Wire Size for 200 Amp Circuit at 300 Feet
Official National Electrical Code (NEC) sizing recommendation for a 200 Amp breaker over a 300-foot one-way conduit run on a 240V supply circuit.
Full Installation & Conduit Specifications
Interactive CalculatorVoltage Drop Alert: Base 3/0 AWG Wire Exceeds 3% (3.83%)
NEC Section 210.19(A) Informational Note 4 recommends that feeder and branch circuits maintain voltage drop under 3% (and 5% total) to protect appliances from motor burnout and voltage sagging. Using upsized 250 kcmil copper wire successfully brings voltage drop back under safe limits.
Frequently Asked Technical Questions
What size copper wire is required for a 200 amp breaker at 300 feet?
Due to voltage drop over 300 feet (3.83% on base wire), the National Electrical Code (NEC) recommends upsizing copper wire from 3/0 AWG to 250 kcmil. This keeps the voltage drop under 3%, protecting your equipment from overheating and brownout damage.
Can I use aluminum wire for 200 amps at 300 feet?
Yes, you can use aluminum or copper-clad aluminum wiring. For 200A at 300ft, you will need 250 kcmil aluminum conductors with terminals rated AL7CU or AL9CU and anti-oxidant paste where required.
What is the maximum continuous load permitted on a 200 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 200A breaker, your maximum continuous draw is 160.0 Amps.
What size conduit is recommended for this 300 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 2" or 2-1/2" EMT / Schedule 80 PVC.