Study: Your All-Electric Car May Not Be So Green
That article has a typical click-bait headline, but it turns out the key word is “may”. It only applies to the states that use coal the most, like West Virginia, Wyoming, Ohio, North Dakota, and Illinois.
Since coal makes up only a minority of electricity production in the nation overall, and since the majority is produced by sources much cleaner than coal (like natural gas, nuclear, and hydro), the conclusions in this article do not apply to the vast majority of the country.
So yes, your electric car may not be so green, but only if you live in one of those six states.
Further reading: New Study Doesn't Say ‘Electric Cars Aren't Green’ (Headlines To The Contrary)
“Since coal makes up only a minority of electricity production in the nation overall”
Coal is still the major source of energy for electricity production at 39%.
http://www.eia.gov/tools/faqs/faq.cfm?id=427&t=3
It should be noted that the entire eastern part of the country is interconnected into a single grid. There's also a Western interconnect, and a Texas interconnect, and even the three major grids should be connected soon by Tres Amigas.
My point: the electricity generator closest to you doesn't necessarily generate the "electrons" that you use. Even if you select a specific power generator (which is possible in Texas), all that generator does is "pour" power into the "river", which you use somewhere "downstream".
(Yes, that's a poor analogy. But, it's close enough for this discussion).
Maybe someone can find the proportions of power generation, by type of fuel, on each grid. But for all practical purposes, the entire US is a reasonable way to aggregate it. And as someone has already pointed out: only about 39% of total US electricity generation is from coal.
40% is a rather significant minority. Some might even call it a plurality.