People who buy their own health insurance already are lining up for a fast and furious start to this year's shopping season.

Open enrollment starts Tuesday for about 250,000 state residents in the state's individual market, which regulators say was on the verge of collapse this summer.

Shopping promises to be stressful given big premium hikes and tight rules on the doctors and hospitals that subscribers can visit. Most insurers have capped enrollment on plans to control costs, meaning policies could sell out quickly.

"This time last year, we were all twiddling our thumbs," said Richard Lett, an insurance agent with LeClair Group, which is based in Woodbury. "This year, we've all got full calendars."

With rates up more than 50 percent on average, tax credits via the state's MNsure exchange will be more important than ever to consumers. An estimated 123,000 state residents won't qualify for the subsidies, but those who are eligible will see tax credits increase in tandem with premium costs.

People eligible for subsidies, in other words, won't necessarily see extra out-of-pocket premium costs, with more expense passed to the federal government.

"Checking to see if you are eligible for financial assistance, even if it didn't pay off for you before, makes sense," said Linda Blumberg, a senior fellow in health policy at the Urban Institute, a Washington D.C.-based research group. "There's most certainly a much higher probability that it's going to pay off for you now."

Cost is just one of the big challenges. There's a chance shoppers who don't act fast won't find a health plan that includes their doctor.

"Our phones are really, really busy," said Maureen O'Connell, president of Health Access MN, a St. Paul-based group that employs health insurance navigators. "We've had to kind of shift our thinking on this and really plan for a large influx the very first week."

About 5 percent of state residents shop in the individual market, which is undergoing sweeping change with the federal Affordable Care Act.

The turbulence doesn't affect the vast majority of Minnesotans who get coverage via employer groups or the federal Medicare program. Even so, health law problems have seized the political spotlight across the country and in Minnesota in the days before the Nov. 8 election.

On Thursday, DFL Gov. Mark Dayton called for spending $313 million on a 25 percent health insurance premium rebate for people who make too much money for federal subsidies. The upper-income threshold for federal tax credit eligibility is 400 percent of the federal poverty line, which next year works out to $47,520 for an individual and $97,200 for a family of four.

Republicans who control the House have called for an immediate tax credit that would be available to individual market shoppers, plus help with out-of-network costs.

Before any such plans are adopted, Dayton would have to call a special session of the Legislature. In the meantime, MNsure officials say they're prepared to connect shoppers with federal tax credits once open enrollment begins.

MNsure plans to have 160 call center workers answering phones on Tuesday, which is more staff than it had at the peak of last year's open enrollment. Last week, MNsure saw increased website traffic, more requests for password resets and increased call volume overall.

"It tells me people are preparing to make a decision," said Allison O'Toole, the MNsure chief executive. "The stakes are high for everyone."

On Wednesday, House Speaker Kurt Daudt, R-Crown, sent Dayton a letter saying he was told the MNsure website was capable of handling fewer than 700 customers at a time. Officials with the state's IT division countered that the website has a much larger capacity, and is prepared to handle the expected surge.

"The website is ready," O'Toole said. "It's stable."

Many in Minnesota have been missing out on tax credits. Currently, about 44,000 people in the individual market receive federal subsidies through MNsure. A state report earlier this year estimated another 100,000 people qualify but haven't been getting them — either because they're unaware, or they regarded the value of the subsidy as too small to worry about.

With premium increases in 2017, the value of tax credits should get bigger. It's also possible that more people could qualify — especially younger adults — given the complex formula for how tax credits are calculated.

"Premium increases are more likely to push younger people and those with relatively higher incomes into subsidy eligibility," Cynthia Cox, a researcher at the Kaiser Family Foundation, said via e-mail.

When health law changes kicked-in during 2014, Minnesota's individual market rates were among the lowest in the country, and they remained below average despite big premium jumps in 2015 and 2016. That won't continue given next year's rate hikes.

A September study by Urban Institute researchers found Minnesota's individual market rates were about 16 percent less expensive than comparable coverage from employers, but that also won't hold in 2017.

"I think you're going to have a mismatch in the other direction," said Blumberg, one of the researchers on the study. "We have to identify the reasons why we're seeing high or fast-growing premiums relative to the rest of the country in some areas, but not in others."

Health insurers say they'll be staffed up for Tuesday's open enrollment launch. Minnetonka-based Medica and Minneapolis-based UCare have launched new website tools to help people better understand tax credits and health plan options that are complex.

Individual market shoppers who don't live in southern Minnesota won't be able to buy a policy that includes the Rochester-based Mayo Clinic as an in-network option. If all health insurers hit their enrollment caps, that will leave HMO products from Eagan-based Blue Cross and Blue Shield of Minnesota as the only option in most counties, even though the health plan doesn't cover all doctors and hospitals.

HealthPartners coverage will only be available in 11 counties in the metro and St. Cloud areas this year, forcing about 9,100 people in outlying counties to find a new plan.

All the shifts started in June when Blue Cross announced it would only sell HMO policies in the market, which means policies are being dropped for about 103,000 current subscribers.

That's a long list of changes, but it's far from complete.

The bottom line is that none of the health insurers in the market will be selling coverage with broad networks of doctors and hospitals like some shoppers prefer. There are good reasons for the change, said Lett, the Woodbury insurance agent. He argues that these "narrow network" products can better coordinate care for efficiency and patient outcomes.

But it all amounts to a big change for consumers.

"Costs are the headline," Lett said via e-mail, "but the biggest change this year is to people's networks."

Christopher Snowbeck • 612-673-4744

Twitter: @chrissnowbeck