Solar Voltage Drop
DC voltage drop compounds differently over a system’s lifetime than a typical AC circuit — a reason installers treat it especially seriously.
A general AC circuit with a 3% voltage drop is a compliance figure, checked once at design time. A solar DC circuit with a 3% voltage drop is a production loss that repeats every single sunny hour, every single day, for the system's entire operating life — which is exactly why solar installers hold DC voltage drop to a tighter standard than general AC wiring.
A 2% voltage drop in a DC string cable means roughly 2% less energy reaching the inverter than the array actually produced, every day, for 25+ years. On a commercial-scale system, that seemingly small percentage adds up to a genuinely significant amount of lost lifetime energy production — and lost revenue, on a system built to generate income.
Unlike a general AC circuit where "compliant" is the whole goal, DC solar cable sizing has a real financial argument for going beyond the minimum compliant size on longer runs — the additional cable cost can be recovered through improved lifetime energy yield, particularly on commercial-scale runs exceeding a modest length.
Check your run's actual voltage drop percentage in the PV/Solar DC Cable Sizing calculators before deciding the minimum-compliant size is automatically the right economic choice.
Engr. Jason Morales — Founder, SolarEnergyPH & OhmWorks