CHICAGO — Workers can expect to pay hundreds of dollars more for their health care coverage next year.

In 2011, the combined average of premium and out-of-pocket costs for health care coverage for an employee is projected to climb to $4,386, according to an annual study released Monday by the human resources consulting firm Hewitt Associates. That’s a 12.5 percent increase, or $486, over this year.

Companies, meanwhile, will see their health insurance costs go up nearly 9 percent, to an annual tab of $9,821 per employee, or double the employer’s annual worker tab from nine years ago, according to Hewitt.

“The practical reality is we are now getting to the point where the average employee is costing the average employer $10,000 a year for health care,” said John Vlajkovic, principal in Hewitt’s health management practice.

Overall, health care costs continue to rise 6 percent to 8 percent annually, primarily because of advances in medical technology and the increasing use of medical services by an aging population.

And in the wake of the recession, employment trends also are affecting health care costs: Companies are hiring fewer younger people, so premiums paid by that segment of the working population, which typically uses fewer health services, are not absorbing the costs of older employees who do.

“An older population tends to have chronic conditions like diabetes,” Vlajkovic said. “And when your hiring rates have slowed, you are not bringing in a younger work force.”

Premiums are being affected by the implementation of the federal health care law, but the impact is expected to be minimal.

“Health care reform has added to the cost burden, but that is only an additional percent or two,” Vlajkovic said.

Industry analysts have said the health law could temper cost increases for everybody once the more than 30 million uninsured have coverage because it will spread risk over a larger population. But that will take time. Although several major new consumer benefits started last week, this broadened coverage will not go into effect until 2014.

“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,” said Ken Sperling, Hewitt’s health care practice leader.

“In the meantime, employers continue to struggle to balance the significant health care needs of an aging work force with the economic realities of a difficult business environment.”

Next year, workers are expected to contribute about $184 a month, 12 percent more than they do now. Their out-of-pocket costs will jump, too, rising 12.5 percent, to $181 a month in expenses, which include covering deductibles as well as co-payments and co-insurance for prescriptions and doctor visits.

Workers will get a first glimpse of health care costs during the coming weeks of open-enrollment season, the annual corporate ritual that allows employees to select or change their benefit plans for the following year.

Hewitt’s projections are calculated using data from 350 major employers and more than 14 million health plan participants spending more than $50 billion annually on health care, and they are averaged out per worker. Employees with family coverage tend to pay more, and workers with single coverage tend to pay less.

And because Hewitt’s survey focuses on employers with an average of 16,000 employees, businesses with fewer workers tend to have higher costs than those highlighted in the survey.