Watts to kWh Calculator
Convert watts to kilowatt-hours and estimate electricity cost over time with this free power usage calculator in your browser.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the power and hours of use.
- Press Calculate.
How it works
Energy (kWh) = power in watts ÷ 1,000 × hours of use.
Worked example
2,000 W for 3 hours. = 6 kWh.
Common mistakes
- Forgetting to divide watts by 1000 — kWh uses kilowatts, not watts.
- Using minutes as hours — convert run time to hours first.
Frequently asked questions
How do I convert watts to kWh?
kWh = watts ÷ 1000 × hours. A 1,500 W appliance run for 4 hours uses 1.5 × 4 = 6 kWh.
Is a kWh the same as a ‘unit’ on my bill?
Yes — retailers bill in kilowatt-hours, so one unit on your electricity bill equals one kWh.
How do I turn kWh into a dollar cost?
Multiply the kWh by your electricity price per kWh. The energy cost calculator does this and projects daily/monthly costs.
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- Energy Cost Calculator
- Power Converter
- LED Savings Calculator
- Generator Fuel Consumption Calculator
- Electricity Cost Calculator
- Amps to Watts Calculator
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Cite this tool
Zerdly. (2026). Watts to kWh Calculator. Retrieved from https://www.zerdly.com/tools/watts-to-kwh-calculator/
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.