Here in Seattle, we don't burn coal. Ok I lied, 0.52% of our energy does actually come from coal. But 96% of it is hydro and wind: http://www.seattle.gov/light/fuelmix/
That's a fuel mix to be very proud of. Unfortunately even here, most people in the metro area live outside Seattle city limits, and right across Lake Washington in the burbs the fuel mix is 32% coal, 16% natural gas http://pse.com/aboutpse/EnergySupply/Pages/Electric-Supply.a...
That mix, combined with the fact that grid power is more efficient than ICE anyway, is still very good.
yes, that's one of the things people forget about battery power - it decouples the generation of the energy from the storage. This means that you can switch from burning coal to solar, hydro or wind as an energy source with no changes at all to the car