More than half of employers are expecting to take a financial hit with the implementation of a new federal COBRA subsidy.

Almost 60% of more than 300 employers surveyed during Aon Consulting COBRA web-based seminars say they think the new subsidy will cost them more for benefits.

Of these organizations, 40% expect their overall healthcare costs to increase by up to 5% because of the new COBRA subsidy legislation; another 40% expect their overall healthcare costs to increase by between 6% and 10%.

Fewer (12%) of these employers foresee their healthcare costs rising by 11% to 15%, while just 8% of those survey participants see health care costs growing by 16% or more.

“As employers begin to plan for their 2010 health benefits, they must take the new COBRA subsidy costs into consideration,” said Tom Lerche, Aon Consulting’s Healthcare Practice leader, in a statement. “Most plan sponsors continue to experience a seven-to-11 percent healthcare cost trend rate, so additional costs from this subsidy will impact overall health care plan strategy for 2010.”

Prior to the subsidy’s enactment in February, COBRA costs for many employers ranged between 140% to 160% of COBRA premium. While the new COBRA subsidy will reimburse employers 65% of their COBRA premiums, employers are bracing for the possibility of more COBRA enrollees (due to unemployment) and more costs associated with implementing the subsidy.

Aon and others are suggesting this will impact overall healthcare costs and lead to potentially higher than expected employee contribution rates for health care coverage in 2010. In addition to higher medical plan costs from utilization and adverse selection, plan sponsors will have higher administrative and communication costs, experts suggest.

Lerche said the typical 5% to 10% of former employees who enroll in COBRA could balloon to as much as 18% as a result of the subsidy.