Lumen Maintenance is a measurement used to evaluate the decrease in light output of a bulb that occurs over time. LED light bulb life is defined as when the light bulb produces 70% of the initial lumens (L70).
The L70 rating measurement lets you know how long you can depend on an LED to provide an acceptable level of intensity as the day you installed it. LED must maintain 70% of their initial lumens during their rated life. For example, an LED with a life of 50,000 hours means that at 50,000 hours of use, the LED bulb will be producing 70% of the light output that it was producing when it was brand new. A light source which emits 1,000 lumens when new and 700 lumens after 50,000 hours of use has a lumen maintenance of 70% at 50,000 hours (L70 of 50,000 hours).
Visit the IES website to learn more.