Dominion Virginia Power has added two plug-in electric hybrid cars and two hybrid-powered bucket trucks to its fleet as part of its efforts to determine the impact of plug-in vehicles on electricity demand and to find ways to conserve energy and reduce vehicle emissions.

Two Toyota Prius hybrids have been equipped with recharging equipment and additional high-technology batteries that significantly increase fuel efficiency by providing up to 30 miles of battery-only driving in normal operating conditions before the gasoline engine takes over. Recharging requires about five hours, at a cost of less than 50 cents, by plugging into a 110-V electrical outlet.

"Hybrid vehicles and plug-in hybrid electric vehicles are well-suited to the urban locations Dominion serves," said David A. Heacock, president of Dominion Virginia Power. "We are putting these vehicles through their paces to determine how they perform in our service area. It will be important to determine how they impact the need for additional electricity - especially at peak early-evening hours - if they become widespread."

The U.S. Department of Energy's (DOE) Idaho National Laboratories will analyze the Dominion test data as part of a larger study of modified hybrid vehicles.

Greenhouse gas emissions for the plug-in versions are half those of a standard Prius and about 80 percent less than those of a gas-powered midsize sedan.

Dominion also is operating two hybrid bucket trucks that use battery power both for driving and for operating the bucket. The truck's diesel engine provides power to recharge the batteries and runs far less often than that of a standard truck. These trucks, which produce lower emissions and less noise, have been assigned to Dominion's offices in Northern Virginia.

The new hybrid trucks - and all on-road diesel trucks in Dominion Virginia Power's fleet - operate on a blend of 80 percent diesel fuel and 20 percent biofuel produced in Virginia from soy.

The company uses approximately 1.7 million gallons of biofuel per year in 783 trucks. Lower vehicle operating costs resulting from improved fuel economy and reduced engine maintenance requirements offset the slightly higher cost of biofuel.