With the current Prius PHEV conversions (privately done, not by Toyota), they can run Full Electric (EV) until the battery gets to 20% (30-60 miles) and then the car autmatically switches to ICE.

Once in ICE mode, the car will switch back and forth, as it does now between electric and ICE as the regenerative braking will provide some charge to the batteries.

So basically, with a good PHEV, you could drive 30-60 miles per day on a plug-in charge. The average commute is 24.9 miles per day. This means, you would not use Gas for your daily commute, but if you wanted to drive to Atlanta, you could. Obviously, you would get 150+ MPG for the first 30-60 miles, and then the # would drop from there. On a 200 mile trip, you could expect about 75MPG or less. (obviously this is still up and coming so exact numbers are not available.)

I will touch on Rengenerative Braking in it's own thread.

Charles