Enter kilowatt-hours to find the equivalent energy in joules, or use power in kW and running time to calculate it first.
Table of contents
How to use our kWh to Joules Converter
- Choose the source values you have under "What do you have?"
- Choose "Energy in kWh" if a bill, meter, portal, appliance record, or worksheet already gives an energy amount.
- Enter the value in "Energy (kWh)" and select "Calculate." You can enter a plain number, a properly grouped number such as 1,000, or a value followed by kWh.
- Choose "Power in kW and time in hours" if you have a power rating and an elapsed running time instead.
- Enter "Power (kW)" and "Time running (hours)," then select "Calculate." For example, 1.5 hours means 1 hour and 30 minutes.
- Read "Energy in joules" for the conversion. In the power-and-time path, check "Energy calculated from power and time" to confirm the kWh amount used.
Definitions
Joule (J): The standard international unit of energy.
Kilowatt-hour (kWh): A unit of energy equal to using 1 kilowatt of power for 1 hour. [1]
Kilowatt (kW): A unit of power, which is the rate energy is used or produced. Power needs a time period to determine energy.
Elapsed time: How long equipment actually runs, measured here in hours.
Common mistakes and quick fixes
Mistake: Entering a kW rating as though it were kWh.
Fix: kW is power, not energy. Choose "Power in kW and time in hours" and enter both the power rating and elapsed time.
Mistake: Using a clock time instead of a duration.
Fix: Enter how long the equipment ran. For example, enter 1.5 for one hour and 30 minutes.
Mistake: Typing a comma as a decimal mark, such as 1,5.
Fix: Use a decimal point for fractions, such as 1.5. Use commas only for thousands grouping, such as 1,000.
Mistake: Adding electricity prices or bill fees.
Fix: This calculator converts energy units only. Prices and fixed charges do not change the number of joules.
Limitations & Key Assumptions / Boundary Conditions
- The conversion is exact: 1 kWh equals 3,600,000 J.
- In the power-and-time path, the calculation assumes the entered power stays constant for the full entered running time.
- An appliance label may show rated or maximum power. Actual power use can change with settings, load, and operating cycles.
- This converter does not estimate electricity cost, utility charges, or energy losses.
- Zero and negative entries keep their sign in the conversion. Negative energy may be useful in technical data, but it is not typical household energy use.
Methodology
Conversion method
A kilowatt is 1,000 joules per second, and one hour is 3,600 seconds. Therefore, one kilowatt-hour equals 3,600,000 joules.
joules = energy in kWh * 3,600,000
Power and time method
If you start with power and elapsed time, the calculator first finds energy in kWh, then converts that energy to joules.
energy in kWh = power in kW * time in hours
joules = power in kW * time in hours * 3,600,000
Worked example
A device using 1.5 kW for 0.25 hours uses 0.375 kWh. Multiplying 0.375 by 3,600,000 gives 1,350,000 J.