L80B10: what LED lifetime really means
An LED does not blow: it fades. Its lifetime is therefore not a number of hours but an agreement on how much light will be lost and how many units will have failed.
- Reference standard
- IES LM-80 · TM-21 · IEC 62717
- Scale
- L70 a L90 · B10 a B50
- Where it applies
- Garantía, mantenimiento y factor MF
- How it is measured
- Ensayo 6.000 h + extrapolación TM-21
The notation has two parts. L is the remaining flux: L80 means the luminaire retains 80 % of its initial output. B is the failure rate: B10 means at most 10 % of units will have fallen below that L80. So L80B10 > 60,000 h reads: at 60,000 hours, 90 % of luminaires will still deliver at least 80 % of their light.
Comparing without reading the notation is the classic mistake. A manufacturer publishing L70B50 at 50,000 h is saying something far weaker: that half its units will have dropped below 70 %. On paper the figures look similar; in the installation, one is twice as demanding as the other.
These values are not measured at 60,000 hours — that would be seven years of testing. Testing follows LM-80 for about 6,000 hours and is extrapolated using TM-21. That is why the standard limits how far you may extrapolate: publishing 100,000 h from 6,000 h of testing is not serious.
The practical consequence lies in the maintenance factor (MF) of the lighting calculation. If a project uses MF 0.8, it assumes 20 % less light at end of life — which is why more lumens are installed than strictly needed on day one. A product with better lumen maintenance allows a higher MF and therefore fewer luminaires.
- Always compare the full notation: L80B10 and L70B50 are not comparable.
- Ask at which ambient temperature (ta) lifetime is declared: at 40 °C it falls sharply versus 25 °C.
- Driver life is usually the weak link: ask about it too, not only the LED.
- A good L80B10 lets you raise the MF in the calculation and save luminaires from day one.
