Picking a Health Plan? Do This Math Before You Look at the Deductible

Health Insurance · 6 min read · Updated October 29, 2026

A colleague of mine recently told me he'd enrolled himself and his wife in his employer's family plan. "It's cheaper than buying two plans," he said confidently.

I didn't argue — but I was pretty sure he was wrong. At our company, several employee-only plan options cost $0 in premiums. His family plan definitely did not. He'd never actually run the numbers; he just assumed "family plan" meant "family discount."

He's not alone. Every open enrollment, most people pick a health plan the same way: they glance at the deductible, pick the lowest one they can afford the premium for, and move on. It feels responsible. It's also the single most expensive mistake in open enrollment.

The only formula that matters

Forget the deductible for a minute. The number you're actually choosing is your total yearly cost:

Total cost = premiums you'll definitely pay + medical costs you might pay

Premiums come out of every paycheck whether you see a doctor or not. The deductible, copays, and coinsurance only kick in if you actually get care. A plan with a low deductible and a high premium can easily cost you more than a high-deductible plan — because the premium is guaranteed and the medical bills are not.

Here's a simplified example. Same employer, two plans, employee-only coverage:

	Plan A (low deductible)	Plan B (HDHP)
Monthly premium (your share)	$350	$110
Annual premiums	$4,200	$1,320
Deductible	$500	$3,500
Out-of-pocket max	$4,000	$6,000

Now run three scenarios:

Healthy year ($800 in care): Plan A costs $4,200 + $500 = $4,700. Plan B costs $1,320 + $800 = $2,120. Plan B wins by $2,580.
Medium year ($4,000 in care): Plan A costs $4,200 + about $1,500 = $5,700. Plan B costs $1,320 + $3,500 = $4,820. Plan B still wins.
Bad year ($30,000 in care): Plan A costs $4,200 + $4,000 (OOP max) = $8,200. Plan B costs $1,320 + $6,000 (OOP max) = $7,320. Plan B wins again.

The low-deductible plan only wins in a narrow middle band — and even there, rarely by much. The premium difference ($2,880 a year here) is money you pay no matter what. That's the deductible trap: you're prepaying for care you may never need.

Risk tolerance: the number that actually protects you

"But what if something catastrophic happens?" That's the right question — and the answer isn't the deductible either. It's the out-of-pocket maximum: the most the plan can make you pay in a year, premiums aside.

If worst-case protection is what lets you sleep at night, compare annual premiums + out-of-pocket max across plans. You'll often find the HDHP's worst case is lower than the PPO's worst case, because the premium savings outweigh the higher OOP max. Risk tolerance doesn't automatically mean "buy the low deductible." It means knowing your ceiling — and the ceiling is the OOP max, not the deductible.

A practical way to think about it:

You rarely get care and have cash reserves: the HDHP usually wins, and the tax perks below make it better still.
You have ongoing prescriptions or a planned surgery: price your actual expected care under each plan — the low-deductible plan can win here, but only if the math says so.
You want the lowest possible worst case: compare premiums + OOP max, not deductibles.

The HDHP's secret weapon: the HSA's triple tax break

If your employer offers a high-deductible plan paired with a Health Savings Account, the tax math deserves its own look. HSA dollars are:

Tax-deductible going in — contributions reduce your taxable income, and through payroll deduction they skip FICA tax too (something no 401(k) can do).
Tax-free growing — invest it and the growth is never taxed.
Tax-free coming out — for qualified medical expenses, at any age.

For 2027, you can contribute up to $4,500 (self-only) or $9,000 (family), plus $1,000 more if you're 55 or older. Many employers also seed your HSA with a few hundred dollars — free money that directly offsets the higher deductible. Unlike an FSA, the HSA is yours forever: it rolls over every year and goes with you if you change jobs.

Run the premium savings plus the tax savings, and the HDHP often beats the low-deductible plan by thousands — even in a medium-care year.

The spouse trap: "family plan" is not a family discount

Back to my colleague. Here's what he missed: employer plan pricing is rarely linear. Many employers heavily subsidize employee-only coverage — sometimes down to $0 — while the jump to family coverage is steep. Two separate enrollments can beat one family plan:

You take the free employee-only plan at your job.
Your spouse and kids go on an employee-plus-children tier — either at your job or your spouse's.

Before defaulting to the family plan, price all four combinations: everyone on Plan A, everyone on Plan B, and the two split versions. Our family plan chooser does exactly this math across low, medium, and high care scenarios, plus the worst case.

Two more spouse-related gotchas:

Spousal surcharges. Some employers add $100+/month if your spouse could get coverage at their own job but joins yours instead. That surcharge alone can flip the math.
Double coverage isn't double value. If both spouses have employer plans, covering each other usually means paying two premiums for overlapping coverage. One exception: a second plan can help if one of you expects very high costs — but again, run the numbers.

Your 10-minute open enrollment checklist

Write down each plan's annual premium (your share, from your paycheck).
Note the deductible and the out-of-pocket max.
Estimate your care for next year: low, medium, high — plus the worst case (premium + OOP max).
If there's an HDHP, add the HSA tax savings and any employer seed money.
If covering a spouse or kids, price the split enrollments, not just the family plan.
Check for a spousal surcharge before adding a spouse who has their own option.

Do this once, and you'll never pick a plan by deductible again.

Ready to run your own numbers? Try the Family Plan Chooser — plug in your plans' premiums, deductibles, and out-of-pocket maximums, and compare four coverage combinations across low, medium, and high care plus the worst case.

Educational only — not financial or tax advice. Plan details vary by employer; check your SPD and open enrollment materials.

Sources

IRS Revenue Procedure 2026-24: 2027 HSA contribution limits ($4,500 self-only / $9,000 family; $1,000 catch-up at 55+), HDHP minimum deductibles ($1,750 / $3,500) and out-of-pocket maximums ($8,700 / $17,400).
Plan comparison scenarios in this article use simplified illustrative numbers; your employer's premiums, deductibles, and OOP maximums will differ.