In this essay we argue that the concept of affordable health insurance is rooted in a social obligation to protect fair equality of opportunity. Specifically, health insurance plays a limited but significant role in protecting opportunity in two ways: it helps keep people functioning normally and it protects their financial security. Together these benefits enable household members to exercise reasonable choices about their plans of life. To achieve truly affordable coverage, society must be able to contain the overall cost of health care, and health insurance must be progressively financed, meaning that those who are best able to pay for coverage should pay the largest share. While the recently passed Patient Protection and Affordable Care Act (ACA) falls short on both of these counts, we argue that it makes important contributions toward household affordability through the use of subsidies and regulations. The main shortcoming of the ACA is an insufficient protection against burdensome cost sharing, which we illustrate using several hypothetical scenarios. We conclude with recommendations about how to make opportunity-enhancing expansions to the current coverage subsidies.