The U.S. Department of Energy's CALiPER program has released another special report on LED lamps that are available through the retail marketplace and targeted toward general consumers. CALiPER Retail Lamps Study 3.2 focuses on lumen depreciation and color shift in a subset of 15 LED A lamps from CALiPER Retail Lamps Study 3. The lamps were monitored in an automated long-term test apparatus for more than 7,500 hours.

Ten samples of each lamp were operated continuously at an ambient temperature of 45°C, with measurements recorded weekly. On average, the lumen maintenance of the LED lamps was better than either of the benchmark lamps (CFL and halogen), but there was considerable variation from lamp model to lamp model. In addition to three observed parametric failures (two from insufficient lumen maintenance and one from excessive color shift), almost half of the products failed to meet ENERGY STAR^® early-life thresholds for lumen maintenance, which for seven products was sufficiently low at 6,000 hours that they were unlikely to have lumen maintenance above 70% at their rated lifetime (usually 25,000 hours).

Given the methods used for this investigation, the results should not be interpreted as indicative of a lamp's performance in a typical environment, nor should they be used to discredit manufacturer lifetime claims. A key takeaway is that the long-term performance of LED lamps can vary greatly from model to model, although the lamp-to-lamp consistency within a given model is relatively good. Further, operation of LED lamps in an enclosed luminaire (or other setting involving high ambient temperatures) can induce parametric failure of LEDs well before their rated lifetime; manufacturer warnings about such conditions should be followed if performance degradation is unacceptable.

For more details, see the full report.