kWh to Joules

A kilowatt-hour measures energy, not power: it is the energy used when a device drawing 1 kilowatt runs for 1 hour. The conversion works because 1 watt equals 1 joule per second, so 1 kilowatt-hour = 1000 joules/second × 3600 seconds = 3.6 × 10^6 joules. Multiplying by 3.6 million turns the electricity-billing unit into the SI energy unit.

Use this when you need to convert electricity usage from a bill or appliance rating into joules for physics calculations. It is common in energy, power, and efficiency problems.

• Using 3.6×10^3 instead of 3.6×10^6
• Confusing kilowatt-hours with kilowatts
• Forgetting that the result is an energy value in joules