Wattage is a measure of how much energy a light bulb uses. In fact, it has nothing to do with the actual brightnLEss of a light bulb. Over time, consumers tend to gain a general idea of how bright a 60-watt light bulb is compared to a 100-watt light bulb. Because of this, people tend to associate the brightness of a light bulb based with its wattage rating. When looking at incandescent lights, this method for comparing brightness is useful. However, where other types of lights like LEDs are concerned, this method is useless.