There is an interesting map with numbers of registered electric cars per capita in California based on a study done by the Center for Sustainable Energy.

As it turns out, EV density peaks in Santa Clara at an average of 7.38 per 1,000 people (total 13,745 EVs).

Marin is in second place with 5.64 (1,457), while San Mateo and Alameda are fighting for third spot with 4.87 (3,643) and 4.63 (7,311) respectively.

Source: ecomento.com