The short answer
The biggest difference between an HMO and a PPO is how much freedom you have to see doctors outside the plan's network. HealthCare.gov explains that an HMO usually limits coverage to doctors who work for or contract with the HMO, while a PPO lets you see doctors outside the network without a referral for an added cost. If you mostly want lower hassle and stick with local doctors, an HMO can fit. If you want room to see specialists or out-of-network doctors, a PPO gives you more of it. HealthCare.gov lays out all four common types on its health plan and network types page.
What a network is
Every plan has a network. That's the group of doctors, hospitals and other providers the insurance company has a contract with. When you stay in that group, you usually pay less. When you step outside it, the plan type decides what happens next.
That is really the whole story behind the letters. HMO, PPO, EPO and POS are just different rules for how your plan treats the network.
How an HMO works
HMO stands for Health Maintenance Organization. HealthCare.gov says it usually covers care only from doctors who work for or contract with the HMO. It generally won't cover out-of-network care except in an emergency.
HMOs often focus on prevention and wellness. Many have you pick a primary care doctor who helps coordinate your care. If your doctors are already in the network, that setup can feel simple.
How a PPO works
PPO stands for Preferred Provider Organization. You pay less when you use doctors in the plan's network. You can still see doctors outside it, and you don't need a referral to do it. You'll just pay more when you go out of network.
That extra freedom is the main reason people choose a PPO. It can matter a lot if you travel for work or already see a specialist you love.
The two other types you'll see
When you shop, you'll also run into EPOs and POS plans.
An EPO, or Exclusive Provider Organization, only covers care from doctors and hospitals in its network, except in an emergency. In that way it acts a lot like an HMO.
A POS, or Point of Service plan, is a mix. You pay less in network, but HealthCare.gov notes that POS plans require a referral from your primary care doctor to see a specialist.
How I'd think about it if you work for yourself
When you're self-employed, nobody at an HR desk picks your plan for you. So I start with your doctors. Make a short list of the doctors and specialists you want to keep, plus your regular prescriptions. Then check each plan's provider directory before you decide.
For families, I'd also look at where your kids already go for care. A plan type is only as good as the network behind it in your area.
Cost matters too, and plan types can differ there. I won't guess at numbers here because they change by plan and by area. On a call we can look at the real options side by side.
If you're comparing plans for next year, my post on Marketplace Open Enrollment dates for self-employed people has the deadlines. And if you already have a plan, read what to do with your 2027 renewal letters before you let it roll over.
FAQ
What is the main difference between an HMO and a PPO?
It comes down to the network. HealthCare.gov says an HMO usually limits coverage to doctors who work for or contract with the HMO. A PPO lets you see out-of-network doctors without a referral, for an added cost.
Do I need a referral to see a specialist?
It depends on the plan type. PPOs don't require one. HealthCare.gov says POS plans require a referral from your primary care doctor to see a specialist. Many HMOs work through a primary care doctor too, so check the plan details.
Does an HMO cover emergencies out of network?
HMOs generally don't cover out-of-network care except in an emergency. Read your plan's documents for exactly how it handles emergency care.
What is an EPO?
An EPO is an Exclusive Provider Organization. HealthCare.gov says it covers services only when you use doctors, specialists or hospitals in the plan's network, except in an emergency.
How do I know if my doctor is in a plan's network?
Look up your doctor in the plan's provider directory before you enroll. You can also call the doctor's office and ask which plans they take.