Picking a Health Plan: The Deductible-vs-Premium Math Nobody Shows You

Open enrollment arrives, you're staring at two health plans, and the choice feels impossible. Plan A costs $150 a month with a $5,000 deductible. Plan B costs $350 a month with a $1,000 deductible. Your brain says Plan B is "better" — lower deductible sounds safer — but your wallet says Plan A saves you $2,400 a year in premiums. Which one is actually cheaper? Almost nobody does the math. Let's do it.

The total cost of a health plan is three numbers added together: what you pay in premiums all year, what you pay out of pocket when you actually use care, and then you stop paying once you hit the out-of-pocket maximum. The trick is that you can't know the middle number in advance, so you have to estimate it for three scenarios: a healthy year, a normal year, and a bad year.

Start with the healthy year. You go for a checkup and get a prescription. Preventive care is free under most plans, so your care costs are maybe $100 either way. Plan A costs you $1,800 in premiums plus $100 in care: $1,900 total. Plan B costs $4,200 in premiums plus $100 in care: $4,300 total. In a healthy year — which is most years for most young people — Plan A wins by $2,400. That's not a small difference; that's the whole premium gap, kept.

Now the normal year. You sprain an ankle, get an MRI, a few physical therapy visits. Total billed care: $3,000. Under Plan A, you pay the first $1,800 of premiums, then you pay the first $3,000 of care since it's all under the deductible. Total: $4,800. Under Plan B, you pay $4,200 in premiums, then your first $1,000 of care (the deductible), then the plan covers most of the rest — say coinsurance at 20%, so another $400. Total: roughly $5,600. Plan A still wins, by about $800. The expensive plan only starts pulling ahead when your care costs get big.

Now the bad year. You need surgery. Total billed care: $25,000. Plan A: $1,800 in premiums, then you pay the $5,000 deductible, then coinsurance until you hit the out-of-pocket maximum — let's say the max is $7,000, so your care cost caps at $7,000. Total: $8,800. Plan B: $4,200 in premiums, $1,000 deductible, coinsurance up to a $4,000 out-of-pocket max. Total: $8,200. In the catastrophic year, Plan B finally wins — by $600, after costing you $2,400 more in premiums all year.

So the pattern is clear: the cheap-premium plan wins in healthy and normal years, the expensive plan wins only in bad years, and even then by a modest margin. For most people most of the time, the low-premium, high-deductible plan is the better financial bet. The insurance company knows this, by the way — that's why the expensive plan exists. It's a worry-reduction product, not a money-saving product.

There are two wrinkles worth knowing. First, if your employer offers a Health Savings Account with the high-deductible plan, that changes everything — HSA contributions are pre-tax, the money grows tax-free, and withdrawals for medical expenses are tax-free. It's the single best tax deal available to regular people, and it only comes with high-deductible plans. Second, if you have a known condition — you're pregnant, you need ongoing treatment, you're scheduling a surgery — run the numbers with your actual expected care, because then the bad-year scenario is the likely one and the math flips.

One more thing: check the out-of-pocket maximum, not just the deductible. Two plans can have the same deductible but very different maximums, and the maximum is what protects you in the disaster year. A $5,000 deductible with a $7,000 max and a $5,000 deductible with a $9,000 max are not the same plan, even though the marketing makes them look similar.

The rule of thumb: if you're young, healthy, and rarely see a doctor, take the cheap plan and bank the premium difference — ideally into the HSA. If you know you're going to use a lot of care this year, take the expensive plan and make the system work for you. And either way, do the three-scenario math yourself. The enrollment brochure shows you the premiums in big type and the deductible in medium type and buries the out-of-pocket max in a footnote. Now you know which numbers actually decide the winner.

Disclosure: This article was drafted with AI assistance and reviewed by the author.