The initial cost of the vehicle is higher. Also, when you factor in the cost of a replacement battery (5-7 years) at a cost of about $5,000 (about $1000 per year - which pays for a lot of gasoline), I'm not sure if it makes any economical sense at all. You can expect Insurance Rates (Collision) to go up once the companies start to pay for replacement batteries damaged in a crash.
Finally, I agree with Richard. The Federal Government could mandate that all gasoline include at least 15% ethanol. This would have an immediate effect on our demand for oil; oil prices would drop to offset the increased costs of making ethanol. Brazil did it and is one of the few countries in the world today who could declare energy independence.
Alan