Wire Size for 125 Amp Circuit at 150 Feet
Official National Electrical Code (NEC) sizing recommendation for a 125 Amp breaker over a 150-foot one-way conduit run on a 240V supply circuit.
Full Installation & Conduit Specifications
Interactive CalculatorCode Compliant: Voltage Drop is Within Safe Tolerance (2.41%)
At 150 feet under a 125A load, standard #1 AWG copper conductors experience only a 2.41% voltage reduction. No wire gauge upsizing is required.
Frequently Asked Technical Questions
What size copper wire is required for a 125 amp breaker at 150 feet?
For a 125 amp circuit at 150 feet on a 240V system, standard #1 AWG copper wire is sufficient. The calculated voltage drop is only 2.41%, well within the NEC recommended 3% limit.
Can I use aluminum wire for 125 amps at 150 feet?
Yes, you can use aluminum or copper-clad aluminum wiring. For 125A at 150ft, you will need 2/0 AWG aluminum conductors with terminals rated AL7CU or AL9CU and anti-oxidant paste where required.
What is the maximum continuous load permitted on a 125 amp breaker?
Per NEC Article 210.20, continuous loads (operating for 3 hours or longer, such as EV chargers or heaters) cannot exceed 80% of the breaker rating. For a 125A breaker, your maximum continuous draw is 100.0 Amps.
What size conduit is recommended for this 150 ft run?
Based on Chapter 9, Tables 1 and 4 of the NEC for up to 3-4 current-carrying conductors plus ground at a 40% maximum conduit fill, we recommend using 1-1/4" EMT or Schedule 40 PVC.