New Yorkers will pay less than they used to for individual health insurance under ObamaCare — but they better not get used to it, because steep increases are on the way and the choice of doctors will be limited, critics warn.

While health-insurance costs will balloon around the country under the Affordable Care Act, an unusual legal situation in the Empire State will lower prices when the markets for President Obama’s signature legislative achievement open on Tuesday.

Everyone who doesn’t already have a medical policy — through work, Medicare or otherwise — will have to buy a policy or face fines once ObamaCare begins.

In New York, the new presidential plans can be had for an average of 29 percent less than old individual policies — $356 a month, compared with $500 — experts at the Manhattan Institute for Policy Research predict.

By comparison, the monthly rate for a 27-year-old man in Connecticut will soar 98 percent, to $238. A 64-year-old woman in that state will see her premium surge 83 percent, to $683, an analysis by the institute found.

Lead researcher Yevgeniy Feyman said New York’s situation is “very, very unique” due to insurance-industry reforms signed into law by Gov. Mario Cuomo in 1992.

The state’s “pure community rating” system requires insurance companies to offer policies at the same price, regardless of the purchaser’s age, gender or health.

“This is what destroyed the New York individual market,” where costs are currently among the highest in the nation, Feyman said. “That being said, the rate we [will] have, $356, is not cheap.”

Feyman said his group’s $356 figure for New York is a composite based on the average cost of the “bronze” policies that are the least expensive among four levels of standard coverage: “platinum,” “gold,” “silver” and “bronze.”

Top-tier platinum policies will cost individuals up to $896 a month, the state Health Department’s online estimator shows.

Available tax credits can reduce the price for individuals earning less than $45,960 or families of four earning less than $94,200, limiting their maximum cost to 9.5 percent of annual taxable income.

The complex formulas also offer bigger breaks to residents of Staten Island.

For example, a single Manhattan resident earning $35,000 a year will get a monthly credit of $88, while a single Staten Islander will get a credit of $107.

A Health Department spokesman said the difference was due to the higher price of Staten Island’s second-lowest-cost silver plan.

The penalty for ignoring ObamaCare’s “individual mandate” to buy health insurance next year is $95 per adult and $47.50 per child — up to $285 per family — or 1 percent of taxable family income, whichever is higher.

But it will jump to $325 per adult and $167.50 per child, or 2 percent of income, in 2015, and to $695 per adult and $347.50, or 2.5 percent of income, in 2016, with future hikes tied to cost of living.

Pacific Research Institute President Sally Pipes, author of “The Cure for Obamacare,” said that’s not enough to get healthy, young adults to shell out for coverage.

“Even though the price is down, the price is still very expensive,” she said. “People are not going to buy into this. Then the system will implode.”

Merrill Matthews, a resident scholar at the Institute for Policy Innovation, predicted a “death spiral” in which the rates rise over the next several years, leading healthy people to drop their coverage while “very sick” people “stay in until the very last drop,” forcing rates up even more.

“The death spiral is well known in health insurance,” he said.

Edmund Haislmaier, who studies health-care policy for The Heritage Foundation, said some medical providers will refuse to accept ObamaCare, noting four of the insurers offering policies in New York specialize in Medicaid plans.

“You’re going to have very limited access to doctors and hospitals,” he said.

Danielle Holahan, deputy director of the New York State of Health marketplace, said that officials believe the rates being offered are “sustainable,” and that 330,000 uninsured residents will buy ObamaCare over the next three years, up from 17,000 who buy individual insurance now.

She also said a “network adequacy requirement” for insurers means everyone on ObamaCare will be able to get to a doctor or hospital in their network within 30 minutes on public transportation.