360

In terms of electromagnetism, one watt is the rate at which work is done when one ampere (A) of current flows through an electrical potential difference of one volt (V).

Also, in terms of classical mechanics, one watt is the rate at which work is done when an object's velocity is held constant at one meter per second against constant opposing force of one newton.

When a light bulb with a power rating of 100W is turned on for one hour, the energy used is 100 watt-hours (W h), 0.1 kilowatt-hour, or 360 kJ.