Satisfaction with hybrids also extends to mass transit.

Officials with O'ahu Transit Services, which runs the bus operation for the city, are so pleased with the 50 hybrid electric-diesel buses purchased since 2004 that they hope to gradually convert half of the fleet to hybrid by 2013.

O'ahu Transit Services president Roger Morton said the city has ordered 10 articulated 60-foot hybrid buses to replace 1993 40-foot vehicles early next year. He said according to a projected bus purchasing plan, about half of the city bus fleet — which now includes 525 buses — should be hybrids by 2013.

The city's first 10 hybrid buses, which have a 75-passenger capacity and began operating in late 2004, cost $749,000 each. The buses initially cost about $200,000 more than standard buses, but the differential has since decreased, Morton said. He said the hybrid buses save up to 33 percent in fuel costs compared with standard buses.

Besides the fuel savings, hybrid buses have better brake life, provide a smoother ride, are quieter and release less emissions into the environment, Morton said.

"Our operators, our mechanics and our customers all like the hybrids and for different reasons," he said. "The operators like them because they are very responsive as a vehicle, they accelerate fairly well. The customers like them because ride quality is better. Mechanics like them because they're very reliable."

The buses had a few glitches before. OTS temporarily pulled its 10 new hybrid electric-diesel buses out of service in October 2005 following an engine fire in one of the buses. Morton said that problem was fixed by the manufacturer and that there haven't been any similar problems since.

Wayne Yoshioka, director of the city Department of Transportation Services, said one issue officials are keeping an eye on is replacing the battery pack for a hybrid bus — which Morton said currently costs about $25,000 — as well as recycling it.

"Come seven, eight years down the line, we're figuring that we're going to have to swap out the battery pack," Yoshioka said. "We know we're saving money on fuel, but the thing that we're still researching, and I don't think the manufacturers have an adequate answer quite yet, is how much is it going to cost to recycle the battery packs."

Yoshioka said he's asked OTS for an analysis of the fuel savings for the hybrids.

"But even if we're just breaking even, this is the environmentally responsible thing to do," he said.