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Photovoltaic Module Soiling Map

NREL scientists and engineers have generated a map that highlights soiling parameters of fielded photovoltaic panels at more than 80 locations—either soiling stations or photovoltaic sites—across the United States.

Last Update: Oct. 11, 2017 

SRatio Range

Map Content

The map shows locations of PV systems ( markers) or soiling stations ( markers). Click on each site for:

  • Years of operation
  • County where the site is located (Note: Specific locations are not given because of contractual agreements.)
  • Soiling Ratio (SRatio): insolation-weighted mean of the daily ratios between the output of soiled and cleaned PV devices
  • SRatio uncertainty
  • Soiling Rate (SRate): median of the daily rates of change in soiling ratio during dry periods
  • SRate range: the 97.5th and the 2.5th percentiles of the soiling rate distribution.


The soiling parameters in the map were generated using the following methodology:

  • Soiling Ratios, Rates, and Uncertainties for photovoltaic sites were extracted according to the method proposed in:
    M. Deceglie, L. Micheli, and M. Muller, "Quantifying Soiling Loss Directly from PV Yield," IEEE Journal of Photovoltaics (accepted).

  • Soiling Ratios for soiling stations were calculated as described in:
    L. Micheli and M. Muller, "An Investigation of the Key Parameters for Predicting PV Soiling Losses," Progress in Photovoltaics: Research and Applications 25 (2017) 291–307. 

  • Soiling Rates for soiling stations were calculated as described in:
    M. Deceglie, M. Muller, Z. Defreitas, and S. Kurtz, "A Scalable Method for Extracting Soiling Rates from PV Production Data," in 2016 IEEE 43rd Photovoltaic Specialists Conference, Portland, Oregon, 2016.

  • Uncertainty in the soiling station SRatio was calculated using the method proposed in:
    M. Muller, L. Micheli, and A.A. Martinez-Morales, "A Method To Extract Soiling Loss Data from Soiling Stations with Imperfect Cleaning Schedules," in 2017 IEEE 44th Photovoltaic Specialists Conference, Washington, D.C., 2017. 

    The irradiance for each location has been sourced from National Solar Radiation Database.

Michael Deceglie

Researcher IV, Physics