I have a similar, though not quite the same, concern. I wonder if it would be better, instead of outright banning gas powered cars, to tax the emissions. If by some magic we could get 150mpg cars, that could be competitive with a relatively green grid. Or alternatively if mileage can't go up but it's possible to recapture some of the carbon before it leaves the tailpipe - that could also cut down the emissions, achieving the same climate goal.
That said challenges with any such regime:
- it's probably easier to tax the gas directly than the released emissions
- it's definitely a problem to be raising the cost of living for lower-income Americans, who already don't have wiggle room in their budgets
It's pretty likely that EVs will get cheaper over time, as production of them reaches better economies of scale which get optimized more with each new generation. How much cheaper of course is the big open question that remains to be seen, but some European countries have already seen mass adoption as the EVs get cheaper than ICE vehicles (Norway in particular, via a subsidy: https://www.vox.com/future-perfect/23939076/norway-electric-...). That said it's not yet the case that EVs can be made cheaper without policies shifting some of the cost.
One partial answer may be extending cheap credit for buying EVs, as EVs should have cheaper maintenance in the long run and can have cheaper operating costs (though... that depends on the local price of energy, which we don't seem to be great about keeping under control) so it appears the bigger problem with EVs is upfront cost rather than total cost of ownership - a problem better credit could smooth over. Of course this then gets tied up with the problems of interest rates. <nervously glances at the Fed>