Improvements to PVWatts for Fixed and One-Axis Tracking Systems

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

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 languageEnglish
Title of host publication2019 IEEE 46th Photovoltaic Specialists Conference, PVSC 2019
PublisherInstitute of Electrical and Electronics Engineers Inc.
Number of pages6
ISBN (Electronic)9781728104942
StatePublished - Jun 2019
Event46th IEEE Photovoltaic Specialists Conference, PVSC 2019 - Chicago, United States
Duration: 16 Jun 201921 Jun 2019

Publication series

NameConference Record of the IEEE Photovoltaic Specialists Conference
ISSN (Print)0160-8371


Conference46th IEEE Photovoltaic Specialists Conference, PVSC 2019
Country/TerritoryUnited States

Bibliographical note

Publisher Copyright:
© 2019 IEEE.


  • bifacial
  • energy model
  • NREL
  • photovoltaic modeling
  • PVWatts
  • self-shading


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