Why do some cities adopt more renewable energy than others? This mixed methods study quantifies the effect that a supportive city mayor can have on his/her city's renewable energy transition. We draw on the case of sizable cities (at least 30,000 residents) in the US states of Massachusetts and the Japanese prefecture of Chiba. We catalogue instances of mayoral support for renewables and specific companies over the last ten years drawing from online newspapers and government documents, statistical modeling, and case studies of key mayors. Mayoral support to renewable power greatly improve solar adoption, but the strength of grassroots social capital in these cities can strengthen or shackle mayors' efforts, depending on the type of social capital. By highlighting the role of mayors in renewable energy, we hope to clarify in what situations mayors can make a difference in helping cities transition to renewable energy.

为什么有些城市比其他城市采用更多的可再生能源？这项混合方法研究量化了支持城市的市长对其城市可再生能源转型的影响。我们借鉴了美国马萨诸塞州和日本千叶县的大城市（至少 30,000 名居民）的案例。我们根据在线报纸和政府文件、统计模型和主要市长的案例研究，对过去十年中市长对可再生能源和特定公司的支持实例进行分类。市长对可再生能源的支持极大地提高了太阳能的采用率，但这些城市的基层社会资本实力可能会加强或束缚市长的努力，具体取决于社会资本的类型。通过强调市长在可再生能源中的作用，