Contents
How the energy converter works
Enter energy in joules or kilowatt-hours. The second field updates immediately, and the middle control reverses the conversion without changing the amount of energy.
From watts and seconds to kilowatt-hours
One joule is one watt-second. A kilowatt-hour is the energy delivered by 1000 watts for 3600 seconds, so it contains exactly 3.6 million joules.
Divide joules by 3,600,000 to get kWh. Multiply kWh by 3,600,000 for the reverse conversion.
Useful scale checks
- 3,600 J = 0.001 kWh. This is also one watt-hour.
- 180,000 J = 0.05 kWh.
- 900,000 J = 0.25 kWh.
- 2 kWh = 7,200,000 J. Reverse conversion produces a larger number because the joule is much smaller.
Energy is not power or an electricity bill
J and kWh both measure energy. Watts and kilowatts measure power, the rate at which energy is transferred. To calculate energy from power, duration is also required.
The converter changes units only. It does not apply an electricity tariff, estimate device efficiency or improve the precision of rounded source data.
Questions about joules and kWh
These answers cover the exact factor and the distinction between energy and power.
How many joules are in one kilowatt-hour?
Exactly 3,600,000 joules.
How do I convert joules to kWh?
Divide the number of joules by 3,600,000.
How do I convert kWh to joules?
Multiply the number of kilowatt-hours by 3,600,000.
Is a kilowatt the same as a kilowatt-hour?
No. A kilowatt measures power; a kilowatt-hour measures energy.
Can this result calculate an electricity cost?
Not by itself. Cost also requires the tariff charged per kilowatt-hour.
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