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A tabloid headline is meant to grab readers’ attention, and this one does just that: “The great LED lightbulb rip-off: One in four expensive ‘long-life’ bulbs doesn’t last anything like as long as the makers claim.”
This is from a recent article in the British tabloid The Daily Mail’s online edition. It gleefully goes on to show that many LED bulbs tested by a user watchdog group did not even reach the EU’s minimum standard of 6,000 hours, despite claims on the packaging of 15,000 hours and even 25,000 hours of life.
In Britain, as in Canada, the United States and the European Union, incandescent light bulbs have been, or are being, phased out (see The light bulb phase out for more information). The Mail Online article clearly plays to a certain amount of user discontent with being made to pay “up to £40” (about US$66) for a single LED light bulb, only to find that the bulbs don’t perform as advertised.
But there is much more to the story than the newspaper’s sensationalist writing would indicate. In the first place, the article’s author says that some of the bulbs “stopped working” before 6,000 hours. Now, from a user’s point of view, a bulb either works or it doesn’t. But there are many ways in which an LED light can “stop working.”
A United States Department of Energy (DOE) fact sheet on solid-state lighting technology puts it this way: “The failure of any LED system component—not just the array of LED packages, but also the electronics, thermal management, optics, wires, connectors, seals, or other weatherproofing, for example—can directly or indirectly lead to product failure. Further, while some LED products will fail in a familiar catastrophic way, others may exhibit parametric failure, meaning they stop producing an acceptable quantity or quality of light.”
source: Department of Energy
In order to give “a complete characterization of the useful life of an LED product,” there needs to be a way to consider each component in the system and the possibility of its failure. At this time, the DOE notes, “there is no standard” by which to achieve this.
Those bulbs reported on in the Mail Online story, the ones that “stopped working,” probably experienced the catastrophic failure of some component or other, and there is, at least for the present, no easy way to reliably predict that. Barring such catastrophic failure, LED lights do not “burn out” the way an incandescent bulb does: they simply lose their brightness and quality of light over time. The rated longevity on the package indicates the time at which the bulb will have lost 30 per cent of its light output. It could continue to work long after this.
The DOE fact sheet tells us that the rated lifetime given by an LED manufacturer is “a statistical estimate of how long a product is expected to perform its intended functions under a specific set of environmental, electrical, and mechanical conditions.” But that rated lifetime is affected by the product’s design, materials, component selection, manufacturing process, and the environment in which it is used. In short, any individual product may fail either before or after the rated lifetime. Again, the rated lifetime is just an average.
This may be a topic that is overhyped by media based on reasonably isolated scenarios. Although the current methods of testing bulb lifetimes is far from perfect, and can be improved, most industry insiders are comfortable with the current rigorous method of predicting performance.
ENERGY STAR (http://energystar.gov/) and LM-80 testing is respected, accurate, scientifically sound and repeatable. Repeatability is a key criterion of any test designed to protect users. Under US Department of Energy test regimens, bulbs are subjected to durability testing based on statistical distribution and averages in controlled environments. If an ENERGY STAR test ascertains an expected life of 40,000 hours, this indicates that on average these particular bulbs will last 40,000 hours across the line of distributed bulbs. In reality, some may last longer, and some will have a shorter lifespan. In some cases, the environment may effect durability, since tests are in controlled conditions, while real world use will have significant variations in environment, temperature, current fluctuations, usage style (i.e. frequency of on/off cycles) and installation conditions.
source: ENERGY STAR
Both manufacturers and the Department of Energy in the US continue to work hard to maintain reliable testing on the aging of LED bulbs. The testing by ENERGY STAR and LM-80 are not easily manipulated. Users can feel reasonably comfortable that, barring some defects in particular bulbs, the LED lamp should average the specified lifespan.
So what are users to do? Can you believe manufacturers’ claims regarding lifetime performance or not? Will the bulb you are about to buy last for as long as it says on the package, or won’t it?
Currently, the highest assurance you would have of claims being reasonably met, would be to consider:
A good practice is to look for lamps specified by architects, interior designers and businesses. Often referred to as “spec grade”, “specification-grade”, or “architectural grade” bulbs—such as Leapfrog Lighting’s line—these lamps are tested to a higher performance level, taking into account not only overall life, but quality of light. Although overall usable life in hours are estimated through rigorous testing, specification grade also ensures even light distribution, reliable color, and consistent quality throughout the majority of the bulb’s life.
Unfortunately, most LED light bulbs purchased in retail stores don’t meet this standard. It will be a while before users can go into a lighting store and purchase LED products with full confidence that they will perform exactly as claimed. Until then, specification-grade LED products designed and built for the more discerning uses of high-end retail and commercial applications are the best assurance of good value for money in terms of a reasonable return on investment over a long period of time combined with high performance.