As states across the country struggle to increase local development of renewable energy, policymakers are turning to innovative program designs to meet their renewable electricity targets. Massachusetts recently adopted a unique, auction-based price support mechanism for the solar portion of its renewable portfolio standard. During the program development process, the Massachusetts Department of Energy Resources (DOER) used system dynamics to simulate potential solar renewable energy certificate market conditions under the proposed regulations. The modeling exercise resulted in several program design changes that will lead to a more stable certificate market. System dynamics can be a useful tool for developing and improving sustainability programs.