The $3,000-a-Year HSA: Invested for 25 Years vs. Spent on the Deductible Every January

Main by Arron Knight

Every January, the same $3,000 shows up in Clara’s checking account with a job to do. It can pay the deductible on her high-deductible health plan, or it can go into a health savings account and stay there for twenty-five years. The two paths look identical in year one. They are not identical in year twenty-five.

This is arithmetic, not prophecy. I am going to build both paths year by year, state every assumption, and show where the numbers come from. If you rebuild the table in a spreadsheet, you should get the same answer. If you change an assumption, you should get a different answer, and that is the point.

The setup

Clara is 40. She is covered by a qualifying high-deductible health plan with a $3,000 deductible. She has $3,000 a year of spare cash she can direct either to medical bills or to an HSA. She expects to work until 65 and to have medical expenses along the way, but she wants to know what happens if she pays current bills from cash flow and lets the HSA compound.

The HSA is not a normal account. Under IRS Publication 969, contributions by the account holder are deductible whether or not she itemizes, employer contributions are excluded from income, earnings inside the account are tax-free, and distributions used for qualified medical expenses are not taxed. That is three tax advantages stacked on one account. The catch is that the money has to be used for qualified medical expenses, or it becomes ordinary income plus a 20% additional tax unless an exception applies.

The deductible itself is a qualified medical expense. Publication 969 says qualified medical expenses are unreimbursed medical expenses that could otherwise be deducted on Schedule A, and Publication 502 defines medical expenses as the costs of diagnosis, cure, mitigation, treatment, or prevention of disease. A deductible payment to a hospital or clinic is squarely in that category. So Clara can pay the deductible from the HSA, or she can pay it from checking and leave the HSA invested.

Path A: Spend the $3,000 on the deductible every January

In Path A, Clara pays the deductible from her checking account and never funds the HSA. The $3,000 is gone. There is no account, no earnings, no tax deduction, and no future balance. The only thing she gets is the medical care she already needed.

This is not a stupid path. It is the path most people take, because the bill is due now and the retirement account is abstract. But the arithmetic is stark: after twenty-five years, Path A has a balance of $0.

Path B: Fund the HSA and invest it

In Path B, Clara contributes $3,000 to the HSA each January, pays the deductible from checking, and invests the HSA in a broad stock index fund. She does not withdraw for current medical expenses. She keeps receipts, because Publication 969 requires records of distributions and qualified medical expenses, and because she may want to reimburse herself years later for expenses incurred now.

Here are the assumptions, stated plainly:

  • Annual contribution: $3,000, made on January 1 each year.
  • Investment return: 7% nominal, compounded annually. This is an assumption, not a promise. It is roughly the long-run nominal return of a diversified stock portfolio, but future returns will differ.
  • Inflation: 2.5% for general prices. This matters for the real value of the balance, not for the nominal arithmetic.
  • Tax rate on contributions: 22% marginal federal rate. Clara’s $3,000 contribution reduces her taxable income by $3,000, saving $660 in federal income tax in the year of contribution. If she is in a different bracket, the savings change.
  • No state tax, for simplicity. If your state taxes income, the deduction is worth more.
  • No withdrawals until age 65. At 65, Clara begins using the HSA for Medicare premiums and medical expenses, which Publication 969 lists as qualified medical expenses for account holders 65 or older, other than Medigap premiums.

The contribution limit is not fixed at $3,000 forever. The IRS adjusts HSA limits annually for inflation. For 2025, the self-only contribution limit is $4,300 and the family limit is $8,550. Those figures come from IRS Revenue Procedure 2024-25, which is the annual inflation-adjustment notice. I am using $3,000 as a round number that is below the limit in every year of the projection, so the arithmetic is not distorted by limit changes. If Clara contributes the maximum instead, the ending balance is larger, but the comparison between Path A and Path B does not change.

The year-by-year ledger

The table below shows Path B. Path A is not shown because every row would be $0. The “Contribution” column is the $3,000 added each January. The “Growth” column is 7% of the starting balance plus the January 1 contribution. The “Ending Balance” column is the sum.

Year Age Starting Balance Contribution Growth at 7% Ending Balance
1 40 $0 $3,000 $210 $3,210
2 41 $3,210 $3,000 $435 $6,645
3 42 $6,645 $3,000 $675 $10,320
4 43 $10,320 $3,000 $932 $14,252
5 44 $14,252 $3,000 $1,208 $18,460
6 45 $18,460 $3,000 $1,502 $22,962
7 46 $22,962 $3,000 $1,817 $27,779
8 47 $27,779 $3,000 $2,155 $32,934
9 48 $32,934 $3,000 $2,515 $38,449
10 49 $38,449 $3,000 $2,901 $44,350
11 50 $44,350 $3,000 $3,315 $50,665
12 51 $50,665 $3,000 $3,757 $57,422
13 52 $57,422 $3,000 $4,230 $64,652
14 53 $64,652 $3,000 $4,736 $72,388
15 54 $72,388 $3,000 $5,277 $80,665
16 55 $80,665 $3,000 $5,857 $89,522
17 56 $89,522 $3,000 $6,477 $98,999
18 57 $98,999 $3,000 $7,140 $109,139
19 58 $109,139 $3,000 $7,850 $119,989
20 59 $119,989 $3,000 $8,609 $131,598
21 60 $131,598 $3,000 $9,422 $144,020
22 61 $144,020 $3,000 $10,291 $157,311
23 62 $157,311 $3,000 $11,222 $171,533
24 63 $171,533 $3,000 $12,217 $186,750
25 64 $186,750 $3,000 $13,283 $203,033

At the end of year 25, Clara is 64 and the HSA balance is $203,033. Path A has $0. The difference is $203,033.

Notice that the growth in the final year is $13,283, which is larger than the $3,000 contribution. That is compounding doing its work. The account is no longer mostly contributions; it is mostly earnings.

What the tax deduction adds

The table above shows the balance inside the HSA. It does not show the tax savings from the deduction. If Clara is in the 22% federal bracket, each $3,000 contribution saves $660 in federal income tax. Over 25 years, that is $16,500 in nominal tax savings, assuming her bracket does not change. If she invests those savings in a taxable account, the combined result is larger still. I am leaving that out of the main comparison because it complicates the ledger and because the bracket assumption is personal. But it is real money, and it tilts the comparison further toward Path B.

There is a second tax advantage: the earnings inside the HSA are not taxed each year. In a taxable account, dividends and realized capital gains would be taxed annually or on sale. In the HSA, they are not taxed at all as long as distributions are for qualified medical expenses. Over 25 years, that tax drag is a meaningful difference. The exact size depends on the fund’s yield and turnover, which is why I am not putting a single number on it here.

What happens after 65

At 65, Clara enrolls in Medicare. Publication 969 says she can no longer contribute to an HSA once she is enrolled in Medicare, but she can still use the existing balance for qualified medical expenses, including Medicare premiums other than Medigap. She can also take distributions for non-medical expenses after 65 without the 20% additional tax, but those distributions are included in gross income. That is the same tax treatment as a traditional IRA, which is why some people call the HSA a stealth retirement account. The difference is that qualified medical expenses come out tax-free at any age.

If Clara has $203,033 at 65 and spends it on Medicare premiums and medical expenses over 20 years, the balance can cover a substantial portion of her health care costs. If she instead withdraws it for non-medical expenses, she pays ordinary income tax on the withdrawals, but no penalty. The arithmetic of the HSA is not just about the balance; it is about the order in which she uses it.

What could go wrong

The 7% return assumption is the biggest lever. If the return is 4% instead of 7%, the ending balance is roughly $130,000 instead of $203,033. If the return is 10%, it is roughly $350,000. The comparison between Path A and Path B does not change, because Path A is always $0. But the size of the gap does.

The second lever is the contribution amount. If Clara contributes the 2025 self-only limit of $4,300 instead of $3,000, the ending balance is larger. If she contributes the family limit of $8,550, it is larger still. The arithmetic scales.

The third lever is medical expenses. If Clara has a year with $10,000 of medical bills, she can withdraw from the HSA to pay them, which reduces the balance but also reduces her out-of-pocket cost. The HSA is not locked away from medical use; it is a dedicated medical account that happens to invest like a retirement account.

The fourth lever is recordkeeping. Publication 969 says you should keep records of your distributions and qualified medical expenses. If you are audited and cannot substantiate the expenses, the distribution may be taxable and subject to the 20% additional tax. This is not a reason to avoid the HSA; it is a reason to keep a folder.

The decision

If Clara pays the deductible from checking and funds the HSA, she ends up with $203,033 at 64 under the stated assumptions. If she pays the deductible from the HSA and never funds it, she ends up with $0. The difference is not a market prediction; it is the arithmetic of tax-free compounding on a fixed contribution.

The decision is not whether the HSA is a good idea in the abstract. It is whether Clara can pay current medical bills from cash flow and leave the HSA alone. If she can, the arithmetic is on her side. If she cannot, the HSA still works, but the balance is smaller because she is using it for its intended purpose. Either way, the account is not a gamble on future markets; it is a container for a tax advantage that either compounds or does not.

If you want to see how a smaller, more frequent contribution changes the same arithmetic, the article on what a ten-dollar weekly bump actually does to your retirement number walks through a similar ledger with a different contribution pattern. The mechanics are the same; the numbers are different.

Frequently asked questions

Can I pay my deductible from the HSA and still invest the rest? Yes. The HSA is a single account. You can withdraw for current medical expenses and leave the remainder invested. The arithmetic in this article assumes you do not withdraw, but the account does not force you to choose all or nothing.

What if I change jobs or health plans? Publication 969 says the HSA is portable. It stays with you if you change employers or leave the workforce. You can continue to use the balance for qualified medical expenses even if you are no longer eligible to contribute.

What happens if I enroll in Medicare? You can no longer contribute to the HSA once you are enrolled in Medicare, but you can use the existing balance for qualified medical expenses, including Medicare premiums other than Medigap. See Publication 969 for the details.

What if I use the HSA for non-medical expenses before 65? The distribution is included in gross income and subject to a 20% additional tax unless an exception applies. After 65, the 20% additional tax does not apply, but the distribution is still included in gross income.

Do I need to keep receipts? Yes. Publication 969 says you should keep records of your distributions and qualified medical expenses. The IRS can ask for them.

What are the 2025 contribution limits? For 2025, the self-only limit is $4,300 and the family limit is $8,550. These figures come from IRS Revenue Procedure 2024-25. The limits are adjusted annually for inflation.

Is the 7% return assumption realistic? It is an assumption, not a forecast. It is roughly the long-run nominal return of a diversified stock portfolio, but future returns will differ. The arithmetic is reproducible at any return assumption; the conclusion changes with the assumption.

Sources

Clara Roades writes about personal finance as arithmetic you can reproduce. This article is for illustration and does not constitute tax advice. Consult a qualified tax professional about your specific situation.