Wire Sizing

What Size Wire for 125 Amp 150 Feet Away

Pre-calculated NEC-compliant wire size for 125 amps at 150 feet on a 240V single-phase circuit. Immediate answer below.

Recommended Wire Size

Copper

1 AWG

Voltage drop: 2.41% (5.78V)

Voltage at load: 234.2V

Controlling factor: Ampacity (NEC 310.16)

Aluminum

2/0 AWG

Voltage drop: 2.48% (5.96V)

Voltage at load: 234V

Controlling factor: Ampacity (NEC 310.16)

Based on NEC Table 310.16 (75°C column), single-phase, 240V, 3% max voltage drop, one-way distance 150 ft.

Wire Comparison Table

Wire Size	Ampacity	V-Drop (V)	V-Drop (%)	V at Load
14 AWG	15A	117.75V	49.06%	122.3V
12 AWG	20A	74.25V	30.94%	165.8V
10 AWG	30A	46.5V	19.38%	193.5V
8 AWG	50A	29.18V	12.16%	210.8V
6 AWG	65A	18.41V	7.67%	221.6V
4 AWG	85A	11.55V	4.81%	228.5V
3 AWG	100A	9.19V	3.83%	230.8V
2 AWG	115A	7.28V	3.03%	232.7V
1 AWGREC	130A	5.78V	2.41%	234.2V
1/0 AWG	150A	4.58V	1.91%	235.4V
2/0 AWG	175A	3.63V	1.51%	236.4V
3/0 AWG	200A	2.87V	1.2%	237.1V
4/0 AWG	230A	2.28V	0.95%	237.7V
250 kcmil	255A	1.93V	0.8%	238.1V
300 kcmil	285A	1.61V	0.67%	238.4V
350 kcmil	310A	1.38V	0.57%	238.6V
400 kcmil	335A	1.2V	0.5%	238.8V
500 kcmil	380A	0.97V	0.4%	239V

Table shows all standard AWG/kcmil sizes for 125A at 150 ft on 240V (copper). Green check = meets both ampacity and 3% voltage drop. REC = smallest compliant size.

Key Considerations

For a 125A circuit at 150 feet on 240V, both ampacity and voltage drop must be satisfied. NEC recommends keeping the total voltage drop (feeder + branch) under 5%, with no more than 3% on either segment alone.

Copper conductors at 75°C column (THHN/THWN-2) are assumed. If using 60°C terminations, derate the ampacity to the 60°C column values. Verify the temperature rating of your terminals.

Frequently Asked Questions

What size wire do I need for a 125 amp service at 150 feet?▾

For a 125A/240V circuit at 150 feet, use 1 AWG copper (2.41% drop) or 2/0 AWG aluminum. This keeps voltage drop within the NEC-recommended 3% limit.

Can I use aluminum wire for a 125 amp circuit?▾

Yes. Aluminum wire is a cost-effective alternative for larger circuits. For 125A at 150 feet, use 2/0 AWG aluminum (2.48% voltage drop). Aluminum requires AL-rated connectors and anti-oxidant compound at all terminations.

What happens if the voltage drop exceeds 3%?▾

Voltage drop above 3% reduces equipment efficiency, can cause motors to overheat, and may violate NEC 210.19(A) Informational Note No. 4. For a 125A circuit at 150 feet on 240V, exceeding 3% means the load receives less than 232.8V, which can damage sensitive electronics and shorten appliance lifespan.

Related Wire Size Calculations

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100A / 150 ft

What Size Wire for 100 Amp 150 Feet Away

200A / 150 ft

What Size Wire for 200 Amp 150 Feet Away

Need a Custom Calculation?

Different voltage, three-phase, or custom max drop percentage? Use our interactive calculator.

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