As they have conveniently "forgotten" the cost of the electricity to charge the car while it's parked, even that figure is wrong.  Not only will you save no money on 
energy, you will 
also lose the upfront money on the cost of the car 
and the money to replace the batteries in a few years.  Oh, and I wonder how much wear and tear the weight of the batteries will cause on tires and suspension...  
Ah, but the important thing is that it makes the greenies feel good, not that it actually saves anything.   
