Making Sense of Modern Light Bulb Labeling

By Didier Saumon, Jemez Mountains Night Sky Coalition

Buying a light bulb used to be simple. Up until about 15 years ago, nearly all light bulbs on the consumer market were of the incandescent type (with a coiled filament inside), labeled in watts. When we needed a bright light we chose a 100 watt bulb and for applications requiring less light, we chose 40 or 60 watt bulbs.

It’s no longer quite so simple. Light Emitting Diode (LED) technology is rapidly taking over nearly all applications, and there is a much greater variety to choose from. Bulbs and fixtures are now labeled with watts, lumens, and “K,” complemented with terms such as “soft white,” and “daylight.” What does it all mean? This article in our series on light pollution aims to demystify these technical terms to help navigate the purchase of light bulbs and fixtures.

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