As electric systems transition toward deep decarbonization, there is a growing need to understand how reliability risks evolve, particularly as grids become more weather-sensitive and increasingly reliant on variable renewable generation. This study examines how different decarbonization pathways can shape system reliability using EPRI’s US-REGEN capacity expansion (CE) and detailed hourly operations modeling framework.
By evaluating system performance across multiple weather years (WY), the analysis captures the impacts of renewable variability and regional resource conditions on flexibility needs, including the roles of energy storage, gas combustion turbines (CTs), transmission, and electrolytic hydrogen production. Results show that weather-year variability is a major driver of system performance, influencing renewable output and the deployment and operation of balancing resources. Scenario comparisons reveal shifts in the mix of renewables, energy storage, and firm capacity, while regional analyses highlight differences in transmission flows, seasonal peak demands, gas deliverability requirements, and hydrogen production patterns.