How is the average rated life of LED light bulbs calculated?
While an LED can generate light for up to 100,000 hours, its lumen output gradually decreases over time. The industry standard is to provide a life rating that is the point at which the lumen maintenance is 70%. In other words, the average rated life for an LED tells you how many hours the LED will last and maintain at least 70% of its initial lumen output. This is different from how the average rated life is determined for other light sources (incandescent, halogen, fluorescent, etc.). Other light sources measure the average rated life as the point at which 50% of the bulbs tested have failed and 50% of the bulbs tested are still burning. LED light bulbs measure the point at which they provide 70% of initial lumens because LEDs fade over time, and this rating gives end users an idea of how long the LEDs will provide useable light that meets the needs of the application.
