8 AWG Solar Installation Run-Length and Power-Loss Cheat Sheet
Why Voltage Drop Matters
- Efficiency: The farther electricity travels through wire, the more energy is lost as heat.
- Low Voltage = Higher % Loss: In 12 V or 24 V systems, even a small voltage drop can be a large percentage of the total.
- High Current or Long Distance: Doubling the cable length or current roughly doubles the voltage drop.
Key Parameters & Disclaimers
- Wire Resistance: Based on 8 AWG UL4703 PV Wire from Solar Super Sonic @0.63 Ω per 1000 ft.
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Distance Listing: One-way distances of 6, 10, 20, 30, 50, 100, 150, 200, 400 ft.
- Round-trip distance = 2 × (one-way).
- 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
- Voltage Drop Formula:
- Percentage Drop: We use columns for 12 V, 24 V, 48 V, 100 V, 240 V, 600 V, 1000 V, and 1500 V.
- When Drop >100%: Marked as “>99%” in that cell.
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Real-World Caveats:
- These tables ignore temperature effects, conduit fill, code-minimum ampacity rules, etc.
- Always follow local electrical codes (NEC, etc.) for a safe and compliant design.
- If you see large voltage-drop percentages, you may need a higher system voltage, thicker wire, or shorter runs to maintain efficiency.
Table A: 8 AWG @ 5 A
Voltage Drop = 5 A × 0.63 Ω/1000 ft × (Round-Trip ft / 1000)
| One-Way (ft) | Round-Trip (ft) | V_drop (V) | % @12 V | % @24 V | % @48 V | % @100 V | % @240 V | % @600 V | % @1000 V | % @1500 V |
|---|---|---|---|---|---|---|---|---|---|---|
| 6 | 12 | 0.04 | 0.33% | 0.17% | 0.08% | 0.04% | 0.02% | 0.01% | 0.00% | 0.00% |
| 10 | 20 | 0.06 | 0.50% | 0.25% | 0.13% | 0.06% | 0.03% | 0.01% | 0.01% | 0.00% |
| 20 | 40 | 0.13 | 1.04% | 0.52% | 0.26% | 0.13% | 0.05% | 0.02% | 0.01% | 0.01% |
| 30 | 60 | 0.19 | 1.58% | 0.79% | 0.40% | 0.19% | 0.08% | 0.03% | 0.02% | 0.01% |
| 50 | 100 | 0.32 | 2.63% | 1.32% | 0.66% | 0.32% | 0.13% | 0.05% | 0.03% | 0.02% |
| 100 | 200 | 0.63 | 5.25% | 2.63% | 1.31% | 0.63% | 0.26% | 0.11% | 0.06% | 0.04% |
| 150 | 300 | 0.95 | 7.92% | 3.96% | 1.98% | 0.95% | 0.40% | 0.16% | 0.10% | 0.06% |
| 200 | 400 | 1.26 | 10.50% | 5.25% | 2.63% | 1.26% | 0.53% | 0.21% | 0.13% | 0.08% |
| 400 | 800 | 2.52 | 21.00% | 10.50% | 5.25% | 2.52% | 1.05% | 0.42% | 0.25% | 0.17% |
Table B: 8 AWG @ 10 A
Voltage Drop = 10 A × 0.63 Ω/1000 ft × (Round-Trip ft / 1000)
| One-Way (ft) | Round-Trip (ft) | V_drop (V) | % @12 V | % @24 V | % @48 V | % @100 V | % @240 V | % @600 V | % @1000 V | % @1500 V |
|---|---|---|---|---|---|---|---|---|---|---|
| 6 | 12 | 0.08 | 0.67% | 0.33% | 0.17% | 0.08% | 0.03% | 0.01% | 0.01% | 0.01% |
| 10 | 20 | 0.13 | 1.04% | 0.52% | 0.26% | 0.13% | 0.05% | 0.02% | 0.01% | 0.01% |
| 20 | 40 | 0.25 | 2.08% | 1.04% | 0.52% | 0.25% | 0.10% | 0.04% | 0.03% | 0.02% |
| 30 | 60 | 0.38 | 3.17% | 1.58% | 0.79% | 0.38% | 0.16% | 0.06% | 0.04% | 0.03% |
| 50 | 100 | 0.63 | 5.25% | 2.63% | 1.31% | 0.63% | 0.26% | 0.11% | 0.06% | 0.04% |
| 100 | 200 | 1.26 | 10.50% | 5.25% | 2.63% | 1.26% | 0.53% | 0.21% | 0.13% | 0.08% |
| 150 | 300 | 1.89 | 15.75% | 7.88% | 3.94% | 1.89% | 0.79% | 0.32% | 0.19% | 0.13% |
| 200 | 400 | 2.52 | 21.00% | 10.50% | 5.25% | 2.52% | 1.05% | 0.42% | 0.25% | 0.17% |
| 400 | 800 | 5.04 | 42.00% | 21.00% | 10.50% | 5.04% | 2.10% | 0.84% | 0.50% | 0.34% |
Table C: 8 AWG @ 15 A
Voltage Drop = 15 A × 0.63 Ω/1000 ft × (Round-Trip ft / 1000)
| One-Way (ft) | Round-Trip (ft) | V_drop (V) | % @12 V | % @24 V | % @48 V | % @100 V | % @240 V | % @600 V | % @1000 V | % @1500 V |
|---|---|---|---|---|---|---|---|---|---|---|
| 6 | 12 | 0.12 | 1.00% | 0.50% | 0.25% | 0.12% | 0.05% | 0.02% | 0.01% | 0.01% |
| 10 | 20 | 0.19 | 1.58% | 0.79% | 0.40% | 0.19% | 0.08% | 0.03% | 0.02% | 0.01% |
| 20 | 40 | 0.38 | 3.17% | 1.58% | 0.79% | 0.38% | 0.16% | 0.06% | 0.04% | 0.03% |
| 30 | 60 | 0.57 | 4.75% | 2.38% | 1.19% | 0.57% | 0.24% | 0.10% | 0.06% | 0.04% |
| 50 | 100 | 0.95 | 7.92% | 3.96% | 1.98% | 0.95% | 0.40% | 0.16% | 0.10% | 0.06% |
| 100 | 200 | 1.89 | 15.75% | 7.88% | 3.94% | 1.89% | 0.79% | 0.32% | 0.19% | 0.13% |
| 150 | 300 | 2.83 | 23.58% | 11.79% | 5.90% | 2.83% | 1.18% | 0.47% | 0.28% | 0.19% |
| 200 | 400 | 3.78 | 31.50% | 15.75% | 7.88% | 3.78% | 1.58% | 0.63% | 0.38% | 0.25% |
| 400 | 800 | 7.56 | 63.00% | 31.50% | 15.75% | 7.56% | 3.15% | 1.26% | 0.76% | 0.50% |
Table D: 8 AWG @ 20 A
Voltage Drop = 20 A × 0.63 Ω/1000 ft × (Round-Trip ft / 1000)
| One-Way (ft) | Round-Trip (ft) | V_drop (V) | % @12 V | % @24 V | % @48 V | % @100 V | % @240 V | % @600 V | % @1000 V | % @1500 V |
|---|---|---|---|---|---|---|---|---|---|---|
| 6 | 12 | 0.15 | 1.25% | 0.63% | 0.31% | 0.15% | 0.06% | 0.03% | 0.02% | 0.01% |
| 10 | 20 | 0.25 | 2.08% | 1.04% | 0.52% | 0.25% | 0.10% | 0.04% | 0.03% | 0.02% |
| 20 | 40 | 0.50 | 4.17% | 2.08% | 1.04% | 0.50% | 0.21% | 0.08% | 0.05% | 0.03% |
| 30 | 60 | 0.76 | 6.33% | 3.17% | 1.58% | 0.76% | 0.32% | 0.13% | 0.08% | 0.05% |
| 50 | 100 | 1.26 | 10.50% | 5.25% | 2.63% | 1.26% | 0.53% | 0.21% | 0.13% | 0.08% |
| 100 | 200 | 2.52 | 21.00% | 10.50% | 5.25% | 2.52% | 1.05% | 0.42% | 0.25% | 0.17% |
| 150 | 300 | 3.78 | 31.50% | 15.75% | 7.88% | 3.78% | 1.58% | 0.63% | 0.38% | 0.25% |
| 200 | 400 | 5.04 | 42.00% | 21.00% | 10.50% | 5.04% | 2.10% | 0.84% | 0.50% | 0.34% |
| 400 | 800 | 10.08 | 84.00% | 42.00% | 21.00% | 10.08% | 4.20% | 1.68% | 1.01% | 0.67% |
Table E: 8 AWG @ 30 A
Voltage Drop = 30 A × 0.63 Ω/1000 ft × (Round-Trip ft / 1000)
| One-Way (ft) | Round-Trip (ft) | V_drop (V) | % @12 V | % @24 V | % @48 V | % @100 V | % @240 V | % @600 V | % @1000 V | % @1500 V |
|---|---|---|---|---|---|---|---|---|---|---|
| 6 | 12 | 0.19 | 1.58% | 0.79% | 0.40% | 0.19% | 0.08% | 0.03% | 0.02% | 0.01% |
| 10 | 20 | 0.38 | 3.17% | 1.58% | 0.79% | 0.38% | 0.16% | 0.06% | 0.04% | 0.03% |
| 20 | 40 | 0.76 | 6.33% | 3.17% | 1.58% | 0.76% | 0.32% | 0.13% | 0.08% | 0.05% |
| 30 | 60 | 1.13 | 9.50% | 4.75% | 2.38% | 1.13% | 0.47% | 0.19% | 0.11% | 0.08% |
| 50 | 100 | 1.89 | 15.75% | 7.88% | 3.94% | 1.89% | 0.79% | 0.32% | 0.19% | 0.13% |
| 100 | 200 | 3.78 | 31.50% | 15.75% | 7.88% | 3.78% | 1.58% | 0.63% | 0.38% | 0.25% |
| 150 | 300 | 5.67 | 47.25% | 23.63% | 11.81% | 5.67% | 2.36% | 0.94% | 0.57% | 0.38% |
| 200 | 400 | 7.56 | 63.00% | 31.50% | 15.75% | 7.56% | 3.15% | 1.26% | 0.76% | 0.50% |
| 400 | 800 | 15.12 | >99% | 63.00% | 31.50% | 15.12% | 6.30% | 2.52% | 1.51% | 1.01% |
Table F: 8 AWG @ 40 A
Voltage Drop = 40 A × 0.63 Ω/1000 ft × (Round-Trip ft / 1000)
| One-Way (ft) | Round-Trip (ft) | V_drop (V) | % @12 V | % @24 V | % @48 V | % @100 V | % @240 V | % @600 V | % @1000 V | % @1500 V |
|---|---|---|---|---|---|---|---|---|---|---|
| 6 | 12 | 0.25 | 2.08% | 1.04% | 0.52% | 0.25% | 0.10% | 0.04% | 0.03% | 0.02% |
| 10 | 20 | 0.50 | 4.17% | 2.08% | 1.04% | 0.50% | 0.21% | 0.08% | 0.05% | 0.03% |
| 20 | 40 | 1.01 | 8.42% | 4.21% | 2.11% | 1.01% | 0.42% | 0.17% | 0.10% | 0.07% |
| 30 | 60 | 1.51 | 12.58% | 6.29% | 3.15% | 1.51% | 0.63% | 0.25% | 0.15% | 0.10% |
| 50 | 100 | 2.52 | 21.00% | 10.50% | 5.25% | 2.52% | 1.05% | 0.42% | 0.25% | 0.17% |
| 100 | 200 | 5.04 | 42.00% | 21.00% | 10.50% | 5.04% | 2.10% | 0.84% | 0.50% | 0.34% |
| 150 | 300 | 7.56 | 63.00% | 31.50% | 15.75% | 7.56% | 3.15% | 1.26% | 0.76% | 0.50% |
| 200 | 400 | 10.08 | 84.00% | 42.00% | 21.00% | 10.08% | 4.20% | 1.68% | 1.01% | 0.67% |
| 400 | 800 | 20.16 | >99% | 84.00% | 42.00% | 20.16% | 8.40% | 3.36% | 2.02% | 1.35% |
Table G: 8 AWG @ 50 A
Voltage Drop = 50 A × 0.63 Ω/1000 ft × (Round-Trip ft / 1000)
| One-Way (ft) | Round-Trip (ft) | V_drop (V) | % @12 V | % @24 V | % @48 V | % @100 V | % @240 V | % @600 V | % @1000 V | % @1500 V |
|---|---|---|---|---|---|---|---|---|---|---|
| 6 | 12 | 0.31 | 2.58% | 1.29% | 0.65% | 0.31% | 0.13% | 0.05% | 0.03% | 0.02% |
| 10 | 20 | 0.63 | 5.25% | 2.63% | 1.31% | 0.63% | 0.26% | 0.11% | 0.06% | 0.04% |
| 20 | 40 | 1.26 | 10.50% | 5.25% | 2.63% | 1.26% | 0.53% | 0.21% | 0.13% | 0.08% |
| 30 | 60 | 1.89 | 15.75% | 7.88% | 3.94% | 1.89% | 0.79% | 0.32% | 0.19% | 0.13% |
| 50 | 100 | 3.15 | 26.25% | 13.13% | 6.56% | 3.15% | 1.31% | 0.53% | 0.31% | 0.21% |
| 100 | 200 | 6.30 | 52.50% | 26.25% | 13.13% | 6.30% | 2.63% | 1.05% | 0.63% | 0.42% |
| 150 | 300 | 9.45 | 78.75% | 39.38% | 19.69% | 9.45% | 3.94% | 1.58% | 0.95% | 0.63% |
| 200 | 400 | 12.60 | >99% | 52.50% | 26.25% | 12.60% | 5.25% | 2.10% | 1.26% | 0.84% |
| 400 | 800 | 25.20 | >99% | >99% | 52.50% | 25.20% | 10.50% | 4.20% | 2.52% | 1.68% |
Final Thoughts
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At Lower Voltages (12 V or 24 V): It doesn’t take much distance or current for voltage drop to reach double-digit percentages. If you see large drops, you may need to:
- Raise system voltage (e.g., 48 V or 100 V).
- Use thicker wire (or shorter runs) to stay under 2–3% recommended drop.
- High-Current Circuits: Especially at 30 A, 40 A, or 50 A, ensure your wire is also code-legal for ampacity and temperature limits, not just voltage drop.
- Always Check Codes: The NEC or other local regulations may require heavier gauge wire for safe operation beyond just voltage-drop considerations.
Use these tables to quickly gauge whether 8 AWG meets your solar wiring needs at a given run length, current, and system voltage. NEC recommends a voltage drop of 3% or less. If higher drops observed than desired, it’s time to upgrade wire size, raise voltage, or shorten runs for a more efficient, code-compliant solar installation.
