This study provides an updated analysis of long-term energy system scenarios for California consistent with the State meeting its 2050 climate goal, including detailed analysis and assessment of electricity system build-out, operation, and costs across the Western Electricity Coordinating Council (WECC) region. Four key elements are found to be critical for the State to achieve its 2050 goal of 80 percent greenhouse (GHG) reductions from the 1990 level: aggressive energy efficiency; clean electricity; widespread electrification of passenger vehicles, building heating, and industry heating; and large-scale production of low-carbon footprint biofuels to largely replace petroleum-based liquid fuels. The approach taken here is that technically achievable energy efficiency measures are assumed to be achieved by 2050 and aggregated with the other key elements mentioned above to estimate resultant emissions in 2050. The energy and non-energy sectors are each assumed to have the objective of meeting an 80 percent reduction from their respective 1990 GHG levels for the purposes of analysis. A different partitioning of energy and non-energy sector GHG greenhouse reductions is allowed if emission reductions in one sector are more economic or technically achievable than in the other. Similarly, within the energy or non-energy sectors, greater or less than 80 percent reduction from 1990 is allowed for sub-sectors within the energy or non-energy sectors as long as the overall target is achieved. Overall emissions for the key economy-wide scenarios are considered in this report. All scenarios are compliant or nearly compliant with the 2050 goal. This finding suggests that multiple technical pathways exist to achieve the target with aggressive policy support and continued technology development of largely existing technologies.