This report presents the results of a study of a 50% renewables portfolio standard (RPS) in California in 2030. The study was funded by the Los Angeles Department of Water and Power (LADWP), Pacific Gas and Electric Company (PG&E), the Sacramento Municipal Utilities District (SMUD), San Diego Gas & Electric Company (SDG&E), and Southern California Edison Company (SCE), (“the utilities”) to examine the operational challenges and potential consequences of meeting a higher RPS. This study was conducted by Energy and Environmental Economics (E3), with assistance from ECCO International. A companion study was conducted by DMV KEMA examining “smart grid” technologies that may become available to help alleviate challenges associated with high penetration of distributed generation. An independent advisory panel of experts from industry, government and academia was commissioned to review the reasonableness of the assumptions and to provide input on the study. The California Independent System Operator (CAISO) also provided input on key study assumptions.