Don’t have any research on that… but it’s a good point. However, consider drop in LCOE due to renewables, and also the arrival of decent battery systems, it’s likely that by the time periods we are talking about here, most of the charging stations for the vehicles won’t even need to be connected to the grid. This is certainly what Tesla is planning…

http://reneweconomy.com.au/all-tesla-supercharger-stations-to-be-solar-powered-says-musk-55264/