If the Senate version becomes law, insurers could increase premiums for individual coverage by at least 20 percent more than the double-digit increases already under consideration. By 2020, other changes are likely to result in plans with much higher deductibles. People now getting tax credits that allow them to purchase a policy with a deductible of $3,500 would get subsidies for a plan where the deductible would nearly double, without any funding to pay their out-of-pocket costs.



Many people will face a Hobson’s choice, said Craig Garthwaite, a health economist at Northwestern’s Kellogg School of Management. They will have to choose between a plan with a premium they cannot afford or a plan with a deductible they cannot afford.

While lower premiums touted by Republicans could attract healthier people to buy coverage on the exchanges, other changes could still drive up prices, said Mr. Garthwaite, who is a registered Republican. “It could turn out to be higher premiums and higher deductibles,” he said.

One stark difference between the Senate bill and the Affordable Care Act is the decision to drop the mandate requiring insurance. That could inadvertently discourage the youngest and healthiest people from buying insurance, leaving a higher percentage of sicker people with expensive treatments on the exchanges, driving up insurers’ costs.

When Congress debated the Affordable Care Act under President Barack Obama, a major objective was to tackle soaring premiums and steep deductibles that Americans faced in their employer-based plans and when they bought coverage on their own.

On Thursday, Health Secretary Tom Price argued that Republicans needed to pass a replacement for the same reasons. “We’ve got prices going up, we’ve got deductibles going up, premiums going up,” he said in a television interview on Thursday. “We’ve got people that have an insurance card but they don’t have any care because they can’t afford the deductible.”

Some Republican policy experts are not convinced that this bill’s provisions would solve those problems. “Republicans are taking it and going in the opposite direction,” said Rodney L. Whitlock, a former aide to Senator Charles E. Grassley, Republican of Iowa. Mr. Whitlock thinks the bill’s changes in 2020 to allow insurers to offer plans with less generous coverage could lead to policies with “almost assuredly five digit” deductibles — $10,000 or more.