Federal health officials are prodding Americans who have previously obtained insurance through HealthCare.gov to consider switching plans, saying that most people can find better prices for the coming year if they do comparison shopping.

When open enrollment begins Sunday, more than 4 in 5 existing customers will be able to find insurance for the coming year that has monthly premiums averaging $51 less than what they pay now for the same level of coverage, according to an analysis by the Department of Health and Human Services of 2016 health plans available through the federal exchange.

HHS released the analysis Friday as part of its promotional activities leading up to the third year’s sign-up season for insurance in the federal and state marketplaces created under the Affordable Care Act.

The Obama administration is touting ACA health plans as affordable even though premiums are rising, on average, by 7.5 percent.

The analysis includes all plans being sold in the 37 states that will continue to rely on the federal exchange next year. The data, based on the price of plans’ monthly premiums, does not take into account the cost to consumers of insurance deductibles and co-payments. Both tend to be more expensive in ACA plans than in the health insurance typically available through employers’ health benefits.

“Consumers will continue to have affordable choices in 2016,” said Richard Frank, HHS’s assistant secretary for planning and evaluation.

The administration’s shopping push comes as evidence is emerging that participants in the ACA marketplaces are more willing than other Americans to switch plans — but not as willing as federal officials would like. Last year, about half of the returning customers looked again on HealthCare.gov to find out what plans were available, and about 1 in 3 switched coverage, according to recent federal data.

“Shopping serves to blunt premium increases,” Frank said during a briefing for reporters.

Unlike with other health insurance, the price that consumers pay for a plan sold on the exchanges depends on a wrinkle involving the government subsidies that the ACA provides most people buying such coverage. Under the 2010 law, the size of the subsidy in each insurance market has a benchmark: the premiums in the second-lowest price plan in the rung of coverage known as “silver.” Silver is the second of four rungs — the others are bronze, gold and platinum — each covering a different degree of patients’ health care.

The cost to consumers can vary if they chose the benchmark health plan in one year, but a different plan slides into that benchmark spot the following year and affects the subsidy.

Although officials are cautioning consumers to look out for such changes, their analysis did not include any information about how many people will encounter a benchmark switch for the coming year.

Based on the analysis, officials said that Americans in most states relying on HealthCare.gov will have ample choice of coverage for 2016. On average, consumers will be able to pick from five health insurers in their market, the same number as for this past year. Most insurers are offering several plans.

However, the data shows substantial variation.

Ten states using the federal marketplace will have fewer insurers for 2016, while 11 will have more.

A handful of states “don’t look so good,” said Larry Levitt, senior vice president of the Kaiser Family Foundation, a health-policy organization.