Solar

Solar String Size Calculator

Calculate the minimum and maximum number of solar panels that can be connected in series per inverter string.

Solar Panel

Panel Voc

Panel Vmp

Find Voc and Vmp on the solar module datasheet.

Inverter / MPPT

Maximum DC Input Voltage

Minimum MPPT Voltage

Use the inverter manufacturer’s DC input specifications.

Cold-Weather Check

Minimum Site Temperature

°C

Voc Temperature Coefficient

%/°C

Enter the Voc temperature coefficient exactly as shown on the module datasheet. It is normally a negative value.

Panels Per String

—

Preliminary series-string range based on the panel, inverter and temperature conditions entered.

Maximum Panels Per String —

Minimum Panels Per String —

Cold-Corrected Panel Voc —

Maximum Cold String Voc —

String Connection Diagram

Minimum String

Maximum String

How it is calculated: Panel open-circuit voltage is corrected for the entered minimum temperature using the module’s Voc temperature coefficient. Maximum panels per string = inverter maximum DC voltage ÷ cold-corrected panel Voc, rounded down. Minimum panels per string = inverter minimum MPPT voltage ÷ panel Vmp, rounded up. The maximum-string calculation helps prevent excessive DC voltage during cold conditions. The minimum-string result is a simplified STC-based MPPT check. Final design should also verify the inverter’s full MPPT operating range at expected module temperatures, maximum input current, short-circuit-current limit and manufacturer string-design requirements.