The city of Philadelphia has a great many plans to reduce its municipal energy consumption in the name of staving off climate change. These include ambitious but clear initiatives like purchasing more renewable energy and driving more electric cars. But it turns out, when it comes to how much the city spends on its own energy bill, the single greatest offender is something both common and taken for granted: streetlights.
Our approximately 100,000 sodium-powered bulbs expense $15 million to light each year. Which is why, after experimentation with some pilot programs starting in 2011 that changed 5,000 sodium bulbs with more energy-efficient LEDs, the city has promised to scale up the whole effort and replace all of its 100,000 streetlights, along with another 18,000 alley lights.
Philly’s been a bit slow on the uptake here — many other areas, like New York City and Chicago, have previously retrofitted their lights. But for once, our measured pace may actually be an advantage. That’s because 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.
In spite of 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 referenced, 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, because in the end, the doctors still endorsed LED retrofitting, so long as cities use less powerful lights. (The AMA suggested lights no more powerful than 3000K, a unit of “color temperature” for which higher numbers 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.)