Wire Sizing

Wire Size for 100 Amp Sub-Panel 200 Feet

Pre-calculated NEC-compliant wire size for 100 amps at 200 feet on a 240V single-phase circuit. Immediate answer below.

Recommended Wire Size

Copper

1 AWG

Voltage drop: 2.57% (6.16V)

Voltage at load: 233.8V

Controlling factor: Voltage Drop (3% limit)

Aluminum

2/0 AWG

Voltage drop: 2.65% (6.36V)

Voltage at load: 233.6V

Controlling factor: Voltage Drop (3% limit)

Based on NEC Table 310.16 (75°C column), single-phase, 240V, 3% max voltage drop, one-way distance 200 ft.

Wire Comparison Table

Wire Size	Ampacity	V-Drop (V)	V-Drop (%)	V at Load
14 AWG	15A	125.6V	52.33%	114.4V
12 AWG	20A	79.2V	33%	160.8V
10 AWG	30A	49.6V	20.67%	190.4V
8 AWG	50A	31.12V	12.97%	208.9V
6 AWG	65A	19.64V	8.18%	220.4V
4 AWG	85A	12.32V	5.13%	227.7V
3 AWG	100A	9.8V	4.08%	230.2V
2 AWG	115A	7.76V	3.23%	232.2V
1 AWGREC	130A	6.16V	2.57%	233.8V
1/0 AWG	150A	4.88V	2.03%	235.1V
2/0 AWG	175A	3.87V	1.61%	236.1V
3/0 AWG	200A	3.06V	1.28%	236.9V
4/0 AWG	230A	2.43V	1.01%	237.6V
250 kcmil	255A	2.06V	0.86%	237.9V
300 kcmil	285A	1.72V	0.72%	238.3V
350 kcmil	310A	1.47V	0.61%	238.5V
400 kcmil	335A	1.28V	0.53%	238.7V
500 kcmil	380A	1.03V	0.43%	239V

Table shows all standard AWG/kcmil sizes for 100A at 200 ft on 240V (copper). Green check = meets both ampacity and 3% voltage drop. REC = smallest compliant size.

Key Considerations

Sub-panel feeders are subject to NEC 215.2(A)(1) which requires conductors to have ampacity not less than the rating of the overcurrent device. For a 100A sub-panel at 200 feet, voltage drop on the feeder is the primary sizing concern.

Remember that the total voltage drop from the service entrance to the farthest outlet should not exceed 5%. If the feeder uses 2-3%, branch circuits in the sub-panel should keep their drop to 2% or less.

For runs exceeding 200 feet, conduit fill becomes important. Verify that the selected wire size fits within the maximum fill allowance of your conduit per NEC Chapter 9, Table 1. Consider upsizing the conduit rather than downsizing the conductor.

Frequently Asked Questions

What size wire do I need for a sub-panel feeder at 200 feet?▾

For a 100A/240V circuit at 200 feet, use 1 AWG copper (2.57% drop) or 2/0 AWG aluminum. This keeps voltage drop within the NEC-recommended 3% limit.

Can I use aluminum wire for a 100 amp circuit?▾

Yes. Aluminum wire is a cost-effective alternative for larger circuits. For 100A at 200 feet, use 2/0 AWG aluminum (2.65% 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 100A circuit at 200 feet on 240V, exceeding 3% means the load receives less than 232.8V, which can damage sensitive electronics and shorten appliance lifespan.

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Need a Custom Calculation?

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

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