Health Savings Accounts provide a triple tax advantage

"Most people don't think of health savings accounts, aka HSAs, as retirement savings accounts. However, an HSA can actually be a better retirement savings account then any IRA or 401(k). That's because HSAs are the only accounts that enjoy a triple tax advantage: Contributions to an HSA are tax-deductible, the money inside the account is exempt from capital-gains and dividend taxes, and the distributions you take from the account are also tax-free if you spend the money on qualified medical expenses. What's more, once you hit age 65, you can spend your HSA money on anything -- not just healthcare -- without incurring a tax penalty (though you'll pay income tax on the withdrawal).

That's why it's such good news that the contribution limits for HSAs are going up in 2018. The new limits are $3,450 per year for self-only HSAs and $6,900 for family coverage HSAs." Thanks to The Motley Fool: https://www.fool.com/retirement/2018/01/11/5-changes-to-retirement-savings-for-2018.aspx