A new analysis estimates that average monthly premiums for Obamacare plans would climb 74 percent in 2020 from prices under current law.

The analysis from the nonpartisan Kaiser Family Foundation comes on the same day GOP leadership delayed a procedural vote on the healthcare bill because of a lack of support.

The increase of 74 percent for a silver plan, the middle tier of Obamacare plans, is in stark contrast to an estimate from the Congressional Budget Office that said premiums would be about 30 percent lower than the current law.

Kaiser found that premiums for certain age groups and incomes would suffer more. For instance, people 55 to 64 years old would pay 115 percent more under the Senate bill and people with incomes under 200 percent of the federal poverty level would pay 177 percent more than under Obamacare.

"Increases for younger people are modest, and they could lower their premiums if they opt for higher deductible plans," the foundation said.

For instance, a person 18 to 34 would pay $169 for a monthly premium after a tax credit under the Senate bill compared to $145 under Obamacare, a 17 percent change.

However, someone 55 to 64 years old would pay $583 under the Senate bill compared to $310 under Obamacare, Kaiser found.

The reason for the increases is the changes to the premium tax credits that take effect in 2020. Then, Obamacare's tax credit structure would be replaced with a new one in the Senate bill.

The Senate bill's credits revise income eligibility for tax credits, extending eligibility to people with incomes below poverty but capping eligibility at 350 percent of the poverty level, Kaiser said.

The tax credits in the Senate bill also take into account age as well as income. Obamacare's credits take into account only income.

A key change is that the tax credits in the Senate bill cover fewer costs because the legislation pegs the tax credits to a bronze plan instead of a silver plan.

A person who receives a premium tax credit to buy an Obamacare benchmark plan would get a plan that on average would have insurers pay 58 percent of the expected covered costs, which is akin to a bronze plan, Kaiser said. A silver plan, however, forces insurers to cover 70 percent of the costs.

Therefore the tax credits under Obamacare cover more of the healthcare costs than under the Senate bill.

"Lowering the benchmark means that marketplace enrollees could enroll in what is roughly a bronze plan by paying their required income percentage, but that they would need to pay the entire difference in premium to enroll in the silver level plans that are most prevalent today," Kaiser said.

Another key reason for the hikes is the Senate bill would eliminate cost-sharing subsidies for insurers that lower the co-pays and deductibles for low-income Obamacare customers. The bill keeps those payments in 2018 and 2019 but ends them in 2020.

Older people also would have to pay about five times the premium charged to a younger person as opposed to three to one under Obamacare.

To determine the premium increases, Kaiser looked at what Obamacare customers who bought silver plans would pay since that is the most popular option on the exchanges. It also used data from a 2016 National Health Interview Survey and a current population survey from March 2016.

Kaiser also questioned if the reduction in the value of a benchmark plan and the elimination of cost-sharing payments to insurers could force lower-income people to not get coverage under the Senate health bill.

The analysis comes as the Senate GOP's effort to hold a vote this week was nixed.

The new goal for GOP leadership is to reach a deal by the end of the week and then have the CBO score it over the week-long July 4 recess. The Senate would then take up the bill after returning July 10.