Why one year is the wrong question
Most health-plan comparisons stop at this year: premiums plus what you expect to pay for care. That is a fair question, and the table above answers it line by line. But a plan is chosen every year, and two things about a high-deductible plan with an HSA only show up across many of them.
First, the premium gap repeats. A copay plan that costs $120 a month more costs that every year, and premiums have grown faster than inflation for decades. Second, the HSA is an investment account. Money goes in before tax, grows untaxed, and comes out untaxed for medical care — the only account in the US tax code that does all three. A dollar left in it at 35 can be a lot of dollars at 55.
So this calculator gives every plan's household the same take-home pay to spend on health each year. Whichever plan costs less invests what it saves, in an ordinary taxable account. At the end it asks what each plan really cost: everything it took for health, grown as if invested, less the HSA it leaves. That is the number that should decide.
Why net cost, and not how much you end up with
Holding every plan to the same yearly budget is what makes the comparison fair, but it makes “how much you end up with” a misleading number. The budget is the most the costliest option could cost that year, so it is set by whichever option is worst — not by yours.
Take a couple on two employers' plans, one on Emory's HSA plan and one on Walmart's, compared over 30 years. Going from a rarely-sick year to a sick-often one adds about $386,000 to what that household spends on health. But the costliest option's care rises faster, so the budget every household is held to rises by about $552,000. The household invests the difference, and ends up with about $412,000 more — for being sicker.
Net cost removes the budget: it is what the whole budget would have grown to, less what the household ends up with. That leaves only what the option itself took, so it ranks every option exactly as before, with the same gaps, and it goes up when you need more care.
Why getting sick often changes the answer
Frequent small claims — repeat visits, monthly prescriptions, urgent care — are cheap on a copay plan and full price on a high-deductible plan until the deductible is met. One very large claim does the opposite: every plan stops at its out-of-pocket maximum, so the winner is whichever has the lowest premiums plus maximum, minus the HSA money. The one-year chart shows where those two effects cross for your numbers; the grid shows how compounding moves the line.
Paying from the HSA, or letting it grow
Most people pay medical bills from their HSA as they arrive. That is fine, and it is the default here. The alternative is to pay from your pocket, keep the receipts, and leave the HSA invested: a qualified expense can be reimbursed tax-free at any later date, so nothing is lost but the cash flow. The scenario table always shows the other strategy next to yours, so you can see what it is worth on your numbers.
Switching plans as you get older
Most people need more care as they age, so the plan that is cheapest at 35 is often not the one that is cheapest at 50. Switch on “switch plans part of the way through” and the calculator adds an option: the HDHP for the first years, then a copay plan. You stop contributing when you leave the HDHP — the law only allows it while you are on one — but the HSA does not close. It stays invested and can pay for care on the new plan, tax-free, for the rest of your working life and after it.
Couples
Two people at employers offering the same plans can be covered in up to fourteen ways: each on your own plan in any combination, one plan covering both at its employee + spouse rate, or both on HDHPs and then switching. Spouse rates are often far more than two employee-only premiums — at Emory, $360 a month for Kaiser covering both against $71 each — so adding a spouse to your plan is frequently the most expensive choice. Two HSAs, one each, also mean two employer deposits and two self-only limits.
If your spouse works somewhere else, set “your spouse's plans” to their own employer's and enter that employer's plans — Walmart's 2027 plans are there to start from. Each of you then chooses from your own employer's menu, and either employer's plan can cover you both, which makes up to eighteen ways to compare.
Kaiser and other HMOs
An HMO's low copays come with a closed network: outside emergencies, care has to come from its own doctors and facilities. That is the real trade, and it is not a number. If the HMO wins here by a narrow margin, the network should decide. Some employers offer a Kaiser plan that is HSA-qualified; model it in the HDHP column.
What this model leaves out
Out-of-network care, flexible spending accounts on the copay plans, embedded family deductibles, copays that apply only after the deductible, and anything that is not money. The methodology page lists every formula and every omission.
Worked through in prose: is the HSA plan worth it if you’re healthy?