“Insurers continue to see this as a good business opportunity,” said Larry Levitt, a health policy expert at the Kaiser Family Foundation. “They see it as an attractive market, with enrollment expected to ramp up in the second year.” Eight million people have signed up for coverage in 2014, and estimates put next year’s enrollment around 13 million.

In New Hampshire, for example, where Anthem Blue Cross is the only insurer offering individual coverage on the state exchange, two other plans, both from Massachusetts, say they intend to offer policies next year. Harvard Pilgrim Health Care, a nonprofit insurer with 1.2 million members, said it expected to participate in the exchanges in both New Hampshire and Maine for the first time and to add Connecticut to the mix in 2016.

UnitedHealth Group and Cigna, which were notable in their caution about the exchanges last year, are expected to enter more markets this year. In Washington State, United is among four new insurers that have told state regulators they are interested in offering plans in 2015…

Federal officials said they were heartened by the continued interest from insurers.