The annual sign-up window for Affordable Care Act plans, which offer health insurance to millions of Americans who do not receive it through work, opened this week in most states. And the good news is that temporarily expanded federal help is expected to keep monthly costs manageable for many people next year.

“There’s good affordability this year,” said Cheryl Fish-Parcham, director of access initiatives at Families USA, a health insurance advocacy group.

More generous help with monthly insurance premiums was first offered as part of the federal government’s pandemic relief program, and the Inflation Reduction Act extended it through 2025.

The current sign-up period for Affordable Care Act plans could be one of the busiest, said Cynthia Cox, director of the Affordable Care Act program at KFF, a nonprofit health research group. That’s in part because enrollment this year reached a record 15.7 million, and also because pandemic enrollment safeguards for people covered by Medicaid, the federal-state health program for low-income people, have expired. Many people who are losing Medicaid coverage are expected to seek alternative insurance on the marketplaces.

Four out of five customers on HealthCare.gov, the federal Affordable Care Act insurance marketplace, will be able to find coverage for $10 or less per month after subsidies, according to the government. Premiums vary, but the situation should be similar at many of the marketplaces run by 18 states and Washington, D.C., Ms. Cox said.

“If you applied a few years ago and didn’t qualify,” she added, “it’s worth applying again.”

In general, you are eligible for marketplace coverage if you lack affordable coverage through your job or don’t qualify for government health insurance programs like Medicare and Medicaid.

Unsubsidized monthly premiums — the “sticker” price — for a benchmark silver plan are rising 4.5 percent on average as a result of inflation and greater use of health care services since the pandemic, according to a KFF analysis. (Plans are grouped by metal levels, ranging from bronze plans, which have low premiums but higher out-of-pocket costs, to gold and platinum plans, which have higher premiums and lower out-of-pocket costs.) The average monthly premium for a benchmark silver plan is expected to be about $477 for an individual, and the average lowest-cost bronze plan $364, KFF found.

Most marketplace customers, however, don’t pay those sticker prices, because tax credits lower their monthly cost — to zero, in some cases. Premium tax credits are based on a family’s size and income and the cost of plans in the area. For 2024, people with income up to 150 percent of the federal poverty level — $21,870 for an individual or $45,000 for a family of four — have a zero premium contribution for a silver benchmark plan.

More middle-income people can also qualify for subsidies, at least for now. In the past, someone who earned more than four times the federal poverty level wasn’t eligible for tax credits to lower premiums. But the rules were temporarily tweaked in 2021 to make the income cutoff less abrupt. Now, premiums are capped at 8.5 percent of household income for people earning more than four times the poverty level ($120,000 for a family of four for the 2024 plan year).

You can use KFF’s online calculator to estimate your tax credit and monthly premium.

Marketplace plans also offer help, based on income, for out-of-pocket costs like deductibles — the amount patients must pay before insurance pays. A new HealthCare.gov rule intended to help save people money on deductibles is debuting in 2024. Under the rule, lower-income people who enrolled in bronze plans with high deductibles, but who did not actively re-enroll in the same plan for next year, could be automatically renewed into similar silver plans, with lower deductibles, if they would pay a similar or lower premium.

Their new plan will have the same insurer and doctor network, and members will be notified ahead of time, according to the Centers for Medicare and Medicaid Services, which oversees HealthCare.gov. (People who actively choose to re-enroll in the same bronze plan won’t be switched.)

The Biden administration has continued funding for trained “navigators” who can help shoppers evaluate their coverage options. Brokers, who may earn a commission from insurers for enrolling people, can also provide guidance. Click “find local help” on the marketplace website or call 800-318-2596.

Some states are taking extra steps to keep marketplace plans affordable next year, KFF said. California, for instance, is offering subsidies that eliminate deductibles for many enrollees, and Massachusetts is raising the income limit for extra state subsidies.

Here are some answers to questions about marketplace open enrollment:

How long does marketplace open enrollment last?

The deadline for signing up for 2024 coverage on HealthCare.gov and on some state marketplaces is Jan. 16 (because Jan. 15, the traditional date, falls on a federal holiday). If you want coverage to start Jan. 1, you typically must enroll by Dec. 15. State marketplace dates may differ; New York’s enrollment period, for instance, starts Nov. 16 and ends Jan. 31.

Also, under a special enrollment period prompted by the Medicaid “unwinding,” former Medicaid recipients whose coverage expired between March 31, 2023, and July 31, 2024, can apply for federal marketplace coverage until the end of next July. (State-run exchanges don’t have to be similarly flexible, though they can be if they so choose.) But if you have lost coverage already, “don’t wait,” Ms. Fish-Parcham said. Apply now to avoid going uninsured.

What if my employer offers health insurance but it’s too expensive for me?

In general, if you would pay more than about 8 percent of your income for your employer’s health coverage, it’s considered unaffordable and you may be eligible for a marketplace plan. If the cost of covering just yourself through your job is affordable but covering your entire family isn’t, your family can enroll in subsidized marketplace insurance while you stay on your workplace plan.

What happens to the expanded marketplace help after 2025?

Congress will have to act to extend the more generous federal subsidies or they will end for marketplace coverage in 2026.