Probably because Santa Clara County has more EV sales compared to its neighbors, according to this map:
https://www.energy.ca.gov/data-reports/energy-almanac/zero-e...
And newer cars get driven more than old cars on average so 1/20 cars being EVs will do more than 1/20th of the miles.
And newer cars get driven more than old cars on average so 1/20 cars being EVs will do more than 1/20th of the miles.