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Joules to Kilowatt-Hours Converter
↔ Convert kWh to J instead

Common Conversions

J kWh
1000 0.000278
10000 0.00278
100000 0.0278
500000 0.139
1000000 0.278
3600000 1
5000000 1.389
10000000 2.778
36000000 10
100000000 27.78
3600000000 1000

Why this conversion matters in chemistry

Industrial electrolysis is the place this conversion stops being academic. Aluminum smelting in a Hall–Héroult cell consumes roughly 14 kWh per kilogram of Al — a figure that drops straight out of three moles of electrons per mole of Al, Faraday's constant, and the real-world cell voltage of about 4 V. The arithmetic anchors on 1 kWh = 3.6 × 10⁶ J, which is just 1 kW sustained for an hour written out long. A Faraday's worth of charge pushed through 1 V takes 96,485 J, or about 0.0268 kWh per mole of electrons. From there, every electrochemical-process energy budget — chlor-alkali, copper refining, water splitting — scales by moles, voltage, and cell efficiency.

Formula

kWh = J / 3,600,000

Worked Examples

3600000 J = 1 kWh

The definition — 1 kW sustained for an hour is exactly 3.6 MJ.

96485 J = 0.02680 kWh

The energy to push one mole of electrons through a 1 V potential — a Faraday-equivalent in kWh terms.

285800 J = 0.07939 kWh

The heat released when one mole of hydrogen burns to liquid water, from the standard ΔH°comb of −285.8 kJ/mol.

1000000 J = 0.2778 kWh

One megajoule — about the energy released by 30 mL of gasoline at full combustion.

Frequently Asked Questions

How do I convert joules to kWh?
Divide by 3,600,000. So 7,200,000 J is 2 kWh. The factor comes from 1 kW × 3600 s, which is 3.6 × 10⁶ J exactly.
When does a chemist actually use kWh?
Electrolysis calculations — aluminum smelting runs at around 14 kWh per kilogram of Al, for example — and anywhere battery or process chemistry meets an electricity bill. Energy densities of storage systems are often quoted in Wh kg⁻¹ for the same reason.
How does Faraday's constant relate to kWh?
F = 96,485 C/mol. Energy per mole of electrons at a potential V is FV joules, which at 1 V is 96,485 J or 0.0268 kWh per mole of electrons. Multiply by cell voltage and moles reduced or oxidized to get the total energy for a given electrolysis.
What do chemical fuels look like in kWh?
Hydrogen works out to about 33 kWh/kg on a lower heating value basis; gasoline is around 12 kWh/kg; methanol is around 6 kWh/kg. Those numbers come from standard combustion enthalpies in kJ/mol divided by molar mass and converted through the 3.6 MJ/kWh factor.