U.S. DOE report says subjective evaluations of LED floodlights are generally thumbs-up

Washington, DC--The U.S. Department of Energy (DOE) has published the first of four new investigations that extend the findings of a report published last year. The new report, as well as the old one, focus on so-called LED PAR38 lamps, which are in reality a common form of LED spotlight. The new results suggest that many of the LED products compared favorably to halogen benchmarks in all attributes considered, with some caveats.

(Because the report names are long and involved, this paragraph is devoted totally to the names; skip this paragraph if you want. Last year’s report was called CALiPER Application Summary Report 20: LED PAR38 Lamps, while the new report is called CALiPER Report 20.1: Subjective Evaluation of Beam Quality, Shadow Quality, and Color Quality for LED PAR38 Lamps. The new report focuses on a subset of the lamps from Report 20, which were separately assessed by members of the Illuminating Engineering Society of North America.)

Results
The LED spotlights using a single-emitter design were generally preferred for their beam quality and shadow quality, and the ranking of color quality did not always match the rank-order according to the product's color rendering index (CRI). The takeaway: subjective perceptions of an LED light’s color quality can be different that its CRI rankings, which means -- well, what does it mean? Perhaps CRI is not the be-all and end-all of color-perception categorization.

Other key findings:
• Poor color consistency within the beam of LED spotlights, and stray light outside the main beam pattern, were the attributes most likely to be noted by the observers as negative features.
• LED spotlights with narrow-spot distributions were generally viewed as having less-acceptable beam quality than their narrow-flood or flood counterparts, although there was substantial variation in perceived quality within any of the groups.
• For color quality, the observers generally preferred 3000 K (slightly cooler white) LED lamps over 2700 K (warm white) LED lamps.

Although many of the LED PAR38 lamps were ranked higher than the halogen benchmarks, there is room for improvement for even the best-performing lamps. Furthermore, there remains substantial variability among LED PAR38 lamps -- as was also seen among halogen lamps -- which will require buyers to make careful purchases.

The report is available online at www.ssl.energy.gov/reports