Glossary Solar PV
Three similar-looking figures on a solar panel datasheet, each feeding into a different part of the DC cable sizing calculation.
A solar panel datasheet lists several electrical figures with similar-looking names. Here's what each one actually feeds into for cable sizing purposes.
The maximum current the panel can produce when its terminals are directly shorted together. This is the figure the 1.25× (or applicable stacked) safety multiplier gets applied to for minimum cable ampacity sizing — see the dedicated 1.25×Isc article.
The actual operating current when the panel is delivering its rated maximum power under normal conditions — lower than Isc. This figure is relevant to voltage drop calculations, since it represents the real, sustained operating current rather than the theoretical short-circuit maximum.
The maximum voltage the panel produces with no current flowing (an open circuit). This figure, corrected for the coldest realistic site temperature (see the dedicated string voltage and temperature article), determines cable and isolator voltage rating requirements.
| Figure | Feeds into |
|---|---|
| Isc | Minimum cable ampacity (with safety multiplier) |
| Imp | Voltage drop calculation (real operating current) |
| Voc | Cable and isolator voltage rating (temperature-corrected) |
Engr. Jason Morales — Founder, SolarEnergyPH & OhmWorks