10 AWG Solar Installation Wire Run-Length and Power-Loss Cheat Sheet

Why Voltage Drop Matters

• Efficiency & Output: The longer the wire and the higher the current, the more voltage (and power) you lose before energy reaches your inverter, charge controller, or battery bank.
• Low Voltage = Higher % Loss: At 12 V or 24 V, dropping even a few volts can represent a large percentage of the total.
• Higher Current or Longer Distances = Bigger Losses: Doubling distance roughly doubles voltage drop. Increasing current also increases drop proportionally.

Key Assumptions & Notes

1. Wire Specs:
   • Based on Solar Super Sonic 10AWG (UL4703, 2 kV) PV wire with max. resistance @ 1.01 Ω per 1000 ft.10 AWG
2. Distances:
   • One-way: 6 ft, 10 ft, 20 ft, 30 ft, 50 ft, 100 ft, 150 ft, 200 ft, 400 ft.
   • Round-trip distance = 2 × (one-way).
3. Currents:
   • Showcasing with 5 A, 10 A, 15 A, 20 A, and 30 A systems. Actual current will vary by scenario. Wire gauges should be calculated using maximum anticipated currents and should be protected with fuses or other safety devices
4. Voltage Drop Formula: $$V_{\text{drop}} \;=\; I \;\times\; \bigl(1.01\;\Omega / 1000\,\text{ft}\bigr)\;\times\;\frac{\text{Round-Trip Distance (ft)}}{1000}$$
5. Percentage Drop: $$\%\text{Drop} \;=\;\Bigl(\frac{V_{\text{drop}}}{V_{\text{system}}}\Bigr)\times 100\%$$ Columns cover 12 V, 24 V, 48 V, 100 V, 240 V, 600 V, 1000 V, 1500 V.
6. When % Drop > 100
   • We mark it as “>99%” in that column.
7. Real-World Caveats:
   • Real-world factors (e.g., temperature, humidity) will impact the actual voltage drop.
     
   • Always follow local and national electrical codes (e.g. NEC in the U.S.) for safe and compliant installations.
   • Large voltage drops can often be mitigated by shortening cable runs, using thicker wire, or raising system voltage (e.g. from 12 V to 48 V or higher).

Table A: 10 AWG @ 5 A

Table B: 10 AWG @ 10 A

Table C: 10 AWG @ 15 A

Table D: 10 AWG @ 20 A

Table E: 10 AWG @ 30 A

Table F (40 A)

Conclusions & Tips

1. Lower Voltages Suffer Most: At 12 V or 24 V, even moderate distances can push drops above 10–20% quickly, especially at high currents (30–40 A).
2. Higher Voltage = Lower % Loss: The same voltage drop is a much smaller fraction at 48 V, 100 V, or beyond.
3. Watch for >99%: If the voltage drop exceeds your system voltage, it’s effectively impossible to operate that circuit at design specs.
4. Consider Thicker Wire or Shorter Runs: If you see unacceptably high drops, 8 AWG (or thicker) might be necessary, or place your equipment closer to the array/battery.
5. Code Compliance: Always verify you meet NEC ampacity and other local requirements—voltage drop is only one part of a safe, legal solar installation.

Use this cheat sheet as a quick reference. Generally, NEC recommends a voltage drop of 3% or less. If you spot large losses at your planned current and distance, you’ll likely need to upgrade wire gauge, raise system voltage, or shorten cable runs to preserve efficiency and stay within best-practice voltage-drop limits.