Wire & Fuse Size Charts
Proper wire and fuse sizing is critical for the safety and efficiency of any DC electrical system. Use the charts below as a general reference for standard 12V and 24V mobile solar installations.
Note: These charts are for reference only. Always consult specific manufacturer documentation, local codes, and consider ambient temperatures or wire bundling, which can derate wire capacities.
Standard DC Wire Sizing Guide
The table below shows the maximum recommended continuous amperage and suggested fuse sizes for common marine-grade (105°C rated) copper wire. Lengths represent the maximum round-trip distance (positive + negative) to maintain a voltage drop of 3% or less.
| Wire Gauge (AWG) | Max Amps (105°C) | Recommended Fuse | Max Length @ 12V (3% drop) | Max Length @ 24V (3% drop) |
|---|---|---|---|---|
| 16 AWG | 25A | 20A | 11 ft @ 10A | 22 ft @ 10A |
| 14 AWG | 35A | 30A | 18 ft @ 10A | 36 ft @ 10A |
| 12 AWG | 45A | 40A | 14 ft @ 20A | 28 ft @ 20A |
| 10 AWG | 60A | 50A | 15 ft @ 30A | 30 ft @ 30A |
| 8 AWG | 80A | 70A | 15 ft @ 50A | 30 ft @ 50A |
| 6 AWG | 120A | 100A | 12 ft @ 100A | 24 ft @ 100A |
| 4 AWG | 160A | 150A | 13 ft @ 150A | 26 ft @ 150A |
| 2 AWG | 210A | 200A | 16 ft @ 200A | 32 ft @ 200A |
| 1/0 AWG | 285A | 250A - 300A | 16 ft @ 250A | 32 ft @ 250A |
| 2/0 AWG | 330A | 300A - 350A | 16 ft @ 300A | 32 ft @ 300A |
| 4/0 AWG | 445A | 400A | 19 ft @ 400A | 38 ft @ 400A |
Best Practices
- Size for Voltage Drop: For critical loads, size your wire to maintain a voltage drop under 3%. For non-critical loads, 10% is generally acceptable, but thicker wire is always safer.
- Fuse the Wire, Not the Appliance: Fuses are designed to protect the wire from melting and causing a fire. Always place the fuse as close to the power source (battery or busbar) as possible.
- Use Stranded Copper: In RVs, vans, and marine environments, always use stranded copper wire (preferably tinned). Solid wire can fatigue and break due to vibrations.