According to the reports from the U.S. Department of Energy (DOE), the LED lamp from Philips that won the L Prize in the 60 W replacement category has shown no reduction in light output after 25,000 hours of continuous lumen maintenance testing.

The prize was awarded in August 2011. DOE has tested 200 Philips lamps for 7,000 hours in a specially constructed high-temperature (45° C) facility, so it predicted the Philips lamps would keep lumen maintenance of 97.1% at 25,000 hours. Even though this far exceeded the competition’s 70% requirement, DOE’s intention was to continue testing the lamp for much longer time.

When 25,000 hours of operation was reached on April 29 of this year, none of the Philips lamps had failed, and the average lumen maintenance of the samples was the same as the initial output. What's more, the color was stable, with the chromaticity change on the International Commission on Illumination (CIE) 1976 color diagram found to be less than 0.002 after 25,000 hours—well within the competition's tolerance of 0.004 at 7,000 hours of operation. These results show that well-designed LED integral lamps can operate very reliably over long periods of time, with excellent lumen and chromaticity maintenance.