"We call it 'Prime' because it represents the best of Prius," said Nathan Kokes, Toyota's brand manager for advanced technologies, explaining the origin of the car's name.

It will also be a big Prius: 2.4 inches longer the traditional Prius, and a scant half-inch wider. It has a 3,362-pound curb weight, which is 168 pounds heavier than the regular Prius. Blame most of that avoirdupois on the larger 8.8kWh lithium-ion battery