Supporting solar power in renewables portfolio standards: Experience from the United States

Renewables portfolio standards (RPS) have become an increasingly popular option for encouraging the deployment of renewable electricity. It is a relatively new policy mechanism, however, and experience with its use is only beginning to emerge. One key concern is whether RPS policies offer adequate support to a wide range of renewable energy technologies and applications or whether, alternatively, they will favor a small number of the currently least-cost forms of renewable energy. This article documents the design of and early experience with state-level RPS programs in the United States that have been specifically tailored to encourage a wider diversity of renewable energy technologies, and solar energy in particular. As shown here, state-level RPS programs specifically designed to support solar have already proven to be an important driver for solar energy deployment, and those impacts are projected to build in the coming years. State experience in supporting solar energy with RPS programs is mixed, however, and full compliance with existing requirements has not been achieved. The comparative experiences described herein highlight the opportunities and challenges of applying an RPS to specifically support solar energy, as well as the importance of policy design details to ensuring that program goals are achieved. - Research highlights: → Many states have adopted RPS policies with solar or DG set-asides. → Solar and DG set-asides have become a significant driver for solar growth. → Compliance with solar/DG set-aside targets has been mixed. → The estimated retail rate impacts have thus far been relatively modest. → Various emerging issues will affect the future impact of RPS policies on solar growth.