Pumped hydro is a well established technology with a round trip efficiency ~75%. As for the cars, they can we can install chargers at all parking spots and tak

Pumped hydro is a well established technology with a round trip efficiency ~75%. As for the cars, they can we can install chargers at all parking spots and take advantage of the intermittent energy during the day to charge the cars then. Many colder climates have engine blocker heater outlets as a standard feature for outdoor parking, adding 120V or 240V chargers to new parking spots (and retrofitting old ones) is not a far fetched idea.