Only 5% of the cars sold in California were electric in 2017. https://www.greencarreports.com/news/1112251_electric-cars-now-5-percent-of-california-new-car-sales-report
For the entire US market:
EV Sales
Overall Vehicle Sales
Market Share
H1 2016
64,736
8,642,171
0.75%
H2 2016
93,476
8,905,483
1.05%
H1 2017
90,302
8,459,212
1.07%