Solar String Sizing Calculator

Background.

This solar string sizing page is built to bound series-module count using cold open-circuit voltage and hot maximum-power voltage. Cold weather raises module voltage while heat lowers operating voltage, so both inverter maximum and MPPT minimum matter. The implemented convention is “maximum modules = floor(max inverter DC voltage ÷ cold-adjusted Voc); minimum modules = ceil(minimum MPPT voltage ÷ hot-adjusted Vmp).”

The editable entries are adjusted module open-circuit voltage at design cold temperature, adjusted module maximum-power voltage at design hot temperature, inverter maximum dc input voltage, inverter minimum mppt voltage. Use values from the document or measurement that governs this solar string sizing question; the defaults are only the worked fixture below. Use manufacturer temperature coefficients and local design temperatures; current, parallel strings, rapid shutdown and code factors are excluded. If that solar string sizing condition is not true, choose a calculation that models the missing convention.

U.S. Department of Energy, Solar Photovoltaic System Design Basics; modules, strings, inverters and batteries documents the convention or governing rule used here. The solar string sizing output is a transparent scenario under those facts: it does not manufacture an unentered market price, professional determination, carrier quote, legal eligibility finding or locally adopted code value.

What is solar string sizing calculator?

Solar String Sizing is the relationship behind this decision: cold weather raises module voltage while heat lowers operating voltage, so both inverter maximum and MPPT minimum matter. On this page it means maximum modules = floor(max inverter DC voltage ÷ cold-adjusted Voc); minimum modules = ceil(minimum MPPT voltage ÷ hot-adjusted Vmp). Use manufacturer temperature coefficients and local design temperatures; current, parallel strings, rapid shutdown and code factors are excluded; that is the line between the reported quantity and a broader building systems analysis.

How to use this calculator.

1. 01Confirm that “maximum modules = floor(max inverter DC voltage ÷ cold-adjusted Voc); minimum modules = ceil(minimum MPPT voltage ÷ hot-adjusted Vmp)” matches the solar string sizing convention you need.
2. 02Replace the fixture values for adjusted module open-circuit voltage at design cold temperature, adjusted module maximum-power voltage at design hot temperature, inverter maximum dc input voltage, inverter minimum mppt voltage with dated values from the governing record.
3. 03Keep all currencies, measurement units and time periods on the same basis before calculating.
4. 04Read maximum whole modules per string together with this boundary: Use manufacturer temperature coefficients and local design temperatures; current, parallel strings, rapid shutdown and code factors are excluded.

The formula.

The calculation uses maximum modules = floor(max inverter DC voltage ÷ cold-adjusted Voc); minimum modules = ceil(minimum MPPT voltage ÷ hot-adjusted Vmp). In this solar string sizing model, the entered terms are adjusted module open-circuit voltage at design cold temperature, adjusted module maximum-power voltage at design hot temperature, inverter maximum dc input voltage, inverter minimum mppt voltage. Cold weather raises module voltage while heat lowers operating voltage, so both inverter maximum and MPPT minimum matter, which is why the relationship is presented under this name rather than as a universal alternative. Use manufacturer temperature coefficients and local design temperatures; current, parallel strings, rapid shutdown and code factors are excluded. Calculations keep full decimal precision through the relationship and round only the returned display values.

A worked example.

Frequently asked questions.

References& sources.

1. [1]U.S. Department of Energy, Solar Photovoltaic System Design Basics; modules, strings, inverters and batteries. Retrieved 2026-08-07. access: open unless marked otherwise.
2. [2]U.S. Department of Energy. Energy Saver. Retrieved 2026-08-07. independence: primary; access: open.
3. [3]International Code Council. 2024 International Residential Code (IRC). Retrieved 2026-08-07. independence: primary; access: open.