In the context of climate protection policies, this article addresses the post-carbon transitions driven by a few cities. It investigates the political dimension and multilevel character of these transitions: political, because they gain initial impetus from environmentalist associations, are maintained over time by uncommon political will and give rise to politically divergent transition paths; multilevel, because the upsurge of local climate policies results from the alliance between transnational municipal networks, international institutions and cities, with cross-influences between these levels. Additionally, the analysis of contrasted paths towards exiting fossil fuel followed by two ‘pilot’ cities (Hanover and Växjö), the conditions of their success and limitations encountered, highlights another component of this multilevel character: the weight of national or federal support for local climate action and of influence between political actions performed at different levels, which appear to broaden the scope of urban energy transitions.