Energy Transitions in Regulated Markets

Natural gas has replaced coal as the dominant fuel for U.S. electricity generation. However, U.S. states that regulate electric utilities have retired coal more slowly than others. We build a structural model of rate-of-return regulation during an energy transition where utilities face tradeoffs between lowering costs and maintaining coal capacity. We find that the current regulatory structure retires only 45% as much coal capacity as a cost minimizer. A regulated utility facing a carbon tax does not lower carbon emissions immediately but retires coal similarly to the social planner. Alternative regulations with faster transitions clash with affordability and reliability goals.