Preferred provider organization plans continue to be the dominant plan type offered to employees nationally, with 47.2 percent of all employees enrolled in these, which is 4.7 percent more than are in health maintenance organizations and consumer-driven health plans combined.

But CDHPS are especially big in the Northeast, where 28.8 percent of employees are enrolled in them, compared to the Western region where only 15.1 percent of employees are in a CDHP and 29.9 percent are in an HMO.

Total annual cost per employee varies greatly across the country. For example, in the Northeast, an employer's total annual cost for a single employee is $10,808; in the Southeast it's $7,846.

But UBA executives said it's important to measure health plan costs not only nationally, but regionally.

For example, a mid-size firm in Atlanta, where a health plan for a single employee is $409, is $63 per month less when compared against the national average for all plans, but actually $26 per month more expensive than the average when compared with other CDHPs in the Southeast region.

"Further still, compare this employer's cost to its closest peers using a state-specific benchmark, which in Georgia is $419, and it becomes clear this employer's monthly single premium is actually $10 less than its competitors in the state," UBA's report said.