What is the formula used?

The formula is E(J) = P(kW) × t(s) × 1000. This comes from E = P × t where power is in watts (1 kW = 1000 W) and time is in seconds, giving energy in joules (1 J = 1 W · s).

Why multiply by 1000?

Kilowatts must be converted to watts before multiplying by seconds. Since 1 kW = 1000 W, multiplying the kilowatt value by 1000 gives watts, and watts × seconds = joules.

A joule (J) is the SI unit of energy. One joule equals one watt of power sustained for one second. It is also equivalent to one newton-meter of mechanical work.

How does the result relate to kilowatt-hours?

1 kilowatt-hour (kWh) equals 3,600,000 joules. To convert your joule result to kWh, divide by 3,600,000. The result panel shows this conversion automatically.

Can I use minutes or hours instead of seconds?

This tool uses seconds as the time unit, which directly yields joules. To use minutes, multiply your minute value by 60 before entering it. To use hours, multiply by 3600.

Is this valid for AC power?

Yes, for AC circuits enter the real power in kilowatts (apparent power in kVA multiplied by power factor). The formula then gives the real energy consumed in joules.

Kilowatts to Joules Calculator

Enter power in kilowatts and time in seconds to calculate energy in joules using E = P(kW) × t(s) × 1000.

Input Parameters

Power (kW)

Time (s)

Result

Enter values and press Calculate

Formula Reference

Core Formula

E (J) = P (kW) × t (s) × 1000

Unit Conversion

1 kW = 1000 W = 1000 J/s

To Kilowatt-Hours

1 kWh = 3,600,000 J

Result copied!

Summary

This calculator converts power in kilowatts (kW) and a duration in seconds to energy in joules (J) using the formula E = P × t × 1000. Since 1 kilowatt equals 1000 watts and 1 watt equals 1 joule per second, multiplying kilowatts by seconds and by 1000 yields the total energy in joules. The tool is useful in electrical engineering, HVAC, and physics whenever you need to express rated power output as absolute energy over a time window.

How it works

Enter the power value in kilowatts (kW).
Enter the duration in seconds (s).
The calculator applies E(J) = P(kW) × t(s) × 1000.
The primary result is displayed in joules (J).
Additional conversions to kilojoules (kJ), watt-hours (Wh), and kilowatt-hours (kWh) are shown automatically.
Use the Reset button to clear inputs and start a new calculation.

Use cases

Calculate the energy delivered by an electric motor rated in kilowatts over a known run time.
Estimate heat output of a kilowatt-rated heating element in joules.
Convert generator output from kilowatts to joules for energy-storage sizing.
Verify battery capacity requirements for powering a kilowatt load for a set duration.
Compute kinetic energy equivalents in mechanical engineering problems.
Determine energy consumption of industrial equipment during a production cycle.
Translate rated appliance power to absolute energy for billing or auditing.
Support physics coursework requiring SI energy units from kilowatt inputs.

Frequently Asked Questions

Last updated: 2026-05-23 · Reviewed by Nham Vu