Watts to kWh Calculator

Convert Watts to kWh with the formula, a worked example and a table of typical values. Working shown step by step.

Estimate only. Not engineering or safety advice. Check the result against the applicable standard and the equipment data, and have a competent engineer review it before it is relied on. Terms of use.

Open in the calculator with these values

Formula

Worked example

1. E = P × t = 500 W × 21,600 s = 10,800,000 J
2. In other units: 3 kWh = 10.8 MJ; 0.5 kW; 6 h

Typical values

Other inputs are the same as in the worked example above.

Assumptions

• Constant power over the whole time
• Real (active) power, not apparent power

Change any unit to read the answer in kWh, Wh, kJ or MJ. For a varying load the result is the average power or the total energy, not the instantaneous value. For a cost, use Energy and Cost.

Frequently asked questions

How do I convert Watts to kWh?

E = P × t (1 W × 1 s = 1 J, 1 kW × 1 h = 1 kWh = 3.6 MJ). Worked example: Power 500 W, time 6 h gives 3 kWh.

What do I need to enter?

Enter power, energy and time. Leave blank the value you want to find, and the form solves for it. Change the unit of a value with its selector and the result stays the same.

What is the difference between kW and kWh?

kW (or W) is power, the rate at which energy is used. kWh (or Wh) is energy, power multiplied by time. A 1 kW load running for 1 hour uses 1 kWh.

How accurate are the results?

Every figure comes from the same tested engine as the Elecmetric calculators and is meant for estimating. Check design values against the standard and the equipment data you work to.

Related

Next steps in a design: kWh to kWEnergy ConsumptionEnergy Unit Converter
Opposite direction: kWh to Watts
Also see: Ah to kWh kWh to Ah VA to Watts Watts to VA
Formula guides: Energy and Cost Formulas: kWh and PaybackEnergy ConverterElectrical Unit Converter
All 78 conversionsWatts, Joules, kWh and Time (any two) in Elecmetric