Not Just Screwing in a New Light Bulb

LED streetlights cost more up front than incumbent high-pressure sodium, mercury vapor, and metal halide lights. Partly because the technology is changing quickly, long-term performance in real-world installations is also unproven. "There are a lot of unknowns in terms of maintenance," said Ed Henderson, who runs a system of 200,000 streetlights in southeast Michigan as manager of community lighting for utility DTE Energy.

Whereas replacing a traditional streetlight in DTE’s network is typically as simple as unscrewing a dead bulb and screwing in a new one, said Henderson, LEDs can come in a variety of packages, and they're changing all the time. "Like cell phones and flat screen TVs, there's an obsolescence factor," he said. "When we put an asset up there, we want it to be up there a long, long time." The more "one-off" or specialty installations, the more difficult maintenance becomes for a utility managing streetlights on a large scale, he said.

Yet reduced costs for energy and, crucially, maintenance over the working life of LED streetlights (as long as 10 years for some models) mean they can "pay for themselves" in seven years or less, depending on factors like wattage, electricity rates, and labor costs. "As long as the warranty is longer than the payback," said Andrew Brix, energy programs manager for Ann Arbor, Michigan (map), which expects a four- to five-year payback on LED streetlights with a seven-year warranty, "I'm happy."

Ann Arbor has worked to iron out the kinks of LED streetlight installations over the past few years. Back in 2007, the city drew national attention with plans to become the first U.S. city to convert all of its downtown streetlights to LED technology. Replacing 120-watt bulbs with 56-watt LEDs that were expected to last a decade instead of only two years, the project was projected to shrink the city's public lighting energy use by half, cut maintenance costs by about $85,000 per year and save another $15,000 in annual electricity costs, according to Ann Arbor’s estimates at the time.

Two years later, however, DTE was still billing Ann Arbor at the old rates—as though the LED streetlights were using as much energy as their less efficient predecessors. Since the lights weren't (and aren't) metered, charges were based on estimates, which in turn were based on the older technology.

Similar issues halted an LED streetlight project in nearby Jackson, Michigan, last year. Having determined that installing LED lights will not cut electricity bills until the local utility, Consumers Energy, develops a new rate, City Engineer Jon Dowling said Jackson has for the time being dropped plans to pursue the technology.

In Washington, D.C., by contrast, where a $1 million grant from the economic stimulus program, the American Recovery and Reinvestment Act, will support installation of LEDs for more than 1,000 streetlights this year, the District's streetlight utility bills are based on the bulb's wattage. So according to John Lisle, spokesperson for the District Department of Transportation, D.C.'s selection of a 73-watt LED lights to replace a 150-watt high-pressure sodium light, for example, will cut both energy use and costs by about 50 percent.