The focus of this special issue is on the energy transformations taking place in several European countries (Austria, Belgium, Germany, and Switzerland) and at the federal and subnational (state) levels in the United States with special attention given to California. The cases examined all have federalist structures, and with the exception of the federal level of the United States, all have relatively ambitious climate and renewable energy targets. We compare these states out of an interest in better understanding how federalism interacts with energy transitions. The comparison is also intriguing as at the federal level the United States presents a stark contrast with the federalist European countries considered in this special issue but at the subnational level many similarities can be found.