Colorado Springs replaced the incandescent bulbs in traffic signals with LEDs. Now, the city has saved a bundle of money and untold kilowatts of electricity in a five-year effort.

The replacement program began in 2003 and is nearing completion on all 561 intersections in the city. Measurements at 14 intersections showed costs declined 74 percent on average, yielding roughly $280,000 in savings.

In recent, the city officials are studying a similar conversion for streetlights at the roughly 40 intersections where streetlights are on the same pole as the traffic signal. Rob Helt of the Traffic Engineering Department said using LEDs in street lights has worked well in other cities, but Colorado Springs is approaching the idea cautiously because the high-tech lights are also costly, they are still evaluating the technology.

Expanding the program beyond traffic signals could pay off if the city's recent experience is an indication. The cost for running traffic signals varies. At Woodmen Road and Lexington Drive, the signals consumed $104.93 worth of energy in January 2006, before the new LED lights were installed, and $27.38 in January this year.

Shane Burns, a physics professor at Colorado College, noted the LEDs replace incandescent bulbs that were essentially the same technology as that invented by Thomas Edison in the 1870s, an incandescent bulb works by driving an electric current through a tiny wire, the wire gets hot and glows. It's an effective but inefficient technology because incandescent bulbs create wasted light in frequency ranges humans can't see, such as infrared. LED lights, by contrast, are made of semiconductor material and emit all their light at a particular wavelength, that means less energy is wasted and less is needed to run the device.

Besides, LEDs also last longer, five to ten years, compared with one or two years for incandescent bulbs. The result is even more savings because crews spend less time replacing the bulbs. On the other hand, the LED lights are more expensive, $35 to $50 each compared with just $3 for an incandescent bulb.

According to a report by the Environmental Protection Agency, Denver began its conversion program in 1996 and later reported annual energy cost savings of $276,000, Colorado Springs' estimated savings isn't much in a $238 million general-fund budget.

The $280,000 savings is about double what the police department will spend this year just on ammunition. City budget director Lisa Bigelow pointed out, still, any opportunity that they have to increase efficiency and getting cost savings is significant for their city.