With the U.S. federal government having yet to pass significant renewable energy legislation in the face of growing climate change concerns, it has been left to the states to encourage renewable energy expansion through renewable portfolio standards (RPS) and other means. Renewable portfolio standards are designed to guarantee that a certain percentage of a state’s total energy output comes from renewable energy sources. As of 2016, 30 states have a RPS. This paper explores the causes behind state adoption of RPS by conducting a multivariate analysis of social factors such as education level, political factors such as Democratic control of the state legislature, economic factors such as unemployment rate and diffusive determinants. The results of this analysis are applied to contribute to a greater understanding of issues surrounding renewable energy policy adoption at the state level.