Heavy-duty wire for 70-85 amp applications: large sub-panels, commercial EV chargers, and industrial equipment.
| Wire Gauge | 4 AWG |
| Diameter (inches) | 0.2043 in |
| Diameter (mm) | 5.189 mm |
| Cross-sectional Area | 21.15 mm² (41,740 circular mils) |
| Copper Resistance | 0.8152 Ω/1000ft (2.67 Ω/km) @ 20°C |
| Copper Ampacity (60°C) | 70A |
| Copper Ampacity (75°C) | 85A |
| Copper Ampacity (90°C) | 95A |
| Max Circuit Breaker | 70-80A (depending on installation) |
70-80A sub-panels for large garages, workshops, or accessory dwelling units (ADUs).
High-power Level 2 chargers (60A+) and Tesla destination chargers at commercial locations.
Large motors, industrial HVAC systems, and heavy machinery requiring 70-80A circuits.
Small residential service entrances (typically use SE cable or THHN in conduit).
Solar battery storage systems and backup power installations with high current requirements.
Large welders (60A+), plasma cutters, and heavy-duty shop equipment.
| Property | 4 AWG Copper | 4 AWG Aluminum |
|---|---|---|
| Ampacity (75°C) | 85A | 65A |
| Resistance | 0.249 Ω/1000ft | 0.409 Ω/1000ft |
| Weight | Heavier | ~30% lighter |
| Cost (per 100ft) | ~$200-280 | ~$80-120 |
| Best For | Space-limited, max performance | Long runs, budget-conscious |
Important: For equivalent ampacity to 4 AWG copper (85A), use 2 AWG aluminum. Always use aluminum-rated terminals and anti-oxidant compound with aluminum wire.
Use our calculator to determine the right wire size for your feeder installation.
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