Federal regulators opened the federal exchange Healthcare.gov for consumers to browse for plans on Monday, as they announced that rates will be up 25% for the plans for which the tax subsidies are calculated.

The Department of Health and Human Services also warned that more than one in five consumers using the site will only have one insurer from which to choose coverage.

As concerns grow about much higher rates in many states, officials emphasized that the vast majority of people shopping on Healthcare.gov will pay less than $100 a month for premiums when tax credits are included. More than 70% of people will pay less than $75 a month after tax credits.

Healthcare.gov handles individual insurance sales for those who live in the 38 states that don't have their own exchanges.

On average, consumers will have 30 plans to choose from and the average insurer has 10 plans for sale. HHS officials briefing reporters Monday reminded that most people will employer-provided insurance have few far choices than those shopping on the federal exchange.

HHS said earlier this month that about 2.5 million people eligible for tax credits to lower the cost of their premiums are missing out, because they are buying their insurance through insurers or brokers instead of the state and federal exchanges. The Kaiser Family Foundation announced last week that about 5 million people who are uninsured could get financial assistance to cover the cost of their insurance.

Even those who weren't eligible for tax credits in the past should apply again, because they may qualify now that many rates are much higher, said HHS spokesman Kevin Griffis.