The four numbers that determine your real health insurance cost
Comparing health plans by monthly premium alone is the single most common — and most expensive — mistake Americans make. A plan with $100 lower monthly premiums can cost you $3,000 more in a year if you actually use medical care. The four numbers that matter are premium, deductible, coinsurance, and out-of-pocket maximum.
How the math works
You pay the full negotiated rate for care until you've spent your deductible. Then insurance kicks in coinsurance — typically 80/20 or 70/30 — meaning you pay 20% or 30% of every bill. Once your out-of-pocket spending hits the OOP max, insurance covers 100% for the rest of the year.
Rules of thumb
- Low expected medical use (healthy, no planned procedures): high-deductible plan with HSA — premiums are low and you get tax-advantaged savings.
- High expected medical use (chronic condition, planned surgery, pregnancy): lower deductible plan — the higher premium pays for itself quickly.
- Always check whether your doctors and medications are in-network before enrolling.
HSAs (Health Savings Accounts) are the only triple-tax-advantaged account in the US tax code: contributions are deductible, growth is tax-free, and withdrawals for qualified medical expenses are tax-free. If you can afford a high-deductible plan, max out the HSA.
Frequently asked questions
What is a high-deductible health plan (HDHP)?
A plan with a higher deductible (minimum $1,650 individual / $3,300 family in 2025) but lower premiums. HDHPs can be paired with a Health Savings Account (HSA) — the only triple-tax-advantaged account in the US tax code. Good for healthy people who don't expect major medical use.
Should I choose HMO, PPO, or EPO?
HMO: lowest cost, requires PCP referrals, no out-of-network coverage. PPO: highest cost, no referrals, out-of-network covered (at higher cost). EPO: middle ground, no referrals, but no out-of-network coverage (except emergencies). Most people prefer PPO for flexibility.
What is coinsurance vs copay?
Copay is a flat fee ($25 for a doctor visit). Coinsurance is a percentage (you pay 20%, insurance pays 80%) that applies AFTER you've met your deductible. Most plans mix both: copays for routine visits, coinsurance for major services.
What is the out-of-pocket maximum?
The most you can pay in a year for covered in-network care, including deductible, copays, and coinsurance. Once you hit this amount, insurance pays 100% for the rest of the year. For 2025, the ACA caps OOP max at $9,200 individual / $18,400 family.
Should I contribute to an HSA or FSA?
HSA (Health Savings Account): only available with HDHP, contribution limit $4,300 individual / $8,550 family in 2025, rolls over year-to-year, portable. FSA (Flexible Spending Account): use-it-or-lose-it each year, but available with any plan. Always max the HSA first if eligible.
Can I stay on my parents' plan until age 26?
Yes. The ACA allows you to remain on a parent's health insurance plan until your 26th birthday, regardless of marital status, financial dependence, or student status. This applies to all plans — employer-sponsored, marketplace, and individual.
What is the difference between in-network and out-of-network?
In-network providers have negotiated lower rates with your insurer. Out-of-network providers haven't, so you pay more (or all of the bill). For PPOs, out-of-network is covered at higher cost-sharing. For HMOs and EPOs, out-of-network is not covered at all (except emergencies).
Glossary of key terms
- Premium
- The monthly amount you pay for insurance coverage, regardless of whether you use medical services.
- Deductible
- The amount you pay out-of-pocket each year before insurance starts covering most costs. Higher deductible = lower premium.
- Coinsurance
- The percentage of costs you pay after meeting your deductible. Common splits: 80/20 or 70/30 (insurer/you).
- Out-of-Pocket Maximum
- The most you can pay in a year for covered in-network care. ACA caps at $9,200 individual in 2025.
- HSA (Health Savings Account)
- Tax-advantaged savings account for medical expenses, available only with HDHPs. Triple tax advantage: deductible contributions, tax-free growth, tax-free withdrawals for medical expenses.
Common mistakes to avoid
- Choosing a plan based on monthly premium alone — high-deductible plans can cost $3,000+ more per year if you actually use care
- Not checking whether your doctors and medications are in-network before enrolling
- Skipping the HSA when eligible — it's the only triple-tax-advantaged account in the tax code
- Using the emergency room for non-emergencies — ER visits cost 5-10× more than urgent care
- Not knowing your plan's out-of-pocket maximum before a major medical event
Pro tips
- If you're healthy and don't expect major medical use, choose an HDHP with HSA — invest the premium savings and HSA contributions for tax-free growth.
- If you have a chronic condition or planned surgery, choose a lower-deductible plan — the higher premium pays for itself quickly.
- Max out your HSA every year — even if you don't need it now, you can withdraw for past medical expenses tax-free in retirement.
- Always check if a generic alternative exists for your prescriptions — often 80-90% cheaper than brand name.
- Use GoodRx or similar discount cards if paying cash for prescriptions — sometimes cheaper than insurance copay.
Results are estimates for educational purposes only and not financial advice. Consult a licensed professional for advice specific to your situation.