With most cities not having a large buffer for their power grids what effect will having a million charging stations added to the grid in such an area as NYC. It would seem this will add a major possibly unplanned for load on all power grids.

 

EV charging station at home

 

To the extent that EVs are charged at night, it will help the power grid balance its load. There is more than enough unused electrical capacity in the grid at night to power a 100% all electric vehicle fleet in the US (that is, ALL gasoline and diesel cars and light trucks being replaced with EVs, assuming no change in total miles driven). To the extent that most of them are charging at night, it just means the grid gets used more effectively, and no additional power plants need be constructed to accommodate the EVs.