Breaker sizing (the 125% rule)
EV charging is a continuous load, so the US electrical code requires the circuit breaker to be rated at least 125% of the charger’s output current: a 40 A charger needs a 50 A breaker, a 48 A charger a 60 A breaker.
Common pairings: 16 A → 20 A breaker, 32 A → 40 A, 40 A → 50 A, 48 A → 60 A, 80 A → 100 A. Most chargers with adjustable amperage can be set lower to fit an existing circuit.
Panel capacity is the usual constraint for 48 A+ installs — an electrician’s load calculation, or a charger with dynamic load management, solves it.