With substantial premium increases coming in some states in 2016, administration officials are expecting that many consumers already in the Affordable Care Act’s networks will have to switch health plans and find new doctors as they scramble for cheaper alternatives. And millions more Americans could be receiving health insurance through health care marketplaces for the first time.

But insurers in many counties are offering such a dizzying array of health insurance plans with so many subtle differences that consumers have struggled to determine which plan is best for them.

“Normal consumers just cannot assess the dollar consequences of their decisions,” said Robert M. Krughoff, the president of the Center for the Study of Services, also known as Consumers’ Checkbook. “Is a $200 deductible with a $10,000 out-of-pocket limit better for my family than a $2,000 deductible and a $4,000 out-of-pocket limit?”

With the Affordable Care Act’s third open enrollment season starting Nov. 1, new features of HealthCare.gov will allow consumers to type in the names of their doctors, prescription drugs and preferred hospitals, and see which plans cover them, administration officials said.