Watt

The power (symbol P) of a light fixture is measured in watts (abbreviated as W). This provides information about a light source’s energy or electricity consumption. This unit was named after the Scottish scientist and engineer James Watt, who became known for improving the efficiency of steam engines. A good rule of thumb is: The higher the wattage, the more energy is consumed. In the past, wattage values were often used to compare the brightness of lamps, but thanks to modern, energy-saving technology, this is hardly informative anymore. Many years ago, when only incandescent bulbs—which consumed a relatively large amount of energy—were available, it was sufficient to look at the wattage. Nowadays, however, energy-efficient LED bulbs have long been available, some of which require only 8 to 9 watts, while a conventional incandescent bulb needs a full 60 watts to produce the same brightness. This already makes it clear that comparing brightness in watts no longer makes sense, which is why lumen values are now used for comparison instead. As a rule of thumb, you can remember that the conversion factor is roughly 10—in other words: lumens = watts × 10. Power in watts is closely related to voltage in volts and current in amperes, since the formula is as follows: watts = volts × amperes. These three quantities are thus interconnected in a certain way, and they can be used, among other things, to calculate when a fuse will blow—which, of course, must be prevented.