Decarbonization policies and technological change have increased expectations that future power sector resource portfolios will be characterized by significant deployment of wind and solar, retirement of traditional dispatchable resources, and changing hourly load profiles from end-use electrification. The objective of this research is to explore approaches for assessing potential reliability concerns associated with these power sector trends. The analysis uses EPRI’s U.S. Economy, Greenhouse Gas, and Energy (REGEN) model and a newly developed post-processing tool to provide additional perspectives on reliability impacts of decarbonization scenarios using existing power system reliability metrics. Illustrative analysis using the post-processing tool indicates that assumptions about the availability of import capacities from neighboring systems materially influence regional reliability assessments. The evolving supply-side mix, especially the growth of wind and solar, and load profiles from electrification alter seasonal and daily reliability risks. The analysis suggests areas for future research to connect long-term planning models with more granular resource adequacy and reliability tools.