KAHULUI, Maui — Maui County is the newest participant in a national field performance test of Toyota Priuses that have been converted to plug-in hybrid electric cars.

Mayor Charmaine Tavares last week gave one of the converted cars a test drive at Maui High School's nationally recognized automotive shop, where work was done to install a 5-kilowatt-hour, lithium-ion battery pack in the Prius' hatchback trunk and a 110-volt charging port on the back bumper.

The program is sponsored by the Idaho National Laboratory and Advanced Vehicle Testing Activity by the U.S. Department of Energy. The converted 2007 Prius was provided to the county at no cost.

The car's standard hybrid system, which uses both gasoline and electricity — sometimes separately, sometimes together — remains intact. The conversion added the 200-pound battery pack and will allow the vehicle to travel solely on electric power for the first 35 miles, said Pat Cadam of Pat's Garage. The San Francisco-based business is doing the conversions for all 120 vehicles that will be involved in the program by the end of the year.

The plug-in Prius gets an average of 60 to 70 miles per gallon compared with 40 to 45 miles per gallon for a standard Prius hybrid, Cadam said.

Data from the car's activities will be collected by remote, wireless means and sent to the Idaho lab for evaluation.

Tavares said the Prius will be used for Meals on Wheels deliveries or other activities that require stop-and-go city driving, to take full advantage of the fuel-saving benefits of the plug-in hybrid electric system.

Maui Electric Co. also is using one of the converted cars, and there are four others elsewhere in the state participating in the national study.

Students in Maui High's award-winning auto shop program watched Cadam and his crew conduct the conversion. The program is led by Neill Nakamura and teacher Shannon Rowe, who is the state's first certified hybrid-vehicle instructor.

The county and the Maui Economic Development Board are partners in supporting the school's automotive program. Tavares said with training in the latest automotive technology, the young mechanics will be able to join a skilled "green" workforce.