Los Angeles entrepreneur Elon Musk has built a multibillion-dollar fortune running companies that make electric cars, sell solar panels and launch rockets into space.

And he's built those companies with the help of billions in government subsidies.

Tesla Motors Inc., SolarCity Corp. and Space Exploration Technologies Corp., known as SpaceX, together have benefited from an estimated $4.9 billion in government support, according to data compiled by The Times. The figure underscores a common theme running through his emerging empire: a public-private financing model underpinning long-shot start-ups.

"He definitely goes where there is government money," said Dan Dolev, an analyst at Jefferies Equity Research. "That's a great strategy, but the government will cut you off one day."

The figure compiled by The Times comprises a variety of government incentives, including grants, tax breaks, factory construction, discounted loans and environmental credits that Tesla can sell. It also includes tax credits and rebates to buyers of solar panels and electric cars.

The electric automaker Tesla has a side business. It's called environmental credits. The electric automaker Tesla has a side business. It's called environmental credits. See more videos

A looming question is whether the companies are moving toward self-sufficiency — as Dolev believes — and whether they can slash development costs before the public largesse ends.

Tesla and SolarCity continue to report net losses after a decade in business, but the stocks of both companies have soared on their potential; Musk's stake in the firms alone is worth about $10 billion. (SpaceX, a private company, does not publicly report financial performance.)

Musk and his companies' investors enjoy most of the financial upside of the government support, while taxpayers shoulder the cost.

The payoff for the public would come in the form of major pollution reductions, but only if solar panels and electric cars break through as viable mass-market products. For now, both remain niche products for mostly well-heeled customers.

Musk declined repeated requests for an interview through Tesla spokespeople, and officials at all three companies declined to comment.

The subsidies have generally been disclosed in public records and company filings. But the full scope of the public assistance hasn't been tallied because it has been granted over time from different levels of government.

New York state is spending $750 million to build a solar panel factory in Buffalo for SolarCity. The San Mateo, Calif.-based company will lease the plant for $1 a year. It will not pay property taxes for a decade, which would otherwise total an estimated $260 million.

The federal government also provides grants or tax credits to cover 30% of the cost of solar installations. SolarCity reported receiving $497.5 million in direct grants from the Treasury Department.

That figure, however, doesn't capture the full value of the government's support.

Since 2006, SolarCity has installed systems for 217,595 customers, according to a corporate filing. If each paid the current average price for a residential system — about $23,000, according to the Union of Concerned Scientists — the cost to the government would total about $1.5 billion, which would include the Treasury grants paid to SolarCity.

Nevada has agreed to provide Tesla with $1.3 billion in incentives to help build a massive battery factory near Reno.

The Palo Alto company has also collected more than $517 million from competing automakers by selling environmental credits. In a regulatory system pioneered by California and adopted by nine other states, automakers must buy the credits if they fail to sell enough zero-emissions cars to meet mandates. The tally also includes some federal environmental credits.

On a smaller scale, SpaceX, Musk's rocket company, cut a deal for about $20 million in economic development subsidies from Texas to construct a launch facility there. (Separate from incentives, SpaceX has won more than $5.5 billion in government contracts from NASA and the U.S. Air Force.)

Subsidies are handed out in all kinds of industries, with U.S. corporations collecting tens of billions of dollars each year, according to Good Jobs First, a nonprofit that tracks government subsidies. And the incentives for solar panels and electric cars are available to all companies that sell them.

Musk and his investors have also put large sums of private capital into the companies.

But public subsidies for Musk's companies stand out both for the amount, relative to the size of the companies, and for their dependence on them.

"Government support is a theme of all three of these companies, and without it none of them would be around," said Mark Spiegel, a hedge fund manager for Stanphyl Capital Partners who is shorting Tesla's stock, a bet that pays off if Tesla shares fall.

Tesla stock has risen 157%, to $250.80 as of Friday's close, over the last two years.

Musk has proved so adept at landing incentives that states now compete to give him money, said Ashlee Vance, author of "Elon Musk: Tesla, SpaceX, and the Quest for a Fantastic Future," a recently published biography.

"As his star has risen, every state wants a piece of Elon Musk," Vance said.

Before his current ventures, he made a substantial sum from EBay Inc.'s $1.5-billion purchase of PayPal, the electronic payment system in which Musk held an 11% stake.

Soon after, he founded SpaceX in 2002 with money from that sale, and he made major investments and took leadership posts at Tesla and Solar City.

Musk is now the chief executive of both Tesla and SpaceX and the chairman of SolarCity, and holds big stakes in all three, including 27% of Tesla and 23% of SolarCity, according to recent regulatory filings. The ventures employ about 23,000 people nationwide, and they operate or are building factories and facilities in California, Michigan, New York, Nevada and Texas.

Tense talks

The $1.3 billion in benefits for Tesla's Nevada battery factory resulted from a year of hardball negotiations.

Late in 2013, Tesla summoned economic development officials from seven states to its auto factory in Fremont, Calif. After a tour, they gathered in a conference room, where Tesla executives explained their plan to build the biggest lithium-ion battery factory in the world — then asked the states to bid for the project.

Nevada at first offered its standard package of incentives, in this case worth $600 million to $700 million, said Steve Hill, Nevada's executive director of the Governor's Office of Economic Development.

Tesla negotiators wanted far more. The automaker at first sought a $500-million upfront payment, among other enticements, Hill said. Nevada pushed back, in sometimes tense talks punctuated by raised voices.

"It would have amounted to Nevada writing a series of checks during the first couple of years," said Hill, calling it an unacceptable risk.