LightingEurope Tackles LED Luminaires’ Dirty Little Secret

The dirtiest little secret in LED lighting is that luminaire lifetime values are nearly meaningless for the vast majority of luminaire manufacturers. Why is this? Two reasons:

• First, all manufacturers typically report TM-21 LED chip projected lumen maintenance values as the luminaire lifetime. This does not include the driver nor other components. Drivers have historically been the weak link component that failed first in LED luminaires. Therefore, the TM-21 value is practically irrelevant, when the driver fails before the chip lumen maintenance projection presented, be it L₇₀, L₈₀, etc. I have heard from smart engineers that driver lifetime has been improving significantly, in recent years.
• Second, the vast majority of LED luminaire manufacturers violate TM-21 lumen maintenance projection methodology by exceeding the requirement that LED chip lumen maintenance projections may not exceed 6X the hours tested in the LM-80 test. Often LM-80 testing is for 6,000 hours, meaning the 6X limit for claimed lifetime is 36,000 hours. If an LM-80 test was 8,000 hours the maximum TM-21 claim should not exceed 48,000 hours. Most manufacturers claim 50,000 hours to 100,000, violating the 6X extrapolation limit. A few highly reputable manufacturers avoid this abuse by giving L80 or L90 lumen maintenance / lifetime values that remain below the 6X extrapolation limit. For example, L90 of 36,000 hours does not violate a 6X extrapolation of 6,000 hours of LM-80 test data. The luminaire manufacturers that obey the 6X extrapolation limit can probably be counted on two hands.

These problems have existed and been discussed in lighting standards circles for at least the last 10 years and probably longer. However, no remedy has been provided in North America.

LightingEurope, a lighting trade association in Europe, released a new set of recommendations for improvingLED luminaire lifetime values. This guiding paper was released in January, 2025. LightingEurope is recommending that luminaire manufacturers publish:

• “Initial performance data set,” including ambient temperature of luminaire when tested, input power, luminous flux, luminous efficacy, CCT, and CRI.
• “The lumen maintenance factor ‘x’ (in %) at Median Useful Life (Lx) values of 35k, 50k, 75k and/or 100k hours, related to the applications where the product may be used;”
• “The expected ‘control gear failure rate (in %)’ at the same number of hours specified in the Median Useful Life(s).”

An example of the luminaire reporting recommendations is in the chart below. Based on my read, these recommendations address the driver lifetime through the “Abrupt failure value (%) at Median useful life.” I did not see any reference to manufacturer abuse of the 6X extrapolation limit in TM-21, but this is likely because the European testing standards are IEC standards and not IES TM-21. European manufacturers may or may not abuse testing hour extrapolation limits, as is routinely done by North American manufacturers. If any readers are familiar with IEC standards for lumen maintenance projections and whether the same abuses of extrapolation limits occur in Europe, please email me at david@lightingsold.com . I will update this article with any well-cited corrections that I receive.

It is long past time for the North American luminaire market to create meaningful luminaire lifetime metrics that address driver failure, and the TM-21 6X extrapolation limit abuses. I welcome any technical corrections to this article.

The complete LightingEurope Guiding Paper is free to download here.

All images: LightingEurope Guiding Paper with recommendations for expressing LED luminaire lifetime.

David Shiller

David Shiller is the Publisher of LightNOW, and President of Lighting Solution Development, a North American consulting firm providing business development services to advanced lighting manufacturers. The ALA awarded David the Pillar of the Industry Award. David has co-chaired ALA’s Engineering Committee since 2010. David established MaxLite’s OEM component sales into a multi-million dollar division. He invented GU24 lamps while leading ENERGY STAR lighting programs for the US EPA. David has been published in leading lighting publications, including LD+A, enLIGHTenment Magazine, LEDs Magazine, and more.

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