Selecting the correct wire gauge for your solar installation ensures safety, minimizes voltage drop, and prevents energy waste. This reference covers copper conductor AWG sizes from 14 gauge through 4/0, with ampacity ratings at different temperature classes and pre-calculated sizing charts for 12V and 48V DC systems.
For a custom calculation with your specific current, distance, and voltage, use our free wire gauge calculator.
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AWG Wire Gauge Amp Rating Table (Copper)
Ampacity values per NEC Table 310.16. Round-trip resistance in ohms per 1,000 feet.
| AWG | Diameter (mm) | Resistance (/1000ft) | 60°C | 75°C | 90°C | Typical Solar Use |
|---|---|---|---|---|---|---|
| 14 | 1.63 | 2.525 Ω | 15A | 15A | 15A | Light circuits, 15A breakers |
| 12 | 2.05 | 1.588 Ω | 20A | 20A | 20A | General circuits, 20A breakers |
| 10 | 2.59 | 0.999 Ω | 30A | 30A | 30A | Large appliances, 30A breakers, small PV strings |
| 8 | 3.26 | 0.628 Ω | 40A | 40A | 45A | Subpanels, EV chargers, MPPT output |
| 6 | 4.11 | 0.395 Ω | 55A | 55A | 60A | AC disconnects, combiner outputs |
| 4 | 5.19 | 0.249 Ω | 70A | 70A | 80A | Service entrance, battery cables |
| 3 | 5.83 | 0.197 Ω | 85A | 85A | 100A | Large inverter DC connections |
| 2 | 6.54 | 0.156 Ω | 95A | 95A | 115A | High-current battery banks |
| 1 | 7.35 | 0.124 Ω | 110A | 110A | 130A | Battery-to-inverter runs |
| 1/0 | 8.25 | 0.098 Ω | 125A | 125A | 150A | Large battery banks, main DC feeds |
| 2/0 | 9.27 | 0.078 Ω | 145A | 145A | 175A | High-current DC distribution |
| 3/0 | 10.4 | 0.062 Ω | 165A | 165A | 200A | Large off-grid inverters |
| 4/0 | 11.68 | 0.049 Ω | 195A | 195A | 230A | High-power commercial systems |
75°C column (THWN/THHN) is most commonly used for solar installations. Always derate for conduit fill, ambient temperature, and bundling per NEC.
48 Volt DC Wire Size Chart
Recommended copper AWG gauge by current and one-way distance. Based on 3% maximum voltage drop at 48VDC.
| Current | 10 ft | 20 ft | 30 ft | 50 ft | 75 ft | 100 ft |
|---|---|---|---|---|---|---|
| 10A | 14 | 14 | 12 | 10 | 8 | 6 |
| 20A | 12 | 10 | 8 | 6 | 4 | 3 |
| 30A | 10 | 8 | 6 | 4 | 2 | 1 |
| 50A | 8 | 6 | 4 | 2 | 1/0 | 2/0 |
| 75A | 6 | 4 | 2 | 1/0 | 2/0 | 4/0 |
| 100A | 4 | 2 | 1 | 2/0 | 4/0 | 4/0* |
* May require parallel conductors or higher voltage system. Values are AWG gauge for copper at 3% voltage drop.
12 Volt DC Wire Size Chart
Recommended copper AWG gauge for 12V DC systems (RV, marine, small off-grid). Based on 3% maximum voltage drop.
| Current | 10 ft | 20 ft | 30 ft | 50 ft | 75 ft | 100 ft |
|---|---|---|---|---|---|---|
| 5A | 14 | 12 | 10 | 8 | 6 | 4 |
| 10A | 12 | 10 | 8 | 6 | 4 | 2 |
| 20A | 10 | 8 | 6 | 4 | 2 | 1 |
| 30A | 8 | 6 | 4 | 2 | 1/0 | 2/0 |
| 50A | 6 | 4 | 2 | 1/0 | 3/0 | 4/0 |
| 75A | 4 | 2 | 1/0 | 3/0 | 4/0* | 4/0* |
* May require parallel conductors. 12V systems require much heavier wire than 48V for the same power — this is why 48V is preferred for larger installations.
How to Calculate Voltage Drop
The voltage drop formula for DC circuits is:
Vdrop = (2 x Length x Current x Resistance) / 1000
Where Length = one-way distance in feet, Resistance = ohms per 1,000 ft from the AWG table
Then calculate the percentage: Vdrop / System Voltage x 100
NEC recommends keeping voltage drop under 3% for branch circuits and 5% total for the entire system from source to load.
Example: Battery to Inverter at 48V
Current: 100A | Distance: 6 feet | Wire: 4/0 AWG (0.049 ohms/1000ft)
Vdrop = (2 x 6 x 100 x 0.049) / 1000 = 0.059V
Percentage = 0.059 / 48 x 100 = 0.12% (excellent)
Wire Sizing Tips for Solar Installations
Use 48V When Possible
At the same power level, 48V circuits carry 1/4 the current of 12V. This means dramatically smaller (and cheaper) wire. A 1,200W load needs 100A at 12V but only 25A at 48V.
Keep Battery Cables Short
Battery-to-inverter connections carry the highest current in the system. Keep these runs under 10 feet and use the largest practical gauge. Most inverter manufacturers specify minimum wire sizes in their manuals.
Size for 80% of Breaker Rating
NEC requires continuous loads (running 3+ hours) to be limited to 80% of the conductor's ampacity. A 30A breaker on a continuous circuit should use wire rated for at least 37.5A (use 10 AWG or larger).
PV Wire vs THWN
Solar panel strings exposed to sunlight require PV Wire (USE-2) rated for wet and UV conditions. THWN/THHN is fine for conduit runs indoors. Don't use standard romex for DC circuits.
Calculate Your Exact Wire Size
Enter your specific current, distance, and voltage for a precise wire gauge recommendation with voltage drop analysis.
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