The town of Philadelphia has a great many plans to decrease its municipal energy usage in the name of staving off climate change. These consist of ambitious but obvious initiatives like buying more renewable energy and driving more electric cars. But it turns out, when it comes to how much the city pays on its own power bill, the single largest culprit is something both common and taken for granted: streetlights.
Our approximately 100,000 sodium-powered bulbs cost $15 million to light each year. Which is why, after experimentation with some pilot programs beginning in 2011 that changed 5,000 sodium bulbs with more energy-efficient LEDs, the city has promised to scale up the whole effort and exchange all of its 100,000 streetlights, along with another 18,000 alley lights.
Philly’s been a bit sluggish on the uptake here — many other areas, like New York City and Chicago, have already retrofitted their lights. But for once, our measured pace may actually be an advantage. That’s due to the fact many of the early LED installations from the early 2010s had just one setting — hyper bright — and were promptly were met with public outcry as residents complained about blocks now suddenly lit like hospital operating rooms. Technology has since improved to the point that there are dimmer LEDs available.
Despite those improvements, some concerns over LEDs have remained — in large part thanks to a 2016 report from the American Medical Association that suggested certain LEDs, with their blue-light wavelengths, could hurt people’s eyes. Sodium-powered lights, on the other hand, typically fall in the more eye-friendly yellow-light spectrum.
The AMA’s report also recommended, quite ominously, “a long-term increase in the risk for cancer, diabetes, [and] cardiovascular disease” that could be triggered by bright lights disrupting people’s circadian rhythm. But it seems even the AMA thought that was a bit over-dramatic, due to the fact in the end, the doctors still endorsed LED retrofitting, so long as cities use less powerful lights. (The AMA recommended lights no more powerful than 3000K, a unit of “color temperature” for which higher figures signify more blue wavelengths. While most of Philly’s existing LEDs are at the 4000K level, the city is also testing 3500K, 3000K, and 2700K models.)