It's "likely to entice healthier enrollees to opt for a less generous benefit package," said Caroline Pearson, a lead author of the study.
The law's tax credits will make low-cost plans more appealing.
By pairing their tax credit with a bronze policy, some younger consumers can bring their premiums down to the range of $100 to $140 a month, the Kaiser study found. Older people can drive their monthly cost even lower — well below $100, and zero in some cases— if they are willing to take a chance with higher deductibles and copays.
It's a trade-off that some consumers unfamiliar with insurance might not fully grasp.
"A bronze plan is a very basic plan," explained Levitt. It "will enable consumers to pay very low premiums up front, zero in some cases. But when they actually need medical care, they will pay higher costs out of their own pockets."
Job-based plans have been shifting costs to employees for some time. In 2009, when Obama took office, 22 percent of workers were in plans with an annual deductible of $1,000 or more for single coverage, according to Kaiser. By this year, the share had nearly doubled, to 38 percent, including 3 out of 5 employees of small companies.
Obama's law largely reflects what's already going on in the marketplace, but Pearson said over time it may accelerate the shift to plans with higher out-of-pocket costs.
Administration officials are pleased with the large number of low-cost options. Health and Human Services Department spokeswoman Joanne Peters said the administration is confident that consumers will be able to compare plans side by side in the new markets and make the right choices for themselves.
Avalere crunched the numbers on premiums filed by insurers in 11 states and Washington, D.C. Kaiser analyzed 17 states and the District of Columbia. Both studies included a mix of states running their own insurance markets and ones in which the federal government will take charge.