What size wire for 100 amps at 200 feet?
Short answer: For a 100 amp load 200 feet away (one way) at 240 V, use 1 AWG copper or 2/0 AWG aluminum in conduit with 75 °C terminations, which keeps voltage drop at 2.6% and 2.7%. In NM-B (Romex) cable it is 1 AWG copper. The breaker stays 100 A; the extra size is only for distance.
100 amps at 200 feet: wire size by type
| Wire type | Size by ampacity | Size for 200 ft (≤3% drop) | Voltage drop |
|---|---|---|---|
| Copper THHN/THWN-2 in conduit, 75 °C | 3 AWG | 1 AWG | 2.57% |
| Aluminum XHHW-2 in conduit, 75 °C | 1 AWG | 2/0 AWG | 2.65% |
| Copper NM-B (Romex) cable, 60 °C | 1 AWG | 1 AWG | 2.57% |
| Aluminum SER / NM-B cable, 60 °C | 1/0 AWG | 2/0 AWG | 2.65% |
That is one or more sizes above the 3 AWG that ampacity alone allows: at 200 ft the run, not the breaker, decides the gauge. NEC 250.122(B) then requires the equipment ground to be increased in proportion: start from 8 AWG copper for a 100 A breaker.
Voltage drop of each gauge over 200 ft
| Wire | Volts lost at 100 A | Drop at 100 A | Drop at 80 A (80%) |
|---|---|---|---|
| 3 AWG copper | 9.80 V | 4.08% | 3.27% |
| 2 AWG copper | 7.76 V | 3.23% | 2.59% |
| 1 AWG copper | 6.16 V | 2.57% | 2.05% |
| 1/0 AWG copper | 4.88 V | 2.03% | 1.63% |
| 2/0 AWG copper | 3.87 V | 1.61% | 1.29% |
voltage drop = 2 × length × resistance per 1,000 ft × amps ÷ 1,000
= 2 × 200 × R(1 AWG) × 100 ÷ 1,000 = 6.16 V
percent = 6.16 ÷ 240 × 100 = 2.57%
If the real load is the 80% continuous maximum (80 A, as with an EV charger on a 100 A breaker), copper in conduit can be 2 AWG. 3% is the NEC's recommendation for a branch circuit (Informational Note to 210.19), not a hard rule, but motors, compressors and chargers run better with it.
Same 100 A, other distances
50 ft · 75 ft · 100 ft · 150 ft. Minimum sizes with no distance correction: what size wire for a 100 amp breaker.
Other loads at 200 feet
30 A · 40 A · 50 A · 60 A · 125 A · 150 A · 200 A
Change the numbers in the calculator
Safety. A 100 A circuit or feeder over 200 ft needs a permit almost everywhere in the US. Buried runs have their own depth and conduit rules (NEC 300.5), and equipment nameplates override any general table.