100watt

100 watt, usually written as 100 W, is a common power rating used in physics, engineering, and consumer products. The watt (W) is the SI unit of power, defined as one joule of energy transferred per second. Therefore, 100 W corresponds to a rate of energy transfer of 100 joules each second. The term can describe electrical power, mechanical power, or any situation in which energy flow is quantified over time. In electrical contexts, power can be calculated as P = V × I, so a device drawing 100 V at 1 A consumes 100 W.

The designation appears on many products to indicate energy use or output. In lighting, 100 W historically referred to incandescent bulbs, which produced around 1600 lumens but used substantial electricity. With modern lighting, light-emitting diodes provide similar brightness at far lower wattages, typically around 12–20 W for a lamp that would have been a 100 W incandescent. In audio and electronics, devices may be labeled 100 W to indicate maximum continuous power output (as in amplifiers) or maximum input power (as in power supplies). In such cases, the exact meaning depends on the product and its specifications.

Historically, the watt is named after James Watt, and the 100 W rating remains a practical reference point for comparing energy consumption and performance. Regional energy efficiency standards have reduced the use of 100 W incandescent sources, promoting higher-efficiency alternatives. See also: watt, power, luminous efficacy, energy efficiency.