By Amina Niasse

NEW YORK, Sept 10 (Reuters) - One in seven Americans have signed up for health insurance coverage through Affordable Care Act marketplaces since their 2014 launch, according to data released on Tuesday by the U.S. Department of the Treasury.

A total of 49.4 million Americans have signed up for the plans, often referred to as Obamacare, with enrollment reaching a high of 20.8 million people in 2024, the agency said.

The insurance plans, run by companies including CVS Health's Aetna and UnitedHealth Group , provide income-based subsidies and are sold on the federally-run Healthcare.gov website or are offered directly by states that run their own sites.

Marketplace coverage since 2014 has been higher in states that have not expanded Medicaid programs under the ACA or did so later, the report said.

Typically, people with annual incomes between 100% and 138% of the poverty level - currently set by the government at $15,060 for individuals and $31,200 for a family of four - are covered by the ACA Marketplace in non-expansion states, versus Medicaid in expansion states.

Florida, Utah and Georgia, for instance, topped marketplace enrollment by percent of population with an average of 20% of residents, compared with 12% of residents in states that expanded Medicaid coverage. Data cited in the release was collected by the Internal Revenue Service from tax forms and other sources.

The average cost of premiums for a year of enrollment in a marketplace health plan fell to $800 through the Biden administration's four years, a senior administration official said.

“Marketplace enrollment has surged under the (Biden)Administration, which has especially helped American families with their monthly bills and entrepreneurs who are looking for coverage as they start new businesses," said U.S. Secretary of the Treasury Janet Yellen in a statement released on Tuesday.

(Reporting by Amina Niasse Editing by Bill Berkrot)

((amina.niasse@thomsonreuters.com;))