The electric car outsold all models from other luxury brands Porsche, Volvo, Jaguar, Lincoln and Land Rover.
Over those six months, 4,714 new Teslas were registered, topping even conventional luxury models like Lexus GS, at 2,298, and Audi A6, at 1,619.
The Model S, which starts around $70,000 and can climb toward $100,000, has a younger buyer profile than other luxury models, and a wealthier buyer profile than other electric models.
According to analysis from Edmunds.com, 33.2 percent of Model S buyers are 18-44 years old while 50.6 percent are 45-64 years old. More than three quarters of buyers have an annual income over $100,000.
California is the largest state for auto sales, and this year's sales are estimated to rise more than 10 percent over last year. The top-selling new car in the state was the Toyota Prius hybrid, with 33,987 so far in 2013.
By comparison, the nation's top-selling vehicle, the Ford F-Series pickup truck, has only sold 19,887 in California for the first half of the year.
California may be an ideal market for electric cars, and the luxury electric Model S, but Tesla still has to meet nationwide sales goals for the year. Nonetheless, Tesla Motors Inc. saw its stock rise 1.5 percent following the report of California sales.