HARRISBURG — Pennsylvania residents who buy health insurance in the federally run online marketplace that opens next week will pay below the national average.

Also, the state ranks 10th-lowest out of 47 for which data were available, according to figures released today by the Obama administration.

The stage average is $286 a month for a mid-range plan, not including out-of-pocket costs or tax credits that benefit lower-income families, the figures showed. That’s below the $328 national average.

Variables including income, family size, age, hometown and tobacco use could make the premiums dramatically different for people buying in the marketplace, also known as exchanges, which are a key part of President Barack Obama’s signature health care law.

Factoring in tax credits, a family of four in Pennsylvania with $50,000 in annual income will pay an average of $282 a month for a benchmark policy known as the second-lowest-cost silver plan. It would cost $675 without the credits. A 27-year-old in Pennsylvania making $25,000 a year will pay on average $145 per month for the same policy, or $187 before the tax credit.

The federal government is running Pennsylvania’s marketplace because Gov. Tom Corbett declined to host a state-run exchange.

Under the 2010 federal health care law, uninsured Americans are required to have insurance in 2014 or else pay a penalty will be covered in one of two ways. Also, insurance companies may not increase prices for pre-existing conditions, or deny someone coverage because of one.