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Features > Accurate 3D Design > Accuracy Reports


Independently Verified, Class-Leading Design Accuracy

OpenSolar’s founders invented remote solar design 15 years ago.  So we’ve been confident from the start that the reliability and accuracy of OpenSolar’s design tool is second to none.  But we don’t expect you to just take our word for it.  We’ve engaged with some of the most trusted experts in the industry to provide independent, 3rd party assessments of the accuracy of OpenSolar’s design tool.

Shading - think of it as a virtual SunEye

We asked the U.S. Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL), to compare the shading estimates provided by OpenSolar with onsite measurements taken by NREL for eighty-one total points encompassing four
rooftops in Denver, CO and four rooftops in Los Angeles, CA metro areas.


They compared the solar access values provided by OpenSolar with onsite measurements they took using a SunEye.  Here’s what they found:

In aggregate, the results of the analysis show that the annual SAVs provided by OpenSolar were statistically equivalent within ±2.63 SAVs for the four Los Angeles rooftops and within ±2.69 SAVs for the four Denver rooftops, compared to those of the
onsite measurements made by NREL using the SunEye devices.


This has led us to conclude that OpenSolar is now the class-leader in accuracy.

NREL poster.png
Accuracy Reports

Site assessment - like being on the roof

We engaged PVEL, the leading independent lab for the global downstream solar industry, to assess the accuracy of our system-generated site models by taking measurements both in the field and in OpenSolar across a wide range of different shaped and sized roofs.  They found the accuracy of our models to be best-in-class:

  • OpenSolar’s assessment of scale was accurate to within 1 ⅓ feet 100% of the time (no other tool provides as narrow a tolerance)

  • OpenSolar’s assessment of pitch was accurate to within 4 degrees over 97% of the time (no other tool provides as narrow a tolerance OR such high compliance)

Energy modeling - get the basics right

At the core of any solar design tool is energy modeling - how do you convert inputs like pitch azimuth and shading into the key output: production.  OpenSolar’s energy modeling is based on NREL’s most advanced System Advisor Model (SAM).  We engaged with PVEL to validate the integrity of our implementation of SAM, when comparing it to industry standard energy modeling tools like PVsyst or standalone implementations of NREL’s SAM.  PVEL found: 

  • OpenSolar’s energy modeling is consistent with standard engineering practices

  • OpenSolar’s production figures are within 0.0%-0.2% of standalone SAM estimates

  • OpenSolar’s production figures are within 0.1%-1.9% of PVsyst estimates

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