Double insulated Black & Red Solar Cable

4 mm² (12 AWG) Solar Cable – Current Rating (only per metre)

Typical Ratings (Conservative)

• Continuous current: 25–30 A

• Short-term / peak: up to ~35–40 A (not for continuous operation)

These figures assume:

• Free air or clipped to surface

• Normal ambient temperatures

• Single run (not heavily bundled)

Common applications

• Solar panel strings to MPPT controller

• PV array wiring (roof runs)

• MC4-terminated panel leads

Typical pairing

• 1–2 panels in series or parallel per string

• 15A–20A fuses/breakers per string are common

Most modern solar panels have an Isc (short-circuit current) of ~10–13 A, so 4 mm² cable provides plenty of headroom for a single string.

Installation Factors That Reduce Current Rating

De-rate if any of the following apply:

• High ambient temperatures (roof spaces, summer sun)

• Long cable runs (voltage drop becomes the limiter)

• Multiple cables bundled together

• Conduit without airflow

In these cases, designers often step up to 6 mm² even if current alone would allow 4 mm².

Quick Rule of Thumb

• Single solar string: 4 mm² is ideal

• Parallel strings or long runs: consider 6 mm²

• Continuous loads near 30 A: move up a size