HILO — Hawaii County is about ready to make the final step toward energy-efficient street lights.
Next month, the Department of Public Works’ Traffic Division will bring a proposal before the County Council’s Finance Committee to replace the fairly dim low-pressure sodium lights with brighter light-emitting diode versions.
The move, which would involve about 10,000 lights, could cost between $4 million and $5 million in materials alone and take over three years to complete, said Ron Thiel, Traffic Division chief.
But the payback could be significant, he said, since they consume half as much electricity and have a longer life.
“It will save an excess of a million dollar a year,” Thiel said. “The payback on materials alone is about three years.”
The county has already installed 1,000 LED lights around the Big Island as part of a test run. That was paid for with a $500,000 federal grant.
Finishing the light replacement effort, if approved by the council, would be covered almost entirely by the county, Thiel said.
The state Department of Transportation has agreed to provide $500,000 to replace lights on state owned highways, but no other funding sources have been identified, he said.
“This is quite a big step,” Thiel said.
The bulbs would be replaced by county workers.
Low-pressure sodium lamps have been favored by the astronomy community since they fall within a narrow region of the visible light spectrum.
But they also present safety issues for motorists, particularly since they resemble yellow traffic lights and provide less visibility than other bulbs.
The yellow-green LED lights would provide more light pollution, which the county plans to mitigate with a filter and by installing a shield around the fixture to focus as much light downward as possible, Thiel said.
The filters would eliminate all but 2 percent of the blue light emitted from the bulbs, a particular concern to the Mauna Kea observatories. They also reduce the light’s efficiency by 7 percent.
Ron Laub, the University of Hawaii Institute for Astronomy’s light control specialist, said astronomers prefer the low-pressure sodium lights but can accept the switch to the LEDs with the county’s efforts to reduce light pollution.
“I have not heard any major complaints from astronomers yet,” he said.
The shields help, Laub added.
“We don’t want that light going into the sky,” he said.
Thiel said the shields, or cutoffs, increase costs by about 35 percent.
They will also reduce the area of pavement the bulbs can light up. As a result, new poles would likely have to be placed closer together, he said.
The Finance Committee will likely consider the proposal April 16. The full council would discuss it at a later date.
Thiel said his division is also proposing changes to the county code that would allow businesses, such as resorts, to install LED lights. Only the low-pressure sodium lamps are currently allowed.
The amendments would also likely require the energy-efficient lights to be installed in new subdivisions, he said.
Those proposals may not come before the council until late this year.