The study found that 48 percent of families currently buying their own coverage would be eligible for tax credits next year, averaging $5,548 per family, or 66 percent of the average cost of a benchmark “silver” policy offered through new state insurance markets.

“About half of the people won’t be paying the sticker price,” said Gary Claxton, director of the health care marketplace project at Kaiser, an information clearinghouse on the health care system. “The people who get help will get quite a lot of help.”

“Many, but certainly not all, of the people who don’t get tax credits will pay more,” he said. “How much more will be a function of a lot of different things.”