Improvements to PVWatts for Fixed and One-Axis Tracking Systems

Research output: Contribution to conferencePaper

3 Scopus Citations


This work presents improvements to the widely used NREL PVWatts photovoltaic system energy model to improve modeling accuracy for typical fixed and one axis system designs. The aim is to calculate losses in the PV system assuming typical modern system design practices, while maintaining simplicity by keeping the required set of input parameters small. These improvements allow users to more credibly and quickly evaluate competing system designs in early stage feasibility. Common submodels for module cover, spectral, snow, tracker, transformer, plant controller, and self-shading losses, in addition to a bifacial gain option, are incorporated into the PVWatts model, and are shown to improve PVWatts' system performance prediction capabilities without major impact to ease of use. We anticipate including these improvements in a future release of NREL's open source PVWatts code, and some of the features may become available in the System Advisor Model (SAM) desktop software as well as the popular PVWatts web application.
Original languageAmerican English
Number of pages6
StatePublished - 2020
Event2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, Illinois
Duration: 16 Jun 201921 Jun 2019


Conference2019 IEEE 46th Photovoltaic Specialists Conference (PVSC)
CityChicago, Illinois

Bibliographical note

See NREL/CP-6A20-74097 for preprint

NREL Publication Number

  • NREL/CP-6A20-76289


  • bifacial
  • photovoltaic modeling
  • PVWatts
  • self-shading


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