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How Long Do LEDs Last?

(March 2010) posted on Wed Feb 10, 2010

Nisa explains the “second-half syndrome.”


By Dr. Nisa Khan

As president of LED Lighting Technologies, Dr. M. Nisa Khan consults in the solid-state lighting industry and educates consumers about LED lighting. She has a bachelor’s degree in physics and mathematics, and master’s and Ph.D. degrees in electrical engineering. Email her at nisa.khan@iem-asset.com.


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Popularity begets popularity. Particularly today, because of the countless electronic communication systems that quickly dispatch popular news and information across the globe. Ask Tiger Woods. Today, the news travels – and aggrandizes – quickly.
In the scientific arena, popularity describes a matter, concept or idea that races across a given field, and later, perhaps, the nation or world. However, with science, a rise in popularity does not indicate a rise in validity.
For example, when a colleague recently remarked that LEDs last forever, I lightheartedly, but truthfully said only half will last a portion of forever. My reason? Lighting-industry professionals comprehend that a specific lamp series may be publicized to have a three-year life, but also recognize that only half the lamps are expected to last that long. The remainder may last only a fraction of three years. Some call this the “second-half” syndrome.
The “LED lamps operate interminably or almost forever” belief unfurls because casual observers read LED manufacturers’ claims of 100,000-hour lifespan. Unfortunately, such claims and beliefs have become popular, but nothing could be further from the truth. A classic fallibility example is the partially darkened, LED-arrayed, traffic lights we sometimes see.
Too often, the “second-half” failure syndrome frustrates signage and luminaire makers, especially if the lamps burn out within months or days of installation.
If prosaic traffic-signal LEDs experience lifespan problems, what can we expect from modern, but not-so-well-tested LEDs, especially the much-lauded, white ones?


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