Genura vs Cree LEDs

bugbiteJune 1, 2009

A China manufacturing site was discussing the problems that they must overcome with LED lighting. A side note mentioned that LEDs lumens decline overtime. I was disturbed when I saw GE's published decline from 1100 lumens to 770 lumens with the Genura. Thought that helped justify the Cree because I thought LEDs don't decline. Then I read the Chinese thing and another US article:

"LEDs may last longer than fluorescents, but they are hugely more

expensive to buy. The datasheets from the LED manufacturer's

typically list a 50,000 hour from beginning to 70% of original output,

lifetime. But none of them provide a lifetime curve. So we don't

know if that means that LEDs have a linear decline from 100% to 70%

output over 50,000 hours, or whether the output declines steeply early

on and then declines shallowly (bad), or whether it keeps its output

near 100% for most of that time and declines steeply towards the end

of 50,000 hours. Which is it? No publicly available information.

For comparison, General Electric lists a 30,000 lifetime for its T5

fluorescent bulbs until output declines to 80% of original. And they

provide lifetime output curves to show you how the decline in output

will occur.

White LEDs are actually ultraviolet LEDs with a phosphor coating which

converts the ultraviolet energy into white visible light. So, most

likely, they will decline in output in a fashion very similar to

fluorescent light bulbs, because they are both using the same method

of converting ultraviolet radiation into visible light.

.....

Jeff Walther "

That's not me; that is the guy that posted the comments on his site.

Update: I called Cree. They were very nice. Transfered me 4 times up the chain till I got a very knowledgable, nice person. He said that the Cree LR6C go up in lumens for the first 1000 hours and then start a slow steady decline in lumens until it reaches about 70% of the 650 initial lumens in (get this) 55,000 - 60,000 hours. That's 7 years if you leave it on 24 hours a day, he said; 30 years in a typical home. The world of lighting will be different in 20 years, so no worries if I want to change the bulb in 20 years :-)

The lumens quote CREE gives is impressive because they measure the output from the actual fixture, not the bulb which loses lumens as it travels out of and bounces around the fixture. Still considering the Genura, however. (and a TCP Springlamp).

Bob

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