Lumens Vs. Watts

The lumen and the watt are both units of measurement. The lumen is a measure of light while the watt is a measure of power.

What is a Lumen?

Lumens are a measure of the perceived power of light -- i.e. of light you can see. Waves of light that are beyond the spectrum visible to the human eye are not included in the lumen.

What is a Watt?

A watt is defined as the amount of power needed to move a one kilogram (2.2 pound) object at a speed of one meter per second against a force of one newton. In simple terms, it is a measure of the amount of energy something either uses or produces. One watt is equal to 1/746 horsepower.

What is the Difference?

Because watts and lumens are measures of different things, there is not necessarily any correlation between them. For example, a conventional light bulb and a compact fluorescent light bulb may put out the same number of lumens, but the conventional bulb will consume three to five times the number of watts needed by the compact fluorescent.

An Increasingly Common Term

Lumens have come into everyday use largely as a result of the government mandate to phase out incandescent light bulbs in favor of compact fluorescents. Because the two types of bulb consume different amounts of power to produce a given amount of light, lumens offer an easier way for consumers to compare the new lightbulbs with the older ones they are replacing.

Origins of the Terms

"Lumen" comes from the Latin word for "light." The "watt," however, is named in honor of James Watt (1736-1819), a Scottish inventor, in recognition of his contributions to the development of the steam engine.