Seattle City Light will be converting residential streetlights between the Ship Canal and 65th Street to LED streetlights this summer. Switching the approximately 5,000 sodium streetlights in that area to LED will save the city an estimated $295,000 in the first year.

Sodium streetlights burn out every three to four years, Edward Smalley, manager of streetlight engineering for City Light, told the Ballard District Council May 12. Sodium streetlight manufacturers guarantee only that 50 percent of the lamps will still be working after approximately four years, he said.

Smalley said it costs the city $2.5 million per year just to change light bulbs.

LED streetlights will last for 12 years, at which point they will begin to dim but continue to burn and give light, Smalley said.

He said LED streetlights can save 50 percent to 70 percent of the energy used by sodium streetlights.

LED streetlights will not cycle on and off, a complaint many residents have had about the current streetlights, Smalley said.

City Light has been researching LED streetlights for the past five years and started its first pilot project with them in 2007. Smalley said they were surprised at how well that first project worked out.

Since then, the City Light has done trials around the city, including in Capitol Hill and South Park. City Light saw gains in cost-savings and customer service but not in light quality in the first tests, Smalley said.

In Capitol Hill, there was an 85 percent approval mark for the new streetlights, but there were complaints over the quality of the light – its color temperature and color rendering, he said.

Color temperature is the appearance of the light being generated. Color rendering is the way objects look in the light.

LED streetlights produce a white light that is similar to moonlight while the current sodium streetlights produce a warm, amber light.

City Light made the light from the LED streetlights slightly warmer during the South Park trial and didn't receive any complaints, Smalley said.

He said City Light is moving into the rollout phase now that it is comfortable with the light quality.

"We're quite pleased with the way it's looking out there in the field," he said.

The city is targeting 40 percent energy savings from the new LED streetlights. Warming the color temperature hampered the streetlights energy-saving abilities slightly, Smalley said. He said they will probably achieve 50 percent savings in the Ballard area.

Once all city residential streetlights are converted to LED, there will be $2.9 million in annual savings, Smalley said.

The first phase of the switch to LED streetlights will cost $2.5 million. Federal stimulus funds are providing $1 million, and City Light is covering the remainder. The cost of installing LED streetlights on residential streets citywide is approximately $23 million.

The city intended to start the switch in June, but the manufacturer of the city's LED streetlights is behind schedule. Smalley said they will definitely begin the change in July.

City Light is starting pilot projects this year for LED streetlights on arterial streets.