Solar Cable Sizing: PV Wire Gauge & Voltage Drop Guide
12 min
Check string compatibility, find matching panels for your inverter, or find replacements for existing panels — no engineering degree required.
Choose your solar panel and inverter from our database of 100+ models, or upload a datasheet to add your own.
Enter the coldest winter and hottest summer temperatures for your location. We adjust voltage and current accordingly.
See a clear pass/warning/fail result for 7 safety checks based on IEC 62548 and NEC 690.7 standards.
Voltage limits, MPPT range, current capacity — every critical parameter is verified against manufacturer specifications.
Solar panels produce more voltage in cold weather and more current in hot weather. We account for both extremes.
Pre-loaded database with panels and inverters from major manufacturers. Upload a datasheet to add any missing model.
Results appear as you type. No account required for basic calculations. Free and open to everyone.
If the open-circuit voltage of your panel string exceeds the inverter's maximum DC input voltage, the inverter can be permanently damaged. This is most dangerous in cold weather when panel voltage is highest. Our calculator checks this at your coldest expected temperature.
Solar panels produce higher voltage in cold weather and lower voltage in hot weather. The rate of change is specified by the temperature coefficient of Voc (typically around -0.27%/°C). At -20°C, a panel rated at 40V can reach over 45V. This is why temperature-adjusted calculations are essential for safety.
The maximum number depends on your inverter's voltage limits and your local temperatures. You need the string voltage to stay below the inverter's max DC voltage in cold weather, and above the MPPT minimum voltage in hot weather. Our calculator finds the safe range for your specific equipment.
MPPT (Maximum Power Point Tracking) is the voltage range where your inverter operates most efficiently. If your string voltage falls outside this range, the inverter either shuts down (below minimum) or clips power (above maximum). Staying within the MPPT range ensures maximum energy harvest.
Pre-configured kits from reputable manufacturers are usually designed to be compatible. However, if you're mixing brands, changing the number of panels, or installing in a climate with extreme temperatures, a compatibility check is strongly recommended.
Voc (open-circuit voltage) is the maximum voltage a panel produces when not connected to a load — it's important for safety limits. Vmpp (voltage at maximum power point) is the typical operating voltage when the panel is generating power. Vmpp is always lower than Voc. Your string Voc must stay below the inverter's max DC voltage, while Vmpp should stay within the MPPT range.
Mixing different panels in a series string is generally not recommended. Panels with different current ratings will be limited by the weakest panel, reducing overall output. If you must mix, panels should have the same short-circuit current (Isc). Different panels can safely be connected to separate MPPT inputs on the inverter.
Multiple MPPT (Maximum Power Point Tracking) inputs allow your inverter to independently optimize power from different groups of panels. This is useful when panels face different directions (east/west split), have different tilt angles, or experience partial shading. Each MPPT input tracks its own optimal voltage independently, maximizing total energy harvest.
