This might be true in the future but we aren't there yet unfortunately. This is due to the incorrect assumption that natural gas is a clean bridge fuel. Once you take into account the methane emissions/leaks from natural gas you end up with a fuel just as bad as coal and oil from a global warming perspective. This is due to methane being very dangerous greenhouse gas in the sort term (now - 100yr time period). This plus the emissions required to produce any consumer product like a car probably means for now electric cars not much better than a traditional gas car.
The only way to make these cars truly emissions free is to remove ALL carbon based energy from the chain. That includes car and battery production, charging, maintenance, and disposal. Until you do that your just switching the source of emissions around. The climate system doesn't care if the greenhouse gas comes from a car or a power plant.
The best thing we could do in the short term until we have a 100% green grid is to hold off on buying the car and walk/ride a bike :)
http://www.thenation.com/article/global-warming-terrifying-n...
http://onlinelibrary.wiley.com/doi/10.1002/2016GL067987/abst...