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How many years does it take to test a lightbulb?

Consumer Reports News: June 02, 2011 03:24 PM

How do you test claims that a light bulb will last a generation? Manufacturers say that LEDs can last 25,000 hours—22 years—and even longer, but in our tests, several bulbs didn’t even make it to 3,000. We’re still testing and we’ll publish the results in early September.

LEDs come wrapped in a number of product claims, such as energy efficiency, high-quality color, and a very long life—25 to 50 times longer than an incandescent. But even the U.S. Department of Energy admits that testing these life claims by collecting real-application data over the long term is difficult, in part because new versions come out before the old bulbs are fully tested.

Another challenge is that unlike an incandescent, which fails abruptly, an LED’s light usually fades over time until it becomes too dim for use—that’s when the light’s output has diminished by 30 percent. So if the manufacturer claims the LED’s life is 25,000 hours, the bulb could provide enough light for more than 22 years if used three hours a day. At that point, the light output would be nearly a third less than when you first turned the LED on and should be replaced. But other components within the LED may fail earlier and are often not factored into the life claims, according to the DOE.

Before you buy an LED, check the details of the warranty. Energy Star-qualified bulbs must have a three-year warranty, and some we’ve seen are for five or six years. And be sure to hold on to the receipt—but maybe not for a generation.

Kimberly Janeway

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