The watt (symbol: W) is the SI derived unit for power. It is equivalent to one joule per second (1 J/s), or in electrical units, one volt ampere (1 VˇA).
It is the rate in joules per second at which energy is being converted, used, or dissipated.
The unit watt is named after James Watt for his contributions to the development of the steam engine, and was adopted by the Second Congress of the British Association for the Advancement of Science in 1889 and by the 11th Conférence Générale des Poids et Mesures in 1960.
1 MWd or MWˇd (megawatt day) = 86.4 GJ, a unit used in the context of power plants.
For the use of watts as a measurement in broadcasting, see effective radiated power and nominal power for a full discussion.
SI electricity units