Generator inlet breaker and wire size
Find the breaker and conductor size for the cable run from a generator power inlet to the panel. Every step is shown so an electrician can check it. The inlet must connect to the panel through an interlock kit or transfer switch, never a double-ended cord.
Basis
2023 NEC. Breaker: 125% of generator rated current, rounded up to a standard size in 240.6(A). Conductor: Table 310.16 75 C column (terminations, 110.14(C)), corrected with Table 310.15(B)(1), and never smaller than the breaker rating, plus the small conductor limits of 240.4(D). Voltage drop uses Chapter 9 Table 8 resistance and a 3% target (a recommendation, not a mandate). The 125% figure is a conservative planning rule; the generator maker's instructions and 445.13, 702.4 and 705 may set different values for your install. Results round to the safe side. Stops at 200 A.
Next: electrician quote checker, generator safety, generator size.