WASHINGTON — The number of insurers offering health plans under the Affordable Care Act will increase by about 25%, the Obama administration reported.

Seventy-seven new carriers will offer health insurance coverage for 2015 through federal and state exchanges, the government said last month. The next enrollment period for ACA plans runs from November 15 through February 15.

“When consumers have more choices, we all benefit,” said Department of Health and Human Services secretary Sylvia Burwell. “In terms of affordability, access, and quality,” she called the increased insurer participation “very encouraging.”

“It’s a real sign that the Affordable Care Act is working,” she added.

For the three dozen states served by the federal online marketplace, the number of insurers will be up almost 30%, to 248, from 191 this year. Of the 14 states that run their own exchanges, half have reported their expected number of insurers. Participation in those seven states and the District of Columbia is expected to grow by nearly 10%, to 67 from 61.

Participants will include larger insurance companies that had been hesitant to pursue ACA business. Some of the country’s biggest insurers, including BlueCross BlueShield and EmblemHealth, will enter nearly a dozen states this year via ­exchanges.

The biggest increases in coverage choices will occur in states including West Virginia and New Hampshire, where only one carrier had offered plans.

During the ACA’s first year, more than four-fifths of Americans lived in an area that was covered by at least three insurance companies, and 96% could choose between at least two.

The average number of insurers in each area was five, and the average number of plans to choose from was 47. Ten insurers will leave the marketplace next year, though HHS said their exit will not affect ­competition.

In a setback for the law, a federal district judge in Oklahoma ruled late last month that the federal government could not subsidize insurance in the 36 states that refused to set up their own exchanges. Federal appeals courts in Washington, D.C., and Richmond, Va., had split on the issue, which now appears destined to be decided by the Supreme Court.