PNNL

There are endless jokes that go something like this—how many engineers does it take to change a light bulb? While good for a giggle, these jokes stem from an annoying issue for home and building owners—light bulbs need frequent replacement.

Consumer desire for both efficient and long-lasting lighting products has resulted in continued advancement by the industry. But just how long do today's highly-efficient luminaires perform compared to the products that they seek to replace?

Through the DOE's GATEWAY program, researchers at PNNL recently evaluated the long-term performance of light-emitting diodes (LEDs) through collection of illuminance—or light level—and color data at four sites with LED installations. Where LEDs had been in use for up to 13,000 hours at the time of data collection, the researchers found stable color performance at most sites. While one site found greater color shift than expected, the LED module manufacturer made no claims about color consistency, and the manufacturer was grateful for the field data as it helped them improve their products. The researchers also found that the average illuminance at all sites either met or exceeded Illuminating Engineering Society recommendations.

Sites and Stats

The sites and lighting projects evaluated include:

• Hilton Columbus Downtown Hotel (Columbus, OH): Dedicated LED downlights replaced compact fluorescent lamps (CFLs), resulting in energy savings of 50 percent
• University of Maryland’s Clarice Smith Performing Arts Center (College Park, MD): LED retrofit kits replaced halogen luminaires in halogen wall washers, resulting in energy savings of 80 percent
• Princeton University’s Carl Icahn Laboratory (Princeton, NJ):LED retrofit kits replaced fluorescent luminaires in a 2x2 troffer, resulting in energy savings of 24 percent; LED retrofit kits replaced CFL downlights, resulting in energy savings of 60 percent
• St. Anthony Hospital (Gig Harbor, WA): LED lamps replaced CFLs in downlights, resulting in energy savings of 59 percent

At the Hilton—where 3,700 LEDs were installed in guest rooms—light levels increased by 3 to 7 percent on average. After 14,500 hours of use, less than 1 percent of these LEDs required maintenance or replacement.

At the Clarice Smith Performing Arts Center, only one of 135 modules needed replacement after 17,000 operating hours. University of Maryland previously used halogen lamps with a lifetime of 1,500 hours—lamps that would have already been replaced 11 times within 17,000 hours.

The LED retrofit kits at the Icahn Laboratory continue to show great performance after almost 11,000 hours.

At St. Anthony Hospital, the more than 1,200 LED products met performance requirements after 8,800 hours and the facility staff found the return on investment attractive enough to continue with LED conversions. However, the LED installation required more maintenance than expected, with about 12 percent of the CFL ballasts and 6 percent of the LED lamps needing to be replaced.

The four sites illustrate value beyond energy savings—maintenance savings, easier integration with control systems, and improved lighting quality. For more information, read the report on DOE’s website.