An HSA is a bank account where you can shelter money and/or use it to pay for medical expenses. You open the account and it comes with a debit card or checks. There is an upper limit as to how much you can deposit each year into the HSA. In 2018 that upper limit will be $3450 for an individual, $6900 for a family. If you are over age 55, you can put in an additional $1000 each year. If you don’t spend the money, you keep it and can even invest it. Any earnings on the HSA account are tax-free.
You can use it to pay for any type of medical expense that would qualify for a tax deduction, so more things than are typically covered by insurance. You can use the money for any medical expense for yourself or a dependent, even if the dependent is not covered by the same insurance plan (so, for example, a kid attending college in another state who has separate coverage through the college). You have to have an HSA-qualified health plan in order to create the account, but you are not obligate to deposit money into the HSA or even create one if you don’t want to – but having the HSA is very, very nice.
After you are age 65, you can withdraw the HSA money without penalty. Or leave it. Or use it to pay for your medicare premiums… whatever.
Also, all funds that you put in an HSA are fully written off as a federal tax deduction that reduces your AGI. So if your AGI would be $80,000 but you put $5000 into the HSA, then your AGI is $75, and your taxes will go down by whatever your marginal rate is.
In past years in California insurance policies and off exchange were priced equivalently, but this year Covered California is allowing insurance companies to sell a separate off-exchange silver policy without the surcharge to pay for the CSR money that Trump won’t pay. That’s probably around a 15% discount. Basically, everyone who buys silver on-exchange is pitching in with premium dollars to provide the extra benefits to the poorest group of buyers, but everyone who buys silver on-exchange should also be eligible for subsidies – so all those extra premium dollars are paid by Uncle Sam.
If the reason that your oldest daughter doesn’t qualify for subsidies is that she earns too much, then an HSA is a really good way to shelter money just like an IRA. Just one more way that she can sock away money for the future. So if she can afford it, great idea for a young person. Because the unspent dollars can grow over time, but they always will be readily available to pay for medical expenses. So lets say a young single person age 26 deposits the maximum each year, and after accounting for current medical expenses, is able to save $2500 on average. Ten years down the line, age 36, there’s $25,000 sitting in that account Now lets say at that point the young single person is married but having difficulty conceiving. Her insurance won’t pay for fertility treatment - but the HSA has enough funds to pay for at least one round of treatment. Here’s a good article with examples of things an HSA can be used to pay for - https://www.valuepenguin.com/surprising-benefits-savings-of-health-savings-account
So there really isn’t a good reason for a young person not to have an HSA, assuming they have the money to fund it and don’t have employer-provided insurance. (Some employer do provide HSA options, in some cases with extra dollars to fund the HSA)