Watts to Wh Calculator
Convert watts to Wh by multiplying power by running time in hours. Formula, worked example and a table of typical values. Watts are power, Wh is energy.
Try your own numbers
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
| Input | Value |
|---|---|
| Power | 250 W |
| Time | 2 h |
- E = P × t = 250 W × 7,200 s = 1,800,000 J
- In other units: 0.5 kWh = 1.8 MJ; 0.25 kW; 2 h
Typical values
| Time (h) | Energy (Wh) |
|---|---|
| 0.5 | 125 |
| 1 | 250 |
| 2 | 500 |
| 5 | 1,250 |
| 8 | 2,000 |
| 24 | 6,000 |
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 Wh?
E = P × t (1 W × 1 s = 1 J, 1 kW × 1 h = 1 kWh = 3.6 MJ). Worked example: Power 250 W, time 2 h gives 500 Wh.
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 Wh?
kW is power, the rate of using energy. Wh is energy, power multiplied by time. A 1 kW load running for 1 hour uses 1,000 Wh, so kW cannot be converted to Wh without a time.
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: Wh to Watts
Also see: Lumens to Watts Watts to Lumens Lux to Watts Watts to Lux
Formula guides: Energy and Cost Formulas: kWh and PaybackEnergy ConverterElectrical Unit Converter
All 78 conversionsWatts, Joules, kWh and Time (any two) in Elecmetric