SACRAMENTO — California lawmakers approved a $400 billion-a-year program Thursday that would completely overhaul how Californians receive their health coverage by creating a single government-run, universal-care system for everyone in the state.

The state Senate approved the bill to create the Healthy California system 23-14, despite many lawmakers acknowledging that significant details remain unanswered, including how the state would pay for and provide care for its 39 million-plus residents. A legislative analysis of the bill warned that the $400 billion-a-year cost estimates “are subject to enormous uncertainty.”

SB562, by Sen. Ricardo Lara, D-Bell Gardens (Los Angeles County), now heads to the Assembly, where it’s expected to face tough opposition. A legislative analysis said that about $200 billion could be raised from a new 15 percent payroll tax, which would require a two-thirds vote from both houses. The other $200 billion could come from existing federal, state and local spending on health care. But the federal government would have to approve any changes to Medicaid funds for the program.

The total cost would surpass the state’s annual budget of $180 billion. Lara said ahead of the vote Thursday that the bill is a work in progress. However, he urged lawmakers to pass the bill to allow him to continue to work on it.

“We know those who do not have access to care have significantly worse health outcomes and are disproportionally people of color and working poor,” Lara said. “It’s time to say once and for all that health care is not a privilege for those who can afford it.”

The bill calls for rebuilding health care in California from a multi-payer system to a single payer “fee-for-service” system, taking the state into unknown territory with unanswered questions about how “enrollees, providers, employers, and the state would adapt,” according to a legislative analysis. The new program would upend the health insurance industry in the state, leaving thousands unemployed, and the state would set aside funds to retrain that workforce.

It would also eliminate premiums, co-payments and deductibles and allow Californians to get health care from any willing provider without referrals.

Anthony Wright, executive director of the consumer advocacy group Health Access, said the bill has a long way to go, but that SB562 “puts forward a compelling vision of what our health system could be, one that is more universal, efficient, simpler, and focused on patients and prevention rather than profits.”

Critics of the bill said the cost would be too much for the state to bear.

“How do we possibly pay for this thing?” asked Sen. Tom Berryhill, R-Modesto, ahead of Thursday’s vote. “This seems to me to be like what we did originally with Covered California and we are going to just figure it out as we go. … We don’t have the money to pay for this.”

Charles Bacchi, president of the California Association of Health Plans, said the bill would cause “dangerous disruptions in health coverage and quality of care” for millions of Californians.