In Iowa, my tax preparer and myself are having trouble figuring out what the penalty would be in this situation. Lets say my wife and I, in 2014, made a combined gross $80k with an AGI of $50k. We have family insurance for us and 3 children. Her 61 yr old father lived with us the whole year and made $0 and is no disabled and had no health care coverage. We wanted to claim him as a dependent. We concluded that the fine for us would be around $500 due to being burdened with his ACA penalty tax. Is this accurate?
Anyone you claim as a dependent is factored into the Shared Responsibility Payment. Being disabled and having no income, he should have qualified for Medicare or Medicaid, those would have counted as Minimum Essential Coverage and allowed you to avoid the fee.
Think of it like this, as part of your shared responsibility you got your family covered so you don't pay the fee for them. You however didn't ensure that your "dependent" (father-in-law) was covered too, therefore you owe the fee for him. We all share the responsibility to make sure everyone who can be is covered, on a personal level that means ensuring dependents are covered, for employers it means ensuring employees are covered, for the state and federal governments it means constructing exchanges, regulating plans, and subsidizing health insurance.
NOTE: You are correct in your logic (didn't double check your math).