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Wire size for 250 amps at 125 feet

250 A at 125 ft one-way

Voltage	Conductor	Minimum size	Voltage drop
120 V	Copper	250 kcmil	3.22 V (2.68%)
120 V	Aluminum	400 kcmil	3.31 V (2.76%)
240 V	Copper	250 kcmil	3.22 V (1.34%)
240 V	Aluminum	350 kcmil	3.78 V (1.58%)

Smallest size meeting NEC 75 °C ampacity (with 240.4(D) limits) and ≤3% drop at the full 250 A. Use 125% sizing for continuous loads; apply derating for more than 3 current-carrying conductors or high ambient temperature.

Adjust the numbers

Load current (amps)

One-way length (feet)

Voltage

Conductor

Max voltage drop (%)

Continuous load?

FAQ

What size wire for 250 amps at 125 feet?

At 240 V: 250 kcmil copper keeps voltage drop under 3%. See the table for 120 V and aluminum.

Same current, other distances

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