Deployment of renewable energy has increased in the power sector due to declining costs and policy instruments that have supported these technologies at state and federal levels. Half of the 29 states with renewable portfolio standards will have met their requirements by 2021. Higher level mandates are currently being set or considered by many states. Implications on power sector capacity mixes, economic and environmental outcomes, and potential policy alternatives need to be evaluated for better decision making and resource planning. With higher levels of renewables, the uncertainty around technological progress, the evolving policy landscape, fuel markets, and availability of complementary technologies (e.g., energy storage and transmission) need to be addressed.