As a follow-up to the photometry tests of a variety of retail LED lamp types first documented about one year ago, the US Department of Energy (DOE) has published Caliper Retail Lamps Study 3.2. The DOE’s Pacific Northwest National Laboratory (PNNL) tested 15 LED products alongside halogen and compact fluorescent (CFL) benchmark bulbs for more than 7,500 hours. The Retail Lamp 3.2 report has been entitled “Lumen and chromaticity maintenance of LED A-lamps operated in steady state conditions.” Results indicate superior performance of the LED A-Lamps, although the solid state lighting (SSL) product results varied considerably.
Long term testing was performed on ten samples of 15 LED lamp models and two benchmark lamp models. Lamps were operated continuously with a maintained temperature of 45°C. Measurements from each lamp were recorded on a weekly basis.
As might be expected, the CFL and halogen benchmark lamp models failed catastrophically before the 7,500 hour tests were completed. There were no catastrophic failures among the LED A-lamps. Of the LED A-lamps, three models delivered excellent 99% average lumen maintenance. Two lamp models, however, had an average lumen maintenance of 65% and below (considered a parametric failure by the DOE). Another model was a parametric failure due to substantial color shift.
Significantly, the report reveals that seven of the tested LED models had sufficient degradation at 6000 hours. The DOE has judged that these models will be unlikely to meet the 70% lumen maintenance over rated lifetime threshold set by Energy Star. The typical rated life of LED A-lamps is 25,000 hours.
Overall, the average lumen maintenance performance of all the LED A-lamps looks very good, per LEDs Magazine. The LED A-lamps also did positively in terms of overall chromaticity maintenance. The range of the LED lamp performance was very large though there were relatively few LED models that performed so poorly. Arguably the benchmark lamps outperformed LED lamps over the useful life of the legacy sources, but the average LED results are more than acceptable for the retail market. The best LED products had virtually no chromaticity shift over the duration of the tests.
The DOE pointed out that the A-lamp testing is not directly comparable to real world lighting applications with on-off cycles that could lead to catastrophic failure. The report also notes that the lab did not use the test procedures or methods defined in the LM-84 standard for lumen and color maintenance testing or the TM-28 standard for projecting long-term lumen maintenance. This is due to the fact that the DOE tests were begun before those standards were complete. Therefore, the DOE data is not directly comparable to data gathered or presented by lighting manufacturers based on those standards. It is also worth noting that the lamps tested were purchased in 2013. There have been considerable improvements in LED and retrofit lamp designs since then. The report is useful in drawing general conclusions about LED A-lamp performance but not to be used as a comparison shopping guide.