How long do LEDs really last?

-February 17, 2016

I was contemplating my own mortality recently, when I realized 2015 passed by in a blur. Ruminating about the loss of yet one more year, I looked at my LED-laden lamp and thought, “Sure, you might last 50,000 hours, while my expiration date is virtually unknown.” But, was this true?

Happy to take the thought process from my own shelf life to that of an LED, I began to wonder if that 50,000, 35,000, or 25,000 hours of use from an LED could possibly be accurate. For one thing, I don’t mark down the date of purchase for my LEDs. Do you?

Most important, how do we know these claims are accurate – and then I was off on a research mission.  A little more than a year ago, the Daily Mail ran an article claiming that 25% of the expensive long-life bulbs came up short on the claims—with some even falling below the European Union’s legal minimum life of 6,000 hours. These were bulbs that claimed between 15,000 and 25,000 hours of use.

The article discussed tests on five samples of 46 types of bulbs by European partners and consumer watchdogs. The test involved turning bulbs on for 165 minutes and off for 15 minutes until failure. The results of the test:

  • Five types stopped working before 6,000 hours
  • Five with claims of at least 25,000 hours stopped before 10,000 hours
  • 66 out of 230 samples failed before 10,000 hours even though claims were for at least 15,000 hours of use

Not a fan of the Daily Mail? What might you believe? The U.S. Department of Energy’s website discusses tests for a variety of bulb types. For instance, it states that, “CFLs are tested according to LM-65, published by the Illuminating Engineering Society of North America (IESNA). A statistically valid sample of lamps is tested at an ambient temperature of 25° C using an operating cycle of 3 hours on and 20 minutes off. The point at which half the lamps in the sample have failed is the rated average life for that lamp. For 10,000 hour lamps, this process takes about 15 months.”

In that vein, how long do you think a bulb claiming 50,000 hours would need to be tested? Try 5.7 years. What it comes down to is that there seem to be no real sure-fire ways to test the long-term performance/viability of the LED.

My first thoughts went to all of the price comparisons for bulbs from the Edison variety through the more recent iterations. Those cost and performance figures seem to be drawn out of the thinnest of air.

The table above is from a DOE report. And, while the estimated useful life of a high-power LED looks awesome, the source of the data is the lamp manufacturer and some are claiming more than 100,000 hours! Foxes and henhouses come to mind.

According to the DOE, “electrical and thermal design of the LED system or fixture determine how long LEDs will last and how much light they will provide. Driving the LED at higher than rated current will increase relative light output but decrease useful life. Operating the LED at higher than design temperature will also decrease useful life significantly.” Ah, but under what real circumstances can we get an accurate life/performance/cost figure that is, well, accurate?

I concede that I may be missing something important. If that’s true, enlighten me (pun intended). It is comforting on some level, however, that I really may outlive my LEDs.

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