Encouraging voluntary government action via a solar-friendly designation program to promote solar energy in the United States.

SignificanceDue to market and system failures, policies and programs at the local level are needed to accelerate the renewable energy transition. A voluntary environmental program (VEP), such as SolSmart, can encourage local governments to adopt solar-friendly best practices. Unlike previous research, this study uses a national sample, more recent data, and a matched control group for difference-in-differences estimation to quantify the causal impact of a VEP in the public, rather than private, sector. We offer empirical evidence that SolSmart increased installed solar capacity and, with less statistical significance, the number of solar installations. The results inform the design of sustainability-focused VEPs and future research to understand the causal pathways between local governments' voluntary actions and solar market development.