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How Much Does It Cost to Charge an Electric Vehicle? (A comparison at home and on the road, with gasoline)
(www.caranddriver.com)
This is a most excellent place for technology news and articles.
Even if 100% of EV charging was by burning oil/coal, the power plants still manage this with greater efficiency than the internal combustion engine on your car. That means that even at it's worst, it's still way more environmentally friendly to drive an EV.