"The fact is that if your employer 401(k) match is low enough and your combined tax savings on HSA contributions is high enough, you'd amass more wealth by making HSA contributions first," he said. "I'm not saying don't contribute to both; I'm saying the math recommends maxing out what you can put into your HSA each year."
Like other savings vehicles, HSAs have both advantages and limitations. There are, for instance, relatively low caps (indexed for inflation) on yearly contributions. For 2016, the maximum contribution is $3,350 for an individual and $6,750 for a family. Those age 55 or older can make an additional $1,000 yearly "catch-up" contribution.
"If you are using an HSA purely as a retirement savings vehicle and not taking advantage of your 401(k), your contributions will not amount to a lot of money and are probably not going to cover health-care expenses in retirement," said Fronstin of the Employee Benefits Research Institute.
What's more, withdrawals from HSAs for anything other than qualified medical expenses are subject to income tax, plus a hefty 20 percent penalty tax. For those 65 and older, non-qualified distributions are subject to income tax, but not the penalty tax.
In addition, some health-care experts argue that HSA-eligible health plans may actually discourage lower-income consumers from getting needed care because of the out-of-pocket costs. In a 2015 survey by the nonprofit Commonwealth Fund, two out of five adults with deductibles representing 5 percent or more of their incomes reported that they avoided getting care, including preventative tests, because of their deductibles.