Health plan selection is a decision under uncertainty dressed up as a shopping exercise. The premium is the only certain number; everything else depends on a year you have not lived yet. The way through is to stop asking "which plan is cheapest?" and start asking "which plan is cheapest across the range of years I might plausibly have?"
The four numbers that define a plan
| Term | What it means | Who pays |
|---|---|---|
| Premium | Fixed monthly cost of holding the plan | You, always |
| Deductible | Spend before most coverage begins | You, 100% |
| Coinsurance | Your share after the deductible, often 20% | Split |
| Copay | Flat fee per visit; may apply before deductible | You |
| Out-of-pocket maximum | Annual ceiling on in-network cost sharing | Insurer beyond it |
One nuance that trips people up: premiums do not count toward the out-of-pocket maximum. Your true worst case is twelve months of premiums plus the maximum.
Compare two plans properly
Find the crossoverEvery pair of plans has a spend level where the ranking reverses. Knowing that number tells you what you are actually betting on — and whether the bet is close.
The HSA argument for high-deductible plans
A qualifying high-deductible plan unlocks the health savings account: contributions reduce taxable income, growth is untaxed, and qualified withdrawals are untaxed. Payroll contributions also avoid Social Security and Medicare tax — an extra 7.65% that no other account offers.
The strategy that maximises this: pay routine medical costs from ordinary cash flow, invest the HSA balance for the long term, and archive every qualifying receipt. There is no time limit on reimbursement, so those receipts become permission slips for tax-free withdrawals decades later.
The conditionThis only works if you can absorb the deductible from cash without borrowing. A high-deductible plan paired with a thin emergency fund converts a manageable medical event into credit-card debt. Fund the buffer first.
Networks: the risk hiding behind the percentages
Coinsurance and out-of-pocket maximums apply to in-network care. Out-of-network treatment can be subject to a separate, much higher maximum — or none at all. The most common way a well-insured household ends up with a five-figure bill is an out-of-network provider inside an in-network facility.
- Verify your specific physicians on the insurer's directory, then confirm by phone with the practice.
- For any planned procedure, ask in writing whether anaesthesia, pathology, radiology and assistants are in network.
- Check the hospital tier — some plans place major systems in a costlier tier without leaving the network.
- Confirm your prescriptions appear on the formulary at a tier you can afford; a single specialty drug can dominate the comparison.
Reading the summary of benefits without falling asleep
- Out-of-pocket maximum, individual and familyYour worst case. Write it down first.
- Deductible structureEmbedded means one person's spending can trigger their own coverage; aggregate means the whole family deductible must be met first. This matters enormously for families.
- What is covered before the deductibleMany plans cover preventive care, primary visits and generics from day one. This can be worth more than a lower deductible.
- Prescription tiersFind your medications on the formulary and check both tier and prior-authorisation requirements.
- Referral requirementsGatekeeper designs are cheaper but slower. If you use specialists routinely, factor in the friction.
Limits, errors and borders of the standard advice
Critical reviewPlan-selection advice is shaped by employers wanting cost control and by financial writers who like the tax arithmetic of high-deductible plans. Both under-weight what happens to someone who actually gets ill.
"Choose the high-deductible plan — the premium saving plus the tax account wins."
The claimLower premiums and a tax-advantaged savings account make high-deductible plans mathematically superior.
Where it breaksThe arithmetic works for a healthy household with enough cash to absorb the deductible and enough income for the tax shelter to matter. It fails for people with chronic conditions, a family with regular care, anyone planning a pregnancy, or a household without liquid savings — for whom the deductible is not a theoretical maximum but a near-certain annual cost, often arriving before the savings account has anything in it. There is also a documented behavioural effect: higher cost-sharing reduces necessary care as well as unnecessary care, which can raise total cost later. The advice is popular partly because it aligns with employers shifting cost to employees.
The borderHigh-deductible plans suit healthy, higher-income households with a funded buffer who will genuinely invest the account. Low-deductible plans suit predictable ongoing care, tight cash flow, or anyone for whom hitting the deductible is likely rather than possible.
"Compare plans by adding premium plus deductible."
The claimTotal annual premium plus the deductible gives a comparable worst-case figure.
Where it breaksIt omits the number that actually bounds your exposure — the out-of-pocket maximum, which sits above the deductible and includes coinsurance after it. It also ignores coinsurance rates, separate prescription deductibles, per-service copays that may not count toward the deductible, and network structure. Two plans with identical premium-plus-deductible figures can differ by a large amount in a bad year. And it ignores the single biggest determinant of a large bill in some systems: whether the providers you would actually use are in network.
The borderModel three scenarios — a healthy year, a typical year with your known prescriptions and visits, and a bad year hitting the out-of-pocket maximum. Compare all three across plans, and check your own doctors and hospitals against each network before anything else.
"Never leave money in an FSA — it's use-it-or-lose-it."
The claimForfeiture risk means flexible spending accounts should be funded minimally.
Where it breaksThe forfeiture rule is often less absolute than the slogan — grace periods and limited carryover provisions exist in many plans, and the tax saving on funded amounts is immediate and certain while the forfeiture risk applies only to the unspent remainder. Underfunding to avoid forfeiture routinely costs more in foregone tax relief than the small amount at risk. The advice also causes year-end spending on unnecessary items, which is forfeiture by another route. Conversely, over-funding on the assumption of carryover fails when the specific plan has none.
The borderFund to your reliably predictable annual spending — recurring prescriptions, planned dental and optical, known therapies — and check your specific plan's carryover or grace terms rather than assuming either extreme.
"Stay in network and you won't get surprise bills."
The claimChoosing an in-network facility protects you from unexpected charges.
Where it breaksFacility network status and practitioner network status are separate. An in-network hospital can staff your procedure with out-of-network anaesthetists, radiologists or pathologists, and emergency care gives you no opportunity to check anything. Laboratory and imaging work is frequently sent to a third party you never chose. Protections against some of these practices have been strengthened in various jurisdictions and are partial, condition-dependent and widely misunderstood. Verifying status by phone also produces answers that are not binding.
The borderNetwork discipline substantially reduces exposure and does not eliminate it. For planned procedures, get written confirmation of network status for the facility and each practitioner, and ask where labs and imaging are sent. Know your local surprise-billing protections before you need them.
This article describes a system of private plan selection that simply does not exist in many countries, where the whole decision is moot — readers there should treat it as inapplicable rather than translatable. We give no figures for deductibles, maximums or contribution limits, so the scenario modelling we recommend needs your own plan documents. And our emphasis on worst-case modelling is a risk preference: for a genuinely healthy household on a tight budget, the cheaper plan is often the right answer and our caution costs them premium they cannot spare.
Frequently asked questions
Is a lower deductible always safer?
No. You pay for the lower deductible through higher premiums every month whether you use care or not. If the annual premium difference exceeds the deductible difference, the richer plan cannot win under any usage scenario.
What happens to my HSA if I change plans?
The balance is yours permanently and can still be spent tax-free on qualified expenses. You simply cannot make new contributions in years you lack a qualifying high-deductible plan.
Do copays count toward the deductible?
Often not, though they usually count toward the out-of-pocket maximum. The plan document is authoritative — this varies by insurer and by service type.
How should I handle a surprise bill?
Request an itemised bill and compare it to the explanation of benefits. Billing errors are common. Ask about financial assistance policies and payment plans before paying with a credit card — hospital plans are frequently interest-free.
The bottom line
Build a three-scenario model — quiet, expected and bad year — and compare total annual cost including premiums. Check that your providers and prescriptions are genuinely covered. If cash flow allows the deductible, a high-deductible plan plus a fully funded, invested HSA is one of the strongest financial structures available. If it does not, buy the richer plan and treat the extra premium as the price of sleep.
Revision log. Jul 2026: added the two-plan comparison model and network verification checklist. Reviewed annually before open enrolment.