One of the most important aspects of designing a solar array is sizing module strings to operate within the parameters of the selected inverter. This is especially true for commercial and megawatt solar projects.

To help in this process, we’re providing a free solar design tool to our readers.

Ryan Mayfield, the Solar PV Technical Editor at SolarPro, and Renewable Energy Associates have developed a free solar design tool to help in that process. Most inverter manufacturers offer some type of sizing tool, but regardless of whether it’s simple or advanced, it’s usually limited to selecting only their products. The REA System Sizing Tool lets you select from a wide variety of products and manufacturers. This tool is used in Ryan Mayfield and SolarPro‘s HeatSpring course called Megawatt Design.

Key Features of the Solar String Sizing Tool

  • Thousands of modules.
  • Hundreds of inverters.
  • Add your own module or inverter.
  • World Wide ASHRAE locations. 5,000+
  • Create your own custom sites.
  • Dual MPPT’s configuration possible.
  • Voltage drop calculator.
  • Performance calculator.
  • Quick Printing features.

Screen Shots of the Solar Design Tool

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 Inserting Weather Conditions

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Logging Other Project Specific Activities



Sign up for Megawatt Design today and spend ten weeks learning from Ryan and other industry leaders. This course is designed to help experienced solar professionals get their projects permitted and installed faster and cheaper. Now you can also receive 30 NABCEP Advanced Credit Hours6 NABCEP Technical/JTA , 6 NABCEP Non-Technical3 NABCEP NEC30 AIA LU/HSW Credits!