Senate leaders on Wednesday were putting the final touches on legislation that would reshape a big piece of the U.S. health-care system by dramatically rolling back Medicaid while providing a softer landing to Americans who stand to lose coverage gained under the Affordable Care Act.

Health care costs for Bay Area residents who buy their insurance on the individual market would be more expensive under the Senate’s plan to replace the Affordable Care Act compared to the GOP House plan, according to new county-level projections of premiums and tax credits by the Menlo Park-based Kaiser Family Foundation.

Starting next month, many Californians will be protected against such surprise medical bills from out-of-network providers, also known as “balance billing.”

Senate leaders have released their Obamacare repeal bill, which would slash federal funding for healthcare and could leave millions of Americans uninsured.

The 142-page bill would create a new system of federal tax credits to help people buy health insurance, while offering states the ability to drop many of the benefits required by the Affordable Care Act, like maternity care, emergency services and mental health treatment.

Senate Republicans, who have promised a repeal of the Affordable Care Act for seven years, took a major step on Thursday toward that goal, unveiling a bill to cut Medicaid deeply and end the health law’s mandate that most Americans have health insurance.