The city of Napa changed traffic-signal lamps to the low-power LED type. Lately, I have noticed that many of the lamps, particularly the green ones, have developed random dark spots as if parts of the lamps are burning out. I thought that these lamps were supposed to last a long time. Did they switch to LED technology too soon, or is this normal?

You know, some dark spots on humans are considered beauty marks. Maybe the stoplights have beauty marks, too. Ah, who am I kidding? Those are moles.

Bob Quinn, electrical division manager for the city of Napa, said the city switched from incandescent lights to LED lights in phases, with the red lights replaced about nine years ago and the green ones about six years ago.

LED (light-emitting diode) lights last significantly longer than do incandescent lights and also help save money. While incandescent lights last one to two years, an LED light can last anywhere from five to 10 years, depending on the quality of the LED light, according to Quinn. Additionally, incandescent lights have a wattage of 100 while an LED light may be 20 watts (reds) or 12 watts (greens). That means they burn less electricity and are more cost-efficient.

PG&E highly encourages the use of LED lights and offered the city rebates on the purchase of them. After making the switch to LED on the red lights, Quinn said, the city saw a 30 to 33 percent savings on its PG&E bill. (Wow!)

LED lights are wired in series and pieces. The aforementioned dark spots are a result of parts of the lights going out in them. Quinn said the city bought a batch of bad lights, which are most likely the ones showing the dark spots. Once a third of an LED light is out, it is replaced. Priority is also given to overhead signals, as they are the ones most paid attention to, said Quinn. Yellow lights are last in line since they aren’t on as long as red or green lights and use less power. He added that the quality of LED technology, even within the last 18 months to two years, has improved significantly. PG&E has found the best LED lights and continues to research ways to further improve LED technology, such as keeping heat away from the lights, since that damages LEDs. Once LEDs are tested and approved, PG&E once again will provide rebates to replace lights on traffic signals and street lamps.

Technology, you light up my life.

What is Glad You Asked?

Glad You Asked attempts to answer readers’ questions. Lights on but nobody home? Send your questions to me at dmontanez@napanews.com or call me at 256-2224.