kWh to Watt-Hours Converter
Convert between kilowatt-hours, watt-hours, megawatt-hours, joules and megajoules — energy units for bills, batteries and appliances.
How it works
1 kWh = 1000 Wh · 1 Wh = 3600 J · 1 kWh = 3.6 MJ
A watt-hour is the energy of one watt sustained for one hour, and a kilowatt-hour is a thousand of them — the unit your electricity bill uses. Converting to the SI unit, one watt-hour equals 3600 joules because there are 3600 seconds in an hour. These conversions let you compare an appliance’s Wh rating, a battery’s capacity and a physics figure in joules on the same scale.
Worked example
5 kWh equals 5 × 1000 = 5000 Wh. In joules that is 5000 × 3600 = 18,000,000 J, or 18 MJ — the energy a 1000 W microwave would use running continuously for 5 hours.
Frequently asked questions
How do watt-hours relate to watts?
Watts measure power (rate), watt-hours measure energy (amount). A 100 W device running for 10 hours uses 100 × 10 = 1000 Wh = 1 kWh. Multiply power by hours to get energy.
Why is 1 kWh equal to 3.6 megajoules?
1 kWh = 1000 W × 3600 s = 3,600,000 joules, since a watt is a joule per second and an hour is 3600 seconds. Dividing by a million gives 3.6 MJ.
How much does 1 kWh cost?
That depends on your utility rate, typically $0.10–$0.35 per kWh in the US. Multiply your kWh by the rate to get the cost — a dedicated electricity cost calculator handles that.
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