With Tesla's market capitalization now greater than those of Ford and General Motors, founder Elon Musk is also adding to his billions.

According to the Bloomberg Billionaires Index, Musk has added $2.21 billion to his net worth this year. The CEO owns roughly 20 percent of Tesla's outstanding shares, which are up more than 40 percent this year. His total net worth is now $12.9 billion, according to Bloomberg's database.

Forbes, which assigns different values to Musk's other assets and holdings, pegs the CEO's fortunes at $15.1 billion. Along with his Tesla shares, Musk owns an undisclosed chunk of SpaceX, his aerospace venture.

In both cases, the Tesla chief is now among the 100 richest people on the planet. Forbes ranks him 70th while Bloomberg puts him at 86th. He is now richer than media magnate Rupert Murdoch and longtime billionaires like private equity chief Stephen Schwarzman.

Musk hasn't been shy about spending his newfound wealth — even as much of it remains tied up in the company's stock. Over the past few years, he's spent more than $70 million to buy five properties in L.A.'s posh Bel Air neighborhood, according to press reports. None of the properties are contiguous, and local realtors say that Musk plans to build a tunnel to connect two of them.

Or perhaps, it could be the world's first residential hyperloop.

Watch: Mossberg on Tesla