Subpanel Feeder (100A, 240V) Wire Gauge — NEC 2023 Sizing Guide
100A feeder for a garage or shop subpanel. Use 1 AWG aluminum. 100A at 75 ft on 240V: 1.58% voltage drop.
1 AWG
aluminum conductor
1.58%
voltage drop
100A
ampacity
Advanced options — derating, breaker & conduit
1 AWGaluminum
Ampacity OKVD 1.58%
1 AWG selected by ampacity (100A ≥ 100A).
Ampacity100Aat 75°C
Voltage drop1.58%3.8V
At load236.2Vreceiving end
Circular mils83,69042.4 mm²
Min for ampacity ← governs
1 AWG
83,690 CM
Min for ≤3% VD
3 AWG
52,620 CM
⚠Aluminum: use AL/CU-listed terminations and anti-oxidant compound.
Copper vs Aluminum (for 100A at 75 ft on 240V)
Copper
3 AWG
VD: 1.5% · 26.7 mm²
Aluminum
1 AWG
VD: 1.6% · 42.4 mm²
Subpanel Feeder (100A, 240V)
100A feeder for a garage or shop subpanel.
For a 100A load at 75 ft on 240V, use 1 AWG aluminum.
Garage workshop, ADU, or detached structure subpanel feeder
Required wire gauge
Ampacity governs
1 AWG aluminum
100A ampacity | 1.58% voltage drop | 240V system
Circuit specifications
NEC 2023 compliant. Min wire for ampacity: 1 AWG. Min wire for 2% VD: 2 AWG.
Preset distance sensitivity
How Subpanel Feeder (100A, 240V) sizing changes as one-way run distance changes.
Preset voltage drop by distance
Visual Analysis1 series6 points
Interactive line view for 1 series and 6 sampled points, built for quick reading and clear comparison.
Trend
Upward
Min
0.53
Max
1.99
Insight
Preset voltage drop by distance shows an upward pattern, with a visible peak around 150 ft at 1.99.X-axis: One-way distanceY-axis: Voltage drop (%)
Preset voltage drop by distance
Installation planning checklist
Checklist values are generated from the preset and must be confirmed against the actual equipment and local code before installation.
Copper vs aluminum preset alternatives
Preset alternatives keep the same load, voltage, distance, and voltage-drop target while changing conductor material.
Preset assumptions
This preset models 100A, 240V single-phase, 75 ft one-way, aluminum conductor, 75C temperature rating, and 2% maximum voltage drop.
Presets are planning shortcuts for common search intents. The equipment nameplate, MCA/MOCP values, continuous-load status, conductor count, ambient temperature, and local amendments can change the final answer.
Common use: Garage workshop, ADU, or detached structure subpanel feeder
Safety and code review notes
Confirm breaker size, conductor insulation, terminal temperature rating, grounding conductor, raceway fill, GFCI/AFCI rules, and wet-location requirements before installation.
For EV chargers, HVAC equipment, motors, spas, detached structures, and service feeders, nameplate and local-code rules can override a generic ampacity calculation.
This preset has warnings: Aluminum: use AL/CU-listed terminations and anti-oxidant compound.
Wire sizing derivation
Load: 100A at 240V (single-phase), 75 ft, aluminum at 75°C
Step 1 — Ampacity: find smallest wire where derated ampacity ≥ 100A → 1 AWG (base 100A, no derating)
Step 2 — Voltage drop: allowed VD = 240V × 2% = 4.8V
CM = (2 × 21.2 × 100A × 75ft) / 4.8V = 66,250 CM → 2 AWG
Step 3 — Recommended: 1 AWG (ampacity governs)
Breaker: NEC 240.6(A): use 100A breaker (next standard size ≥ 100A)
Ground wire: NEC Table 250.122: 100A OCPD → EGC ≥ 8 AWG Cu (or 6 AWG Al)
Power loss: 372W in run — ~3258.7 kWh/yr (~$456.22/yr @ $0.14/kWh)
Cost: ~$3.2/ft × 150 ft = ~$480 (2024 retail THHN)
Conduit: minimum 2" EMT for 3 conductors of 1 AWG
Verification: 100A ≥ 100A ✓ | VD 1.58% ≤ 2% ✓
Preset wire sizing FAQ
Can I use this preset for every residential project?
No. The preset is a high-confidence planning model for a common setup, but equipment nameplate values, local code, and installation conditions can override it.
No. The preset is a high-confidence planning model for a common setup, but equipment nameplate values, local code, and installation conditions can override it.
Why does distance change wire size?
Longer runs increase circuit resistance and voltage drop, so the same amperage can require a larger conductor at longer distances.
Longer runs increase circuit resistance and voltage drop, so the same amperage can require a larger conductor at longer distances.
Can aluminum replace copper in this preset?
Only with AL-rated terminations and approved installation methods. Use the material alternatives table to compare gauge, ampacity, voltage drop, and cost.
Only with AL-rated terminations and approved installation methods. Use the material alternatives table to compare gauge, ampacity, voltage drop, and cost.
What field details must be checked?
Confirm breaker size, conductor material, insulation, terminal temperature, raceway fill, conductor count, ambient temperature, wet-location rules, and local amendments.
Confirm breaker size, conductor material, insulation, terminal temperature, raceway fill, conductor count, ambient temperature, wet-location rules, and local amendments.
Other common circuits
Kitchen Outlet Circuit (20A, 120V)10 AWG copper20A • 120V • 50ftElectric Dryer (30A, 240V)10 AWG copper30A • 240V • 25ftEV Charger Level 2 (50A, 240V)8 AWG copper50A • 240V • 50ftElectric Range / Oven (50A, 240V)6 AWG copper50A • 240V • 25ftHot Tub / Spa (50A, 240V)8 AWG copper50A • 240V • 60ftWorkshop Tool Circuit (30A, 240V)10 AWG copper30A • 240V • 75ft