This presentation summarizes research examining the economic and engineering challenges of flexible operations of power generation assets from large-scale renewable deployment. This work uses a novel platform for linking electric sector investments and detailed market operations in EPRI’s US-REGEN computer simulation modeling framework. Focusing on California and Texas, model results estimate the economic value of intermittent electric generation capacity and illustrate how these evaluations depend on the level of renewable energy deployment, regional resource endowments, generation fleet flexibility, assumptions about regional electricity trade, and storage. These scenario comparisons elucidate shared challenges and best practices while systematically quantifying the relative importance of factors influencing large-scale renewable integration.