What’s the Difference between LM80 and TM-21 for LED Street Lighting

What is LM80? LM-80 refers to a method for measuring the lumen depreciation of solid-state light sources, such as LED packages, modules, and arrays. Before the advent of LM-80, LED component manufacturers each reported lumen maintenance data using their own disparate and varied systems. It was developed by the Illuminating Engineering Society of North America (IESNA), to allow people the ability to evaluate and compare the lumen maintenance of LED components from different companies. It is typically a 6000hr test (can be 10,000hrs) that shows depreciation and chromaticity shift over the period at particular operating temperatures 55 degrees, 85 degrees, and a third manufacturer defined temperature, say 105 degrees.

In 2011, the Illuminating Engineering Society (IES) published the TM-21 guidelines titled “Lumen degradation lifetime estimation method for LED light sources.” TM-21 is the illuminating Engineering society of North America (IESNA) approved method for taking LM80 data and making useful LED lifetime projections from it. The standards apply to lifetime projection of LED package, array or module alone. The result may be used for interpolating the lifetime of an LED light source within a system (luminaire or integrated lamp) using the in-situ LED source case temperature.

What TM-21 does provide is a projection of the lumen maintenance of an LED source (package/array/module) based on data collected according to LM-80. This projection information can then be used to project the expected lumen degradation of the light source as part of a complete system (fixture).