 1 kW load use in one hour?
A steady 1 kW load operating for one hour uses 1 kWh.
What is the difference between kW and kWh?
Kilowatts measure power at a moment; kilowatt-hours measure that power accumulated over time.
Assumptions and limitations
- Assumes constant average power during the entered time.
- No tariff, battery, or demand-charge model.
Method and sources
Review the electrical formulas, calculation methodology, and standards status for the references most relevant to this calculation. The broader technical sources index records source scope and verification. Last reviewed .