Imagine if any California resident could walk into a hospital or clinic — penniless — to see a doctor about whatever health condition was bothering them.

That’s the scenario state senators envisioned when they pushed through SB562 this week, a bill that proposes a universal health system in California that would ensure that every resident would have access to health care, regardless of wealth or employment status, age or pre-existing medical condition.

The $400 billion-a-year proposal would mean that familiar institutions in the health care ecosystem — including insurance giants Kaiser Permanente, Blue Cross and Anthem — could be virtually eliminated in the nation’s most populous state. Kaiser, the state’s largest private employer, said the plan would ban its model of providing both care and coverage.

Many questions about the proposal, including the most pressing — how it would be paid for — remain unanswered. But the measure would upend the health care network in the state, drastically reducing the role of private insurance companies and scrapping the need for consumers to pay premiums, deductibles and co-pays.

Under the proposal, the state would pay for health care services for most of the 39 million residents of California, including preventive care, prenatal services, immunizations, emergency services, surgeries, dental care and prescription drugs. Military veterans who receive care through the U.S. Department of Veterans Affairs would continue receiving their care that way.

But everyone else would fall under the plan, including people who receive health insurance through their employer, those who buy health plans directly from insurers or through the state exchange, Covered California, as well as Medi-Cal and Medicare beneficiaries and the uninsured.

The bill does not directly address who would be considered a California resident, but it would be modeled after residency requirements for Medi-Cal, which require applicants to produce a valid driver’s license, state-issued identification card, vehicle registration, utility bill or other proof of residency.

Consumers would be able to go to the doctor of their choosing and the hospital system of their choosing — and health providers would be authorized to participate in the state-run system. The bill would create a state board to negotiate payment rates to providers, but it is not yet known how those rates would compare with current ones.

Many health policy experts say the single-payer system — single payer because the state government would pay for everything — would be an improvement for consumers over the current insurance system, but that the bill is missing key details about how to implement such a program.

“As far as consumers are concerned, more than likely it would be better,” said Gerald Kominski, director of the UCLA Center for Health Policy Research. “The primary reason is because you’re no longer going to have insurance based on where you’re employed or how old you are or what your income is. Everybody will have the same insurance. It puts everyone in the same boat. That’s the benefit to consumers.”

The looming question that the bill’s author, state Sen. Ricardo Lara, D-Bell Gardens (Los Angeles County), has yet to answer is: How would the state pay for it?

An analysis by the state Senate Appropriations Committee last month estimated that the bill would come with a $400 billion-a-year price tag — half of which could be generated by enacting a new 15 percent payroll tax, and half of which is already spent by federal, state and local agencies on health care.

A second analysis, commissioned by the bill’s sponsor, the California Nurses Association, found it would cost $330 billion a year. The assessment, completed by the University of Massachusetts-Amherst, proposes two new taxes to generate $106 billion in new revenue — a 2.3 percent gross receipts tax for California businesses with at least $2 million in annual revenue, and a 2.3 percent sales tax.

But these analyses merely outline ways the state could generate tax revenue to fund the single-payer system; Lara has not provided details about how the system would be funded.

Private insurers would still have a role in the new health ecosystem, but it would be greatly diminished. The bill prohibits insurers from offering benefits that would be covered by the state, but insurers could still provide supplemental care for services that the state would not cover, such as plastic surgery, Lara’s office said. Consumers could pay for those supplemental services on their own.

“This bill is not designed to help the insurance industry,” Kominski said. “It’s saying one of the primary reasons we can’t afford health care for all Californians is because of the insurance industry. So we’re going to cut them out of the market.”

Kaiser, one of the largest health systems in Northern California, vehemently opposes the bill. In a letter sent to the state Senate Health Committee in April, Kaiser’s state lobbyist, Teresa Stark, called the proposal “counterintuitive and divisive.”

While the bill would probably put private insurers out of business, experts say it is unclear what its impact would be on Kaiser, whose business model is distinct because it provides both the insurance and the medical care for its members as part of an integrated system. Under the single-payer system, Kaiser would have to radically restructure its operations.

“A model like ours that combines care and coverage would not be able to operate under the rigid system proposed in the bill,” Stark wrote. “(The bill) would ban this world-renowned model of collaboration and create significant upheaval for the individuals, businesses and public employers who purchase coverage from us, as well as for our employees.”

Oakland-based Kaiser employs 160,000 workers in the state and covers about 8.5 million Californians.

The bill passed the state Senate with a simple-majority vote Thursday and now heads to the Assembly, where more details are likely to be hammered out in the coming months. If lawmakers create payroll or other taxes to pay for the shift, the bill would need to pass both houses with a two-thirds majority vote by Sept. 15.

Even with supermajorities in both the state Senate and Assembly, intense lobbying around the bill will make it a tough sell, and the state would still need authorization from the federal government to change the way it administers Medicare and Medicaid funds. And, even if that happened, the bill analysis notes that it would take years for the state to create a technology information system capable of tracking all members and medical providers, plus processing payments.

San Francisco Chronicle staff writer Melody Gutierrez contributed to this report.

Catherine Ho is a San Francisco Chronicle staff writer. Email: cho@sfchronicle.com Twitter: @Cat__Ho

Supporters vs. opponents

SB562 would create a government-run, universal-care system for everyone in the state.

Argument in support: California already spends $367 billion on health care expenses each year and with expected savings from the state’s bulk purchasing power, the estimated new money needed to implement single payer is between $50 billion and $100 billion a year, according to a legislative analysis. Californians would no longer pay premiums, deductibles and co-pays and would instead pay for universal coverage through taxes. That could lead to an overall savings for many people who are paying high premiums and deductibles.

Supporters include: National Nurses United, California Nurses Association, California Teachers Association, as well as other union and Democratic groups, and individual city governments like San Francisco, Berkeley and Oakland.

Argument in opposition: Critics argue that a single-payer system would create a government bureaucracy where care could be rationed and costs would be i nsurmountable. Republicans noted that little is known about the specifics of the proposal, even as lawmakers are passing it. Kaiser, the state’s largest private employer, said the bill would end their health care system as they know it, which could mean significant job losses. “The level of payroll deductions, taxes and fees that would be necessary to finance such a system is mind-boggling,” wrote Teresa Stark, state government relations director at Kaiser in the company’s letter of opposition.

Opponents include: Insurance companies, including Blue Cross and Kaiser, business groups, including the California Chamber of Commerce, and the California Taxpayers Association.

— Melody Gutierrez