DC Wire Size (Solar / RV / Marine)
Low-voltage DC wire sizing for 12V, 24V and 48V systems. At low voltage, voltage drop almost always sets the wire size — pick your system voltage, current and run length.
12V DC wire size (at 20 ft, ≤3% drop)
24V DC wire size (at 20 ft, ≤3% drop)
48V DC wire size (at 20 ft, ≤3% drop)
Copper, ≤3% voltage drop over the listed one-way distance (round-trip in the math). For solar, size conductors and fuses to 125% per NEC 690.8. Reference only.