Watt (W) is the internationally used unit of measurement for power, i.e. the energy conversion per period of time. Among other things, it can be used to measure the electrical power that is converted into light in an incandescent lamp. In this context, watts are used exclusively to indicate the active power.
Watt is a unit derived from the basic units kilogram, meter and second:
1 W = 1 (kg m2)/s3
Nowadays, it is more common to refer to the values lumen and lux, since the power in watts does not provide sufficient information about the actual lighting behavior of LEDs.