definition

Power

Power is the rate at which energy is transferred or work is done. Its SI unit is the watt.

By AskToBot Editorial Team · Updated October 5, 2026

Power is the rate at which energy is transferred or work is done. Its SI unit is the watt.

Simple example

One watt means one joule per second. A 10 W device operating for 10 seconds transfers 100 joules.

Read units together with the number. A value without its unit can be ambiguous; a ratio such as a percentage also needs its reference whole.

Use the Power Calculator to connect the concept to a worked calculation.

Calculate electrical power for DC or ideal resistive loads.

Estimate distance from average speed and travel time.

Energy is a physical quantity associated with the capacity to do work or transfer heat. The SI unit is the joule.

Estimate electrical energy in kilowatt-hours from watts and hours.

Divide total distance by total elapsed time.

For DC circuits, multiply voltage by current: P = V × I.

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