Why LED Bulbs Don’t Always Live Up to the Hype About Their Life Spans

The lights, touted as lasting far longer than their incandescent counterparts, can burn out more quickly in some circumstances 

By Jo Craven McGinty. Excerpts:

"According to the U.S. Department of Energy, LEDs use at least 75% less power than incandescent bulbs and last up to 25 times longer.

But it’s not clear how long the modern lights last outside of ideal laboratory conditions, and in certain circumstances, they might not outlive the traditional bulbs they bumped off the shelf.

“A lot of expectations have been created that if you buy an LED lightbulb, you don’t have to change it ever,” said Nadarajah Narendran, director of research at Rensselaer Polytechnic Institute’s Lighting Research Center. “It’s time for us to reset those expectations.”

When an incandescent bulb burns out, it extinguishes with a pop as its glowing filament snaps.

Light-emitting diodes—the components that provide illumination in LED bulbs—are different. Instead of experiencing sudden death, they grow dimmer over time, and according to industry standards, their useful life is over when their brightness is diminished by 30%.

There’s no convenient way to measure this at home. If a bulb no longer seems sufficiently bright, it might be time to replace it."

"According to Dr. Narendran, in keeping with standards established by the Illuminating Engineering Society, the ambient temperature in the lab is 75 degrees Fahrenheit, and the LED packages operate continuously, without being switched on and off, for 6,000 hours."

"But in ordinary use, as many as a dozen LEDs might be connected in a series inside a lightbulb; one or more bulbs might be enclosed in a light fixture that inhibits air circulation; and the lights might be turned on and off multiple times a day—all conditions that can cause LEDs to grow dimmer more quickly than promised."

"If testing procedures were revised to account for all of these conditions, it would alter the longevity estimates.

“You would find LED lifetime is not 20 years,” Dr. Narendran said. “It would be much shorter. It could be worse than an incandescent lamp in some cases. You could get only 500 hours if you have three bulbs trapped in a surface-mounted fixture” where airflow is restricted.

In comparison, incandescent bulbs are expected to last 1,000 hours."

"LEDs have the potential for the longest useful life of all lighting technologies.

But, they said, instead of rating LED bulbs on the length of time it takes a single component—the light-emitting diodes—to degrade, the industry needs to define “LED system life” and develop a corresponding test to accurately estimate its length."