Why Barista FIRE exists in the US
Leaving full-time work usually means leaving employer health coverage years before Medicare at 65. The premium — after any ACA marketplace subsidy — is often the largest new bill the strategy has to fund. Competitors model this because it is the reason the strategy exists. A Barista FIRE number that ignores healthcare is a number for a country this reader does not live in.
ACA premiums and subsidies
Marketplace plans are priced by age, location and metal tier. Subsidies are a function of household income relative to the federal poverty level. A part-time job that looks perfect on a spending spreadsheet can push income through a subsidy cliff and raise the net premium by more than the job pays. Enhanced subsidies tied to the American Rescue Plan / Inflation Reduction Act have been extended and debated on a short fuse — treat the current year's rule as dated, not permanent.
In the calculator
Enter the net annual premium you would actually pay, for the years between semi-retirement and Medicare. The Barista FIRE calculator capitalises that stream at the withdrawal rate and adds it to the spending-gap number. Change the premium; the Barista FIRE number moves. That is the whole point of the field.
Employer part-time coverage, a spouse's plan, or an early-retiree HRA changes the net premium. Put the number you would write a cheque for, not a national average.