Intelligent Energy

More LED truths and half-truths

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As Philips unveils its brightest LED bulb ever - equivalent to a 75-watt incandescent - we illuminate how long these things will really last.

Like you, I’ve grown up counting numbers using the “base ten” system, also known as the “decimal” system. You know: one through ten, start again. I’m also familiar with the two-digit binary system of zeroes and ones.

Now, as the world of illumination moves impressively towards energy LEDs, I’m coming to grips with what I’ll call the LED numeral system. LED, of course, stands for “light emitting diode,” but I’ll give it a second meaning: Loosely Estimated Digits.

That’s because some of the numbers that the industry bandies about prompt that familiar gut reaction: “how do they know that?”

Nothing illustrates this better than claims of how long a bulb will last. I’m still saying “wow”, a year after first hearing that an LED bulb lasts 25 years and can even go for 50. (Any normal person would be astonished by that, doubly so for me because I live in the UK, where it’s common for an incandescent bulb to fail instantly. But that’s another story, about Britain's Stone Age consumer ethos, which if Bill Bryson doesn’t wish to tell, I will).

So, do LED bulbs last 50 years? 25? 17? 15? I’ve heard all those from vendors. And, as readers of this blog have reported, LED bulbs can live a shockingly short few months.

Not even the manufacturers know the real truth. I’ve recently come into possession of 4 Philips 12-watt LED bulbs, courtesy of Philips. Looking closely at the packaging, Philips rates them all at a brightness of 806 lumens, all as the equivalent of a 60-watt incandescent bulb, all as “dimmable” and all at a reasonably warm color temperature of 2700 Kelvin (for the those uninitiated to Kelvin counter intuitiveness, the higher the number, the colder the feel of the light; a 5000 Kelvin light might make you feel like you’re in a refrigerator; at 1,000 you’re having a candlelight dinner). All say “made in China.”

The vital statistics were all exactly the same, so Philips must rate them all with an equivalent number of years lifetime, right? BWEEEP! BWEEP! BWEEP! Wrong! The packaging on two of them carried an assurance of 25 years, and on the other two, 15 years.

What’s going on here? Has Philips already decided to tone down the rhetoric by randomly lopping 10 years off the proclaimed lifetime? Is Philips factoring in field reports such as those from the readers of this blog who reported ridiculously short failure rates - not necessarily on Philips brands?

There was one difference between the two sets of bulbs. The two 25-year-bulbs came in stylish see-through packaging from Philips’ continental European operations, which brand the bulb as “MyAmbiance.” The two 15-year-bulbs came from the company’s UK team, in standard, sturdy-looking, functional cardboard boxes, which instead of “MyAmbiance” carried the functional brand “Master” and “LEDbulb MV.”

Was 15 years perhaps a matter of British understatement? Are British regulators stricter than their European counterparts? The British packaging included a small note saying that it based the 15 years on weekly usage of 4 hours per day. The European package offered no such fine print, at least not that I could spot on the label’s microscopic lettering.

I spoke by phone today with the CEO of Philips Lighting North America Zia Eftekhar, who was in Philadelphia to introduce the 17-watt LED bulb rated at 1100 lumens (pictured). It's Philips’ brightest LED bulb to date and the equivalent of a 75-watt incandescent, which is the second most common indoor bulb in the U.S., after 60-watts. Philips hopes to make a big splash with the bulb at Philadelphia’s 3-day LightFair International conference this week.

He suggested that indeed, Philips’ European division might have based its 25-year claim on less frequent usage than the UK’s. But, as CEO of North America, he was not involved in that decision.

For its part, Philips North America is rating its new 17-watt EnduraLED at the same 25,000 hours, but, as the LED numeral system would have it, at a yet again different number of years: not Europe’s 25, not the UK’s 15, but 17 years.

Philips is offering a 5-year warranty. Why not a 17-year warranty? Eftekhar pointed out that manufacturers of all sorts of electronics products do not issue warranties that cover the entire lifetime of a product. Many gadgets for instance come with 1- and 2-year warranties but last much longer (my last Apple MacBook didn’t, but again, that’s another story). “If we went to a longer warranty, there would have to be conditions and usage attached to that,” he said.

How can we be sure that the bulb will last for 17 years or that my 25-year bulb will actually last a quarter of a century? Why is it that some brands of bulbs are conking out quickly?

Much of a bulb’s longevity depends on “how well the electronic components are put together” and “how well it dissipates heat,” noted Eftekhar, who added, “I’d like to see that there are clear cut standards.” LED bulbs include circuitry that cuts voltage way down from 110-volts and 220-volts to around 5-to-12 volts, and that converts household alternating current to direct current. The components also include heat sinks.

His comments echoed explanations by other LED experts and entrepreneurs at a panel discussion at the Cleantech Forum Amsterdam last week who noted that LED bulb failure tend to stem from components other than the light-emitting diode itself.

Even a bulb’s efficiency – industry tends to rate them at both 80% and 90% more efficient than incandescent – can vary with the quality of construction and components. Efficiency can also vary with the phosphor applied to a bulb. Room bulbs such as the new 75-watt EnduraLED are coated with phosphor (that’s why they’re yellow when turned off) that converts a blue diode’s light into visible white light, and that also warms up its Kelvin rating (vendors have more work to do to improve the warmth of the light). Directional LEDs tend use phosphor closer to the diode, which can undermine efficiency.

I like the chances of an LED lighting future. These things have so much going for them besides energy efficiency that should easily accomplish a 2012 U.S. regulation mandating 25% improvement. For people who can afford the upfront cost of $45, LEDs should indeed offer a lower cost of ownership if they last 17 years, and slash energy consumption. As Eftekhar notes, “They are not just consumables.”

They can also help grow crops faster and with less land. They’re easy to control remotely – the Dutch town of Tilburg has installed LED streetlights that brighten as people and traffic move below them and then dim again. The potential for lighting highways, towns and cities is enormous. The controls even allow users to change a light’s color remotely, which has all sorts of possible uses in health and education, as different light waves stimulate learning, healing and behavior.

As for how long a bulb lasts, we’ll have to wait and see. I installed one of my new 12-watt LED bulbs at home 5 days ago. It’s one of the European models rated at 25 years. I’m happy to report that it’s still blazing away, although my usage has totalled a whopping 2 hours. I’ll have to wait 25 years (or is it 15? or 17?) or 24,998 hours before I can issue a full report. I'll instruct my computer to flag me on May 16, 2036, to revisit the subject. I’ll get back to you then - if my laptop outlives its warranty, that is.

Photo: Philips

Note: An earlier version of this post erroneously stated that the 75-watt bulb is the most common in the U.S. It is, in fact, the second most common, after the 60-watt bulb, as the story now states.

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Mark Halper

Contributing Editor

Mark Halper has written for TIME, Fortune, Financial Times, the UK's Independent on Sunday, Forbes, New York Times, Wired, Variety and The Guardian. He is based in Bristol, U.K. Follow him on Twitter. Disclosure