He wore a red-and-black checked flannel shirt to show he was a man of the people, and now Tennessee Sen. Lamar Alexander has a new personal symbol to show off his energy concerns: an electric Toyota Prius modified to operate exclusively on a battery. "I thought I better put myself where my mouth was," he chuckles over the thrill of driving the specially fitted hybrid at a time when Washington is making energy and alternative car fuels a top priority. Naturally, it's black. "Very senatorial," he says. Alexander says he learned of the new battery technology from Watertown, Mass.'s A123 Systems during a hearing. For a $10,000 premium, they fit cars with bigger batteries that allow the vehicles to drive 30 miles on electric power alone. Just plug it in at night and it's off to the races, says Alexander, who says the technology will hit the mass market in just two years. "I can fill up at night for 60 to 80 cents instead of going down to the gas station to fill up for $60 to $80," he says. "If half our cars and trucks were electric, that would be 125 million and that might take 15 to 20 years but would reduce imported oil by 4 [million] to 5 million barrels a day, which is $400 [million] to $500 million dollars less a day we'd be sending overseas," he says.