A typical family of four with annual income of $60,000 will, on average, receive tax credits totaling $5,570 in 2016, up from $4,850 this year, the administration said.

But some consumers who have recently received renewal notices have been shocked by the decisions they face.

Ms. Greb said she was too upset to finish a letter she got recently from her insurer, Moda Health, that said her “bronze” health plan, for which she pays $213 a month after a subsidy of $175, would not be offered through the exchange in 2016. The company offered her a similar plan that would cost $265 a month if her subsidy stays the same.

The new plan recommended by Moda has a deductible, the amount she must pay for care before the insurance begins to pay, of $5,500, up from $4,250 in her current plan, she said. “People are putting off care because of the expense.”

The Obama administration said nearly nine out of 10 consumers with marketplace coverage would be able to choose from three or more insurers in 2016. That is important, Mr. Frank said, because in insurance and other industries, “competition intensifies when there are three or more firms in a market.”

In general, he said, “places with fewer insurers have higher premiums.”

But the number of choices varies greatly. Consumers in the online marketplace can choose from 17 insurers in Ohio and Texas, 16 in Wisconsin, 15 in Michigan, 12 in Pennsylvania, 11 in Oregon and Virginia and 10 in Florida and Illinois.

But, an administration report said Friday, only one insurer is offering coverage in the marketplace in Wyoming, and consumers have a choice of just two insurers in Alaska, Hawaii, Oklahoma, South Dakota and West Virginia. And that data, current as of Oct. 19, did not reflect the recent collapse of nonprofit insurance cooperatives in South Carolina and Utah.