If you take into consideration the manufacture, expected life span, and then disposal of the vehicle, a Prius is one of the worst cars for the enviroment.
Here is the summary...
So Based on the report, it is MUCH better to buy another Toyota product, the Scion xB, which has a 48 cents a mile "energy-cost".
The Prius registered an energy cost average of $3.25 per mile driven over its expected lifespan of 100,000 miles... Ironically, a Hummer...did much better, with an energy cost average of $1.95 over its expected lifespan of 300,000 miles.
You can find your car at this link
And the full 400 page report here...