Medicare Part B 20% Coinsurance vs Medigap Plan G vs Medicare Advantage Copay: What the Same Outpatient Procedure Costs at a Hospital vs a Surgery Center in 2026

You get your Annual Notice of Change letters in the next few days. Open enrollment opens October 15 and closes December 7. Before you decide whether to keep your plan, answer one question: what would you pay for a knee scope, a cataract surgery, or a colonoscopy with polyp removal at the facility your surgeon actually uses?

Most people compare premiums. The plan that costs less per month is often not the plan that costs less when you have a procedure. The facility, the deductible you have already met, and the plan type together decide the bill. The sections below show how, with numbers you can rerun for your own situation.

Why the cost of care is the story right now

Several recent stories point the same way, even though they cover different topics.

Cost of care is a pocketbook issue. A new KFF-AP poll reported by KFF Health News found rural voters ranking the cost of living and the cost of healthcare among the top issues they want candidates to address. Many rural beneficiaries also have fewer facilities to choose from, so price shopping is harder for them.
Billing may get more expensive before it gets cheaper. In the Healthcare Dive report "AI will inflate healthcare costs before lowering them, Oz says," CMS Administrator Mehmet Oz said AI could "turbocharge" medical billing and raise costs in the near term. A separate Healthcare Dive piece, "Health execs want strong returns on IT investments," notes that revenue cycle tools are drawing attention. Those tools are built to help providers bill more completely. Your itemized statement is worth reading closely.
Coverage eligibility is changing for some people. Medicare Rights Center reported this week that thousands of immigrants are scheduled to lose Medicare coverage in the new year under H.R. 1. Medicare Rights has commented on the proposed CMS rule that implements the change. If you or someone you help is affected, the cost comparison below changes, because losing Part B means paying full price or moving to other coverage. We covered that in Medicare Part D's $2,000 Drug Cap vs ACA Marketplace Costs.

The UnitedHealth report about a new chief administrative officer is a corporate personnel item. It does not change what you pay.

The 2026 numbers you need before comparing

These are the standard 2026 figures. Confirm them against your own plan documents.

Item	2026 amount
Part B standard premium	$202.90/month
Part B deductible	$283
Part B coinsurance after deductible	20%, no annual cap
Part A inpatient deductible (per benefit period)	$1,736
Medicare Advantage in-network out-of-pocket maximum (limit)	$9,250
Part D out-of-pocket cap	$2,100

The line that matters most for procedure costs is the last row of the Part B section. Original Medicare alone has no cap on the 20%. That is why Medigap Plan G exists.

Worked example: same knee arthroscopy, two locations, three plan types

Assume the Medicare-approved amount for a knee arthroscopy is $2,400 at an ambulatory surgery center (ASC) and $4,300 at a hospital outpatient department. Medicare pays hospital outpatient departments more than ASCs for many of the same procedures, and the 20% is calculated on that higher number. These figures are illustrative. Your actual approved amounts vary by procedure and region, so treat them as a template.

Original Medicare only (no Medigap), deductible not yet met:

ASC: $283 + 20% × ($2,400 − $283) = $283 + $423.40 = $706.40
Hospital: $283 + 20% × ($4,300 − $283) = $283 + $803.40 = $1,086.40

Original Medicare + Medigap Plan G: Plan G pays the 20% coinsurance and does not cover the Part B deductible.

ASC: $283
Hospital: $283

The facility price difference disappears from your bill, but you pay for that protection in the premium.

Medicare Advantage (example plan): Assume a $150 copay at an ASC and a $350 copay at a hospital outpatient department. Plans set these amounts themselves, so yours may differ.

ASC: $150
Hospital: $350

Scenario	ASC	Hospital outpatient
Original Medicare only	$706.40	$1,086.40
Original Medicare + Plan G	$283	$283
Medicare Advantage (example copays)	$150	$350

On a single procedure, the Medicare Advantage plan looks cheapest. That is the trap. The Medicare Advantage figure assumes the surgery center and surgeon are in your network, that prior authorization is approved, and that this is your only claim of the year. Change any of those assumptions and the result changes. Every plan comparison should be run against your own facilities, not against a generic price.

This is the kind of analysis Toravine runs for you. It lets you compare plans against the facilities and procedures you might actually use, without building the spreadsheet yourself.

The 10-year premium math behind the comparison

A $0 premium is not a free plan. Here is a simple 10-year model.

Medigap Plan G: Assume $170/month at age 65, rising 6% a year. That growth rate is an assumption; Plan G premiums have risen faster in some years and slower in others.

Annual premium in year 1: $170 × 12 = $2,040. Ten-year total with 6% annual increases: $2,040 × (1.06¹⁰ − 1) / 0.06 = $2,040 × 13.18 = about $26,900. Add ten years of the Part B deductible ($283 at today's amount, more later) and you land near $29,700 in Plan G-related costs, before Part B and Part D premiums, which you pay under either path.

Medicare Advantage at $0 premium: Premium total is $0, but your exposure depends on use.

Light-use decade at about $600/year in copays: $6,000
Heavy-use decade at about $4,000/year: $40,000
Worst-case year: up to $9,250 in-network in a single year

Based on Toravine's analysis of 11,267 data points, the medigap_rates dataset (3,570 rows) shows Plan G quotes for a 65-year-old spanning a wide range by ZIP code and by rating method (community-rated, issue-age, attained-age). Attained-age quotes start lowest and rise fastest. Comparing only the year-one premium understates the ten-year cost of an attained-age policy. Our cms_medicare_plan_premiums dataset (1,236 rows) shows the mirror image on the Medicare Advantage side: many plans advertise $0 premiums, and the difference shows up in copays, prior authorization rules, and network size.

For deeper 10-year models, see Medicare Advantage $0 Premium vs Medigap Plan G $160/Month: 10-Year Out-of-Pocket Cost Comparison and Medicare Advantage HMO vs Original Medicare + Medigap Plan G for Chronic Conditions.

IRMAA: the premium surcharge that can change the whole comparison

IRMAA is the income-related surcharge on Part B and Part D premiums. It is based on your tax return from two years earlier, so your 2026 premium reflects your 2024 income. Our cms_medicare_irmaa dataset (174 rows) captures the bracket structure.

The first 2026 threshold is $109,000 modified adjusted gross income for a single filer and $218,000 for a joint return.

Example: single filer, 2024 MAGI of $115,000

Standard Part B: $202.90/month
Part B with the first IRMAA tier: $284.10/month
Extra Part B: $81.20 × 12 = $974.40/year
Part D IRMAA add-on at the first tier: about $14.50/month, or $174/year
Total extra: about $1,148/year, or $11,480 over a decade if income stays in that bracket

This matters for the plan comparison for two reasons. First, IRMAA applies to you under either path. It is a cost that does not vary by plan type, so it will not change which plan is cheaper. It does change how much of your budget is committed before you use any care. Second, a one-time income event such as a Roth conversion, a home sale, or a large CD payout can push you over a threshold for a single year. If that event was a one-off, you can appeal with Form SSA-44 using a life-changing event. Retirement is a common qualifying event. See IRMAA and CD Interest in 2026 for how savings interest can push a $185 premium toward $259.

Where your local prices and your plan collide

Four personal variables decide your best option.

1. Deductible status

If you have already met your Part B deductible, the 20% starts immediately on Original Medicare only. Deductibles reset in January. A procedure scheduled in December can cost less to you than the same procedure in January.

2. Facility type

The ASC vs hospital outpatient department gap in the example above ($706 vs $1,086 on Original Medicare alone) is a $380 difference for one procedure. On larger procedures the gap can be well over $1,000. Ask the surgeon's office whether the procedure can be done at an ASC, and ask for the billing code so you can look up the approved amount.

3. Network and prior authorization

If you have Medicare Advantage, your surgeon and facility both need to be in network. An out-of-network claim on an HMO may not be covered at all. Prior authorization delays and denials are a real cost of Medicare Advantage. The Office of Inspector General's finding that most reviewed denials were overturned on appeal is covered in Medicare Advantage Part D Formulary Denials in 2026. Appeals cost time, and sometimes they cost care delayed.

4. Where you live

The census_acs_medicare dataset (6,287 rows) captures how beneficiary populations, income, and age distributions vary across areas. Rural areas often have fewer facilities and fewer plan choices, and your county's mix of ASCs, hospitals, and Medicare Advantage networks changes your options. If your county has one hospital system and no ASC within 40 miles, the facility comparison above may not apply, and network breadth becomes the more important question.

The irreversible decisions

Because you are approaching open enrollment, flag these before you switch.

Medigap underwriting. Outside your six-month Medigap open enrollment window (starting when you are 65 and enrolled in Part B), most states let insurers use medical underwriting for a new Medigap policy. If you move from Medicare Advantage back to Original Medicare later, you may be turned down or charged more for Plan G. A few states, including New York, Connecticut, Massachusetts, and Maine, have more permissive rules. Check your state.
Late enrollment penalties. The Part B penalty is 10% for each full 12-month period you could have had it and did not. It applies for life. The Part D penalty is 1% of the national base beneficiary premium for each month without creditable coverage, also for life.
Switching windows. From October 15 to December 7 you can change Medicare Advantage or Part D plans. From January 1 to March 31, Medicare Advantage enrollees have a one-time chance to switch plans or return to Original Medicare. Switching back to Original Medicare does not guarantee a Medigap policy. See Medicare Advantage Open Enrollment Ends March 31.

A price-check routine before you schedule anything

Get the procedure code (CPT) from your surgeon's office. Ask which facility they use and whether an ASC is an option.
Look up the Medicare-approved amount for that code at each facility using Medicare's Procedure Price Lookup tool.
Calculate your share using the plan formula: deductible first, then 20% of the remainder on Original Medicare only; $0 coinsurance with Plan G; or your plan's copay schedule for Medicare Advantage.
Check your plan's Annual Notice of Change for 2027 changes to copays, network, and prior authorization rules.
Ask for an itemized bill after the procedure and compare it to the Medicare Summary Notice. With billing tools getting more sophisticated, as the Healthcare Dive coverage above describes, reviewing the itemization is worth ten minutes.

Which option fits which person

Your situation	Likely better fit	Why
Expect several procedures or a chronic condition, want predictable costs	Plan G	No 20% exposure, no network restrictions
Healthy, tight budget, doctors are all in network	Medicare Advantage	Lower fixed cost, capped exposure
Income above the IRMAA threshold	Run both options	IRMAA is the same either way; the plan-type gap is what to compare
Rural, one hospital system	Check networks first	Network breadth may outweigh premium
Recently lost Medicare eligibility or coverage	Talk to a SHIP counselor	Options and deadlines differ

For free, personalized counseling, your State Health Insurance Assistance Program (SHIP) offers unbiased help, and the number is on Medicare.gov.

Run your own numbers before October 15

The point of this comparison is that there is no single right answer. A plan that costs $1,000 less in a healthy year can cost $6,000 more in a bad one. The Part B deductible, your facility choice, IRMAA, and your network each move the total. You can check it for your own situation by entering your plan, your doctors, and your likely procedures at Toravine. Do that before October 15, while you can still change plans, and before you schedule anything you can price-shop.

Data behind this post

The figures above are computed from the product's own reference tables, last refreshed 2026-09-20:

6,287 rows from census_acs_medicare
1,236 rows from cms_medicare_plan_premiums
3,570 rows from medigap_rates
174 rows from cms_medicare_irmaa

Sources

Economic Frustration Tests Trump’s Standing With Rural Voters, New KFF-AP Poll Finds — KFF Medicare
Thousands of Immigrants Scheduled to Lose Medicare Coverage in the New Year — Medicare Rights Center
Health execs want strong returns on IT investments — Healthcare Dive
AI will inflate healthcare costs before lowering them, Oz says — Healthcare Dive
UnitedHealth names first chief administrative officer — Healthcare Dive