Rethinking Capacity Accreditation in High-Renewable Power Systems: Discrepancies, Drivers, and Practical Insights from a CAISO Case Study

The global transition toward decarbonized power systems has fundamentally altered the resource adequacy landscape, shifting the focus from peak gross load to “net load” profiles where risk is concentrated during early evening periods of diminished solar output. High penetrations of variable energy resources and battery storage create complex interactions that cause capacity accreditation methodologies to diverge, challenging the ability of simplified deterministic proxies to ensure long-term reliability. This paper deconstructs six accreditation methods—categorized into deterministic, performance-based, and probabilistic frameworks— to identify the technical drivers behind divergent resource valuations. Utilizing the California