It gets a bit more complicated when your work coverage extends to a family member, like Carter's daughter. In Carter's case, she has to ask her employer how much insurance would cost her if only she were covered. If it's more than 9.5 percent of her income, she meets the test. Then she and her daughter should be able to move to a plan in the exchange. Based on her income, she should be able to find considerably cheaper coverage there.
In a family with adult children under 26, it may also be worth seeing how much separate policies would cost for parent and child, and whether the child might qualify for Medicaid coverage. These options are much more promising when the child is no longer a dependent on the parent's taxes. Also, Medicaid might only be an option in states that expanded the program. Georgia, for one, didn't.
Under the law, children up to 26 can stay on their family's coverage, so there's no need to split it up if it doesn't save money.