Wire Size for 70 Amp Circuit at 150 Feet
Official National Electrical Code (NEC) sizing recommendation for a 70 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 (2.7%)
At 150 feet under a 70A load, standard #4 AWG copper conductors experience only a 2.7% voltage reduction. No wire gauge upsizing is required.
Frequently Asked Technical Questions
What size copper wire is required for a 70 amp breaker at 150 feet?
For a 70 amp circuit at 150 feet on a 240V system, standard #4 AWG copper wire is sufficient. The calculated voltage drop is only 2.7%, well within the NEC recommended 3% limit.
Can I use aluminum wire for 70 amps at 150 feet?
Yes, you can use aluminum or copper-clad aluminum wiring. For 70A at 150ft, you will need #2 AWG aluminum conductors with terminals rated AL7CU or AL9CU and anti-oxidant paste where required.
What is the maximum continuous load permitted on a 70 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 70A breaker, your maximum continuous draw is 56.0 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" EMT or Schedule 40 PVC.