Solar DC Cable Sizing
DC cables are the part of a solar system most likely to be undersized by amateurs — and undersized conductors overheat. Correct gauge is set by two things: how much current flows and how far it travels.
The two runs that matter
Panel to controller: current is lower, voltage higher, but distance is often long — voltage drop is the usual constraint. Battery to inverter: current is very high, so ampacity and voltage drop both matter, and these runs are kept as short as possible.
Why distance doubles the problem
Current travels out and back, so a 5-metre run is 10 metres of conductor. Long runs need thicker cable to keep voltage drop within a few percent — otherwise your panels produce power that never reaches the battery.
Common questions
What is a safe voltage drop?
A common target is under 3% for combined DC runs. Tighter is better for battery-to-inverter runs where currents are high.
Can I use AC cable for DC?
Use cable rated for the application and environment. DC solar runs need appropriate insulation and ampacity — always follow local codes and a licensed contractor.