We finally get to see the plug-in hybrid version of Toyota’s top-selling Prius next month at the 2011 Frankfurt Auto Show, ahead of the car’s showroom appearance scheduled for early next year.

We say finally as Toyota has been testing near-production ready prototypes in the U.S. for the past year now, and the team at our sister site GreenCarReports has driven it on several occasions already.

Apart from today’s confirmation of its Frankfurt appearance, however, Toyota is yet to reveal any production specs though we already know a few details.

First and foremost, the Toyota Prius Plug-In Hybrid is based on the regular Prius though it features an extended 5.2 kilowatt-hour battery pack, onboard charger and revised software enabling it to travel at up to 60 mph on electric power alone.

The electric only driving range on the prototypes was just 13 miles, however, we’re expected to see a slightly bigger figure on the production version.

2012 Toyota Prius Plug-in Hybrid

2012 Toyota Prius Plug-in Hybrid

Press days for the 2011 Frankfurt Auto Show kick off on September 13. In the meantime, click here for our full coverage of the event thus far.

And for more details on the 2012 Toyota Prius Plug-In Hybrid, follow the jump below.

[Toyota via GreenCarReports]