But Ken Sperling, Hewitt's health care practice leader, said the extra Affordable Care Act costs come as employers are facing the effects of a weak economy, an increase in the frequency of catastrophic claims and a general increase in medical costs.

"Reform creates opportunities for meaningful change in how health care is delivered in the U.S., but most of these positive effects won't be felt for a few years," Mr. Sperling said in a statement about the health cost analysis. "The incremental expense of complying with the new law adds fuel to the fire, at least for the short term."

A Hewitt competitor, Towers Watson & Company, New York, came up with similar results recently when it looked at underlying health care costs.

The average employee contribution at the employers Hewitt studied may increase about 12 percent, to $2,209, and average expected employee out-of-pocket cost total is also increasing about 12 percent, to $2,177.

The out-of-pocket cost total includes co-payments, coinsurance and deductibles.

Preferred provider organization (PPO) plans dominate the group plan market in most states. Hewitt said it expects the cost of PPO coverage to increase 8.5 percent between 2010 and 2011, to $9,408.

Between 2009 and 2010, the average PPO coverage cost increase was 6.3 percent.

To go with the cost data analysis, Hewitt commissioned a survey of 600 large employers. The firm found that some employers will be charging more for spousal coverage, or charging separately for each individual in an employee's family rather than simply providing "employee-only" and "family" coverage. The idea of penalizing employees who fail to participate in health improvement programs is also getting more attention.