ThinkAhead,

Your point is valid and, in fact, all countries are moving to greener grids. A recent study indicates how much greening of the grid in the UK has curtailed the carbon dioxide emissions associated with charging an EV. The decreases are both surprisingly large and continuing. Data and graph at the link below.

https://electrek.co/2017/08/28/electric-car-emissions-electricity-generation-goes-green/