We won't get all the juicy details about the 2010 plug-in Prius hybrid until next week's Frankfurt Motor Show, but in the meantime Toyota has released a few choice highlights about the car, which will be leased at the end of this year to 500 customers in Japan, the U.S., and Europe as part of a test run.

According to Toyota, the PHEV Prius will feature a lithium-ion battery back (the standard Prius has a nickel metal hydride battery) that recharges from a 230V power supply in one and a half hours. The car will be able to run for 12.4 miles at up to 6 mph on all-electric mode before switching to gasoline-electric power. Fuel economy is somewhere in the 65 mpg range--a 30% improvement over the regular Prius.

An onboard Hybrid System Indicator in the car displays info on the EV battery driving range and battery charge, while an Electro Multi-Vision Screen shows a graphic of a tree turning into a forest as the battery charges--a similar idea to the Ford Fusion's tree-centered fuel efficiency graphic. Toyota hasn't yet revealed how much the PHEV Prius will cost.

The plug-in Prius may not be the first PHEV to market, but it will be important in at least one respect. The Prius has long been one of the top-selling hybrid vehicles in the U.S., and the car has been the top-selling vehicle (out of both hybrids and gasoline-powered cars) in Japan for four months and counting. The Prius was also the first mass-produced hybrid, making its Japanese debut in 1997. It's safe to assume, then, that most consumers think of the Prius as the quintessential hybrid vehicle, and that means the PHEV Prius will be the general public's introduction to the world of PHEVs in general. Rest assured we'll be watching as the car is unveiled next week in Frankfurt.

[Via Green Car Congress]