LED Lifespan (L70)
The number of hours until an LED degrades to 70% of its original brightness (L70). Typical LED bulbs are rated 25,000-50,000 hours.
When an LED bulb box says "25,000 hours," it doesn't mean the bulb will suddenly go dark at hour 25,001. It means that's the L70 point — the estimated time until brightness drops to 70% of the original output. At that point, the bulb is still working, just noticeably dimmer than when new.
25,000 hours sounds enormous, but context matters. At 3 hours per day, that's about 22 years. At 8 hours per day (a kitchen or office), it's about 8.5 years. And those ratings assume ideal conditions — good ventilation, compatible dimmer, stable voltage. Put that same bulb in an enclosed fixture with no airflow and the actual lifespan might be half the rated number.
Commercial LED fixtures often quote 50,000-100,000 hours, but they also have larger heat sinks and better drivers. The gap between a $3 bulb and a $10 bulb isn't just brightness or CRI — it's whether you're replacing it in 5 years or 15. Over time, the more expensive bulb usually costs less.
Specifications
| L70 | 70% of original lumens |
| L80 | 80% of original lumens |
| Typical bulb | 25,000 hours |
| Commercial LED | 50,000-100,000 hours |
Related Terms
- Heat Sink
A component (usually aluminum) that absorbs and dissipates heat from LED chips. Critical for lifespan — LEDs don't burn out, they overheat.
- LED Driver
A power supply that regulates current to LEDs, preventing flickering and enabling dimming. Every LED has one — either built into the bulb or as an external unit.
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