What L80B10 means, and why the driver matters most.
Learning Track · Module 2: Luminaires · Step 9 of 101
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LEDs usually get dimmer slowly. Lifetime is given as Lx By (IEC 62717, IEC 62722-2-1). Lx means x% of first light remains. By means y% of luminaires are below that level. USA: In the USA, datasheets often give only L70 from a TM-21 projection, which is the median (B50) value.
100,000 h ÷ 4,200 h per year ≈ 24 years
Electronics fail first
In most cases, the driver and surge protector fail before the LEDs. Heat, surges, and a poor supply shorten their life. The driver datasheet gives its life at a stated case temperature (tc point). Life drops quickly above that temperature.
Plan for light loss
Designers use a maintenance factor (light loss factor in the USA) for dirt and LED ageing. Constant light output (CLO) drivers start at lower power and increase it slowly, so the light stays the same and you do not pay for extra light in the first years.
Middle East, South Asia: Dust on the cover can reduce light output much faster than LED ageing. Plan cleaning by the dust level of each area.
Sources
- IEC 62717 LED modules for general lighting: performance
- IEC 62722-2-1 LED luminaire performance
- IES LM-80 Measuring luminous flux and color maintenance of LED packages, arrays and modules
- IES TM-21 Projecting long-term luminous flux maintenance of LED light sources
Changes: 30 October 2026: First publication: guides for Europe, the Middle East, South Asia, and the USA; failure library; tender clause library; comparisons; tools; downloads. See the changelog. Found a mistake? Report it.