DC Cable Size & Voltage Drop Calculator

Why voltage drop matters

On DC solar homeruns, every volt lost in the cable is a volt your MPPT or charge controller never sees. Beyond the usual 3% planning limit, undersized copper runs hot (I²R loss), which raises insulation temperature and fire risk on roof trenches and long array feeds.

We size for your amp load, one-way length in meters, and max drop target, then snap to the next standard mm² / AWG with enough ampacity for continuous DC.

• Round-trip resistance: panel → controller and return conductor
• Power loss (W) is wasted heat in the cable—size up to stay cool