People buying Obamacare plans for 2015 can expect to pay about 3 percent more on average for the cheapest coverage — a small increase by historical standards — though premium changes vary widely by state.

"Bronze"-level insurance, the least expensive full- coverage plans available, will cost at least $307 a month on average for a 50-year-old nonsmoker next year, according to U.S. data released today and analyzed by Avalere Health, a Washington consulting firm. The cheapest "silver" plans, the category most popular with consumers, would cost the same person $381 on average, a 4 percent increase from a year before.

Premiums for insurance sold under the Patient Protection and Affordable Care Act can be substantially discounted by tax credits, and about 85 percent of customers qualified for that assistance this year. While the increases are smaller than in years past, the cost of coverage under the Affordable Care Act is generally higher than plans predating the law that provided fewer benefits and weren't available to sick people.