Solar Panel String Calculator

When wiring solar panels together, the string voltage must stay within your inverter's safe operating range across all temperatures — the Solar Panel String Calculator checks exactly that. Enter your panel's rated power, Vmp, Voc, and temperature coefficient, along with your minimum and maximum temperatures, cell temperature rise, and string configuration (panels per string and number of strings). You'll get the maximum string voltage, minimum string voltage, string voltage at max power, total system power, and total panel count.

W
V
V
%/°C

Temperature Scale *

°C
°C
°C

Temperature rise above ambient due to solar irradiation

Results

Maximum String Voltage

--

Minimum String Voltage

--

String Voltage at Max Power

--

Total System Power

--

Total Panels

--

Results Table

More Electrical & Electronics Tools

Frequently Asked Questions

Why is calculating the string voltage so important?

String voltage calculation is critical for solar system safety and performance. If the string voltage exceeds or falls below the inverter's operating range, it can severely reduce system performance or even damage equipment and create fire hazards.

What is the difference between Voc and Vmp in solar panels?

Voc (Open Circuit Voltage) is the maximum voltage when no current flows, while Vmp (Maximum Power Voltage) is the voltage at which the panel produces maximum power. Voc is higher and used for safety calculations, while Vmp determines actual operating voltage.

How does temperature affect solar panel voltage?

Solar panel voltage decreases as temperature increases. Cold temperatures increase voltage (potentially dangerous), while hot temperatures reduce voltage. The temperature coefficient (typically -0.28%/°C) quantifies this relationship.

What is cell temperature rise and why does it matter?

Cell temperature rise is how much warmer solar cells get compared to ambient air temperature due to solar irradiation. Typically 20-30°C above ambient, this affects the actual operating temperature and therefore the panel's voltage output.

How many panels should I put in a string?

The number of panels per string depends on your inverter's voltage range, panel specifications, and local temperature extremes. Generally 8-20 panels per string, but always verify the string voltage stays within inverter limits.

What happens if my string voltage is too high or too low?

If string voltage is too high, it can damage the inverter or create safety hazards. If too low, the inverter may not start or operate efficiently, reducing energy production. Always design strings within the inverter's MPPT voltage range.

Can I mix different solar panels in the same string?

It's not recommended to mix different panel types in the same string as they have different electrical characteristics. This can lead to power losses and reduced system efficiency. Use identical panels within each string.