Robust PV Degradation Methodology and Application

Dirk Jordan, Christopher Deline, Sarah Kurtz, Gregory Kimball, Mike Anderson

Research output: Contribution to journalArticlepeer-review

122 Scopus Citations


The degradation rate plays an important role in predicting and assessing the long-term energy generation of photovoltaics (PV) systems. Many methods have been proposed for extracting the degradation rate from operational data of PV systems, but most of the published approaches are susceptible to bias due to inverter clipping, module soiling, temporary outages, seasonality, and sensor degradation. In this paper, we propose a methodology for determining PV degradation leveraging available modeled clear-sky irradiance data rather than site sensor data, and a robust year-over-year rate calculation. We show the method to provide reliable degradation rate estimates even in the case of sensor drift, data shifts, and soiling. Compared with alternate methods, we demonstrate that the proposed method delivers the lowest uncertainty in degradation rate estimates for a fleet of 486 PV systems.

Original languageAmerican English
Pages (from-to)525-531
Number of pages7
JournalIEEE Journal of Photovoltaics
Issue number2
StatePublished - Mar 2018

Bibliographical note

Publisher Copyright:
© 2017 IEEE.

NREL Publication Number

  • NREL/JA-5J00-67945


  • Degradation rates
  • durability
  • photovoltaic (PV) field performance
  • PV lifetime
  • reliability


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