As early as 2011, the Municipal Solid-State Streetlighting Consortium (MSSLC) of US Department of Energy (DOE) has conducted a trial on nine SSL streetlights in Kansas City. Recently, DOE released a Gateway report in support of the result of the test that the Municipal Solid-State Streetlighting Consortium (MSSLC) conducted on nine LED-based luminaires relative to high-pressure-sodium (HPS) lights. The report reveals that the LED lights didn't universally best the HPS incumbents in terms of lumen output or efficacy, but the solid-state lighting (SSL) products did generally deliver more lumens to the roadway surface and less light spill. Realize also that the LED products were installed in February 2011 and therefore use technology that is relatively outdated at this point.
The project involved LED lights installed in place of 100W, 150W, 250W, and 400W HPS fixtures. The SSL products ranged from a 63W fixtures used in place of a 100W HPS lamp to a 291W fixture used in place of a 400W HPS lamp. The measured reduction in energy varied from 31–51% with a mean of 39%. But the LED lights also emitted 31% fewer lumens on average.
But the advantage for the LED lights was truly significant in some cases. For example, a 130W LED fixture that replaced a 150W HPS fixture had an application efficacy advantage of 83 lm/W compared to 45.1 lm/W. The report noted that both the LED and incumbent fixtures were in a setting with some spill light from an adjacent source. But in a 250W comparison with no spill light, an LED fixture delivered 47 lm/W compared to 33.6 lm/W for an HPS fixture.
In the 400W category, one LED performed better than the incumbent and one worse. The DOE had also recently released a Snapshot Report on outdoor area lighting that concluded that LED products were in general still struggling to replace 400W incumbent sources. But clearly there are some capable 400W replacements on the market.
Generalizing the results, the Gateway report stated that LEDs are slightly more efficacious than HPS counterparts. But the SSL alternative offers significant energy savings by both eliminating light spill and delivering more effective and uniform lighting with lower overall lumen output.
