L70 Rated Life (L70)

L70 is the operating time after which an LED product’s light output is projected to fall to 70% of initial — the industry’s standard definition of useful life, since LEDs dim rather than fail abruptly. A rating of “L70 ≥ 50,000 h” means the fixture should still deliver at least 70% of day-one lumens after 50,000 hours (about 11 years at 12 h/day). Projections derive from LM-80 chip test data extrapolated by the TM-21 method at the fixture’s real operating temperature, which is why thermal design — not chip choice alone — determines honest lifetime. Variants like L80 or L90 state stricter thresholds for lumen maintenance.