Comparison of Capacity Value Methods for Photovoltaics in the Western United States

Research output: NRELTechnical Report


This report compares different capacity value estimation techniques applied to solar photovoltaics (PV). It compares more robust data and computationally intense reliability-based capacity valuation techniques to simpler approximation techniques at 14 different locations in the western United States. The capacity values at these locations are computed while holding the underlying power systemcharacteristics fixed. This allows the effect of differences in solar availability patterns on the capacity value of PV to be directly ascertained, without differences in the power system confounding the results. Finally, it examines the effects of different PV configurations, including varying the orientation of a fixed-axis system and installing single- and double-axis tracking systems, on thecapacity value. The capacity value estimations are done over an eight-year running from 1998 to 2005, and both long-term average capacity values and interannual capacity value differences (due to interannual differences in solar resource availability) are estimated. Overall, under the assumptions used in the analysis, we find that some approximation techniques can yield similar results toreliability-based methods such as effective load carrying capability.
Original languageAmerican English
Number of pages38
StatePublished - 2012

NREL Publication Number

  • NREL/TP-6A20-54704


  • approximation methods
  • capacity value
  • Garver's approximation method
  • photovoltaics
  • PV
  • reliability-based method
  • Z method


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