In what could be a milestone for electric-vehicle adoption in the U.S., electrified vehicles make up half of San Francisco-area new retail registrations, reaching that first in March, S&P Global Mobility reported.

It’s the first major American metropolitan area to attain that level of electrified-vehicle ownership and represents more than three times the U.S. level of 16.6%, the research and data provider said.

The San Francisco percentage continued to grow, reaching a new record of 53% in April.

The registrations included both fully electric models and hybrids. Breaking down the registrations between the two, EVs made up 34% of registrations, more than four times the 7.3% U.S. average, and hybrids comprised 15.8%, compared to 9.3% for the U.S.

S&P’s analysis shows that buyers of electrified vehicles in the Bay Area skew financially well off. About 47% have a household income surpassing $200,000.

In an ironic note, the report says that one of the highest zip code penetrations of electrified registrations in the Bay Area is in San Ramon, where oil and gas giant Chevron has its headquarters.

LEARN MORE: EV Supply Outpaces Industry Average