29 July 2013 – Tests conducted by the US Department of Energy (DoE) on 200 LED lamps that have been running continuously for 25,000 hours (nearly three years) shows they are still operating at 100% lumen output.

These 60 W lamps were manufactured by Philips which said in 2011 it expected to see lumen maintenance of 97.1% at 25,000 hours, based on 7,000 hours testing of 200 samples. When the lamps reached 25,000 hours of operation in April 2013, the results exceeded expectations. Not only were they still running at 100% lumen output, but the colour was stable (with less than 0.002 change in chromaticity according to the CIE 1976 colour diagram) and all of the lamps survived stress tests which had seen off two thirds of the compact fluorescent lamp (CFL) competitors.
 
The tests were conducted at the Pacific Northwest National Laboratory, in a specially designed facility kept at 45°C. The Philips lamp on test has since been superseded by lower wattage products designed to last even longer, and without the yellow phosphor outer surface, which proved unpopular.

The DoE report says “As this marks one of the first public opportunities to confirm actual performance of a high-quality LED product at 25,000 hours, it can serve as an indicator for the long-term potential for a well designed and constructed product, and validate the methods being used for extrapolating and predicting long-term performance.”

The DoE says it will continue to test a subset of the lamps, creating what it says will be the only publicly available, third-party data set of long-term LED product operation.

Its report says, “Depending on how the solid state lighting market evolves, how the technology changes over time, and whether buyers and producers coalesce around well-designed products with strong lumen and chromaticity maintenance performance, these test results indicate it might be possible to pay less attention to lumen and chromaticity testing in the future, saving producers and buyers significant money, and allowing them to shift their attention to other luminaire performance attributes.”