How do I convert watts to kilowatt-hours?

Multiply the power in watts by the number of hours it runs, then divide by 1000. For example, a 1000 W heater running for 1 hour uses (1000 × 1) ÷ 1000 = 1 kWh.

Is this calculator accurate?

Yes. It uses the exact relation kWh = (watts × hours) ÷ 1000. The only approximation is your own input — real appliances vary their draw, so use the average or rated wattage for an estimate.

Is my data sent anywhere?

No. The calculator is privacy-first — every calculation happens locally in your browser and nothing you type is transmitted or stored.

Watts to Kilowatt-Hours (kWh) Calculator

Watts to Kilowatt-Hours Calculator

Convert an appliance’s power in watts plus its running time in hours into the energy it uses in kilowatt-hours (kWh) — the unit on your electricity bill. The relation is kWh = (watts × hours) ÷ 1000, so a 1000 W appliance running for one hour uses exactly 1 kWh.

Enter the wattage and hours — the result updates in real time, and the reference table shows common wattages at your chosen run time. All calculations run entirely in your browser with no data sent to any server.