Due to the large environmental impact of the electric energy sector, evaluating the policy instruments employed in this arena is a particularly pressing issue. In the United States, state policy is a major driver of sustainable energy development and provides a unique opportunity to conduct comparative policy research. Thirty-two states have implemented a renewable portfolio standard (RPS), a policy instrument that mandates renewable resource use. Although similar on the surface, these policies present staggering variation in the design elements they incorporate. This dissertation investigates patterns of policy design, scope and outcomes of RPS, contributing to the literature on policy design and effectiveness, and expanding the empirical knowledge of state sustainable energy policies. The first essay presents an in-depth state-by-state analysis of RPS design elements, complemented by the development of a policy classification scheme. Examining RPS design under the angle of stringency of goals, discretion in means, and strength of the enforcement regime introduces a measure of comparability. It highlights that a rigid focus on singular measures of policy strength and broad policy types detracts from understanding the impact of individual design features. The second essay underlines this argument, relating RPS design characteristics quantitatively to policy response. The results show that both more stringent goals and, to some extent, increased discretion in means are associated with higher policy response. The research design used is innovative, in that it accounts for the full complexity of RPS, while measuring outcomes at the level the policy targets (retail sales). The final essay concentrates on a single design attribute, policy scope. Focusing on a sector currently excluded from most state sustainable energy policies - consumer-owned utilities - it assesses future policy scenarios for their inclusion. To remediate the complete lack of emissions data on consumer-owned utilities, it develops for the first time a method to estimate the carbon intensity of electricity sales from this sector. Based on these estimates, future carbon management scenarios are developed for the inclusion of consumer-owned utilities in renewable policies, including interaction with energy efficiency policies.