Sick Americans in many states and older people could see costs spike under the House-passed Obamacare replacement plan, the nonpartisan Congressional Budget Office said Wednesday.

The CBO estimates that the American Health Care Act will lead to 23 million more uninsured people in 2026 than under current law. It also finds that average premiums will generally fall, though whether states decide to take waivers allowed under the plan will affect how much the costs change.

The new plan allows states to waive current Obamacare rules that mandate what's covered and bar insurers from charging less-healthy people higher prices. Less-healthy people in some of the states that obtain those waivers could face higher premiums and find it tougher to afford coverage after 2020, according to the CBO.

The CBO wrote:

"In addition, premiums would vary significantly according to health status and the types of benefits provided, and less healthy people would face extremely high premiums, despite the additional funding that would be available under [the House plan] to help reduce premiums. Over time, it would become more difficult for less healthy people (including people with preexisting medical conditions) in those states to purchase insurance because their premiums would continue to increase rapidly."

The report estimates that premiums "would decline, on average" for people in the individual health-care market in states that choose to "narrow the scope" of so-called essential health benefits. But the people in those states who use those services could see "substantial increases" in health-care costs.

That could affect people on the individual market who use services such as "maternity care, mental health and substance abuse benefits, rehabilitative and habilitative services and pediatric dental benefits," according to the CBO: