About

Power and Energy are often confused, but they are distinct physical concepts. Power, measured in Watts, is the rate at which energy is used. Energy, measured in Joules, is the total quantity consumed or work done. This tool computes the total energy by integrating power over a specific time duration. It solves the common problem of converting time units (minutes, hours) into seconds, which is the required SI base unit for this calculation.

This calculator is widely used by physics students solving work-energy problems and by engineers estimating the battery capacity required for a specific load. For example, knowing that a device draws 50 W for 2 hours allows you to determine the total energy budget in Joules or Kilojoules.

Formulas

Since 1 Watt is defined as 1 Joule/second, the formula for Energy is:

E_(J) = P_(W) × t_(s)

If the time is provided in other units, it must first be converted to seconds:

For Minutes: t_(s) = t_(min) × 60For Hours: t_(s) = t_(hr) × 3600

For large values, the result is often expressed in Kilojoules (kJ):

E_(kJ) = E_(J)1000

Reference Data

Appliance / Load	Power (W)	Duration	Energy (Joules)
LED Light Bulb	10 W	1 min	600 J
Laptop Charger	60 W	1 min	3,600 J
Human Sprinting	1000 W	10 s	10,000 J
Microwave	1000 W	1 min	60,000 J
Electric Kettle	2000 W	3 min	360,000 J
Space Heater	1500 W	1 hr	5,400,000 J
Car Engine (Idle)	10,000 W	1 hr	36,000,000 J

Frequently Asked Questions

A Joule is the derived unit of energy in the International System of Units. It is equal to the energy transferred to an object when a force of one newton acts on that object in the direction of the force's motion through a distance of one meter (1 Newton-meter).

To get kWh, you don't need to convert to Joules first. Simply multiply Power (kW) by Time (hours). However, since 1 kWh = 3,600,000 Joules, you can divide your Joule result by 3.6 million to get kWh.

Yes, you can rearrange the formula: Power = Energy / Time. If you used 500 Joules in 5 seconds, the power rate was 100 Watts.

The relationship E = P × t applies to both AC and DC circuits, as well as mechanical systems, assuming the Power figure (P) represents the average power over the duration.