What Size Wire for a 125 Amp Circuit Breaker? (NEC Table 310.16)
Complete Copper vs. Aluminum AWG wire size, continuous load limit (100A max), ground wire gauge, and conduit sizing for 125A circuits (125A subpanels, solar backfeed breakers & light commercial feeders).
Direct NEC Table 310.16 Answer for 125 Amps
Common Applications for a 125A Circuit
125A subpanels, solar backfeed breakers & light commercial feeders. Remember that under the NEC 125% continuous-load rule (NEC 210.19 & 210.20), a standard 125A breaker can only supply up to 100A of continuous load (any load that runs for 3 hours or more without stopping, such as an EV charger or commercial lighting).
When to Upsize for Voltage Drop (Over 100 Feet)
If your one-way wire run exceeds 100 feet at 240V (or 50 feet at 120V), step up one wire gauge from 1 AWG to keep total line voltage drop under the NEC 3% branch-circuit recommendation. Use our Voltage Drop Calculator to check your exact footage.