For years, homeowners bought light bulbs based on their watt rating; with the understanding that the more watts that the light bulb was rated, the brighter it would be. The truth is the relationship between watts and brightness of light output is rather indirect. A watt is a unit of power, or energy consumed by the light source. A watt rating, as indicated on the traditional incandescent light bulb and on the lighting facts label, represents the amount of watts consumed by the light bulb in one hour of use. If consumers want to buy a light bulb that will emit a certain level of brightness, then they should buy a light bulb based on its rating of lumens.
A light bulb that produces more lumens using fewer watts is more energy efficient. Mathematically, the proportion of lumens to watts consumed is actually an industry standard measurement referred to as a light bulb’s efficacy.
Many building codes and regulations of energy efficiency have adopted this metric to mandate that homeowners and business owners maintain certain levels of efficacy by their normally operating lights.
Once incandescent lights are no longer on the shelves of America’s favorite retail stores, consumers will be forced to recognize the lighting watt paradox. This unfortunately popular misunderstanding will then be phased out with the
incandescent lights themselves, and light bulbs will be appropriately compared on the basis of lumens. Since incandescent lights consistently produce proportional brightness to watts burned, this table can help transition the thought process from watts to lumens.