Cities play increasingly recognised roles in global climate change responses: as change laboratories, spaces of opportunity, and as administrative and economic hubs that concentrate human and financial resources and needs. They host high climate mitigation potential and acute climate adaptation vulnerabilities. Scholarship flags conventional urban planning approaches to limit global warming to 1.5°C as inadequate. Yet urban sustainability transitions literature features few examples of functioning alternative governance and planning paradigms. This paper assesses one such approach, new municipalism: social movements centred on a democratic transformation of the local economy and state. We combine attention to urban sustainability transitions and new municipalism research to interrogate whether and how the latter can facilitate the provision of leadership and institutional arrangements that enable urban transformation to sustainability. Our desk study considers two prominent examples of new municipalism in Spain, where Barcelona en Comú and Ahora Madrid arose as anti-austerity movements to combat neoliberal urban agendas during the 2010s. We find that the praxis of collective decision-making associated with new municipalism does offer inclusive, innovative policy pathways and the potential to implement experimental knowledge and learning in complex real-world settings at the urban scale. We argue, however, that powerful neoliberal mechanisms impose structural constraints on the very push for deep political change that new municipalist movements embody. By linking transformative climate governance needs with new municipalism movements and wider political economic structuring forces, we explicate the tensions and contested dynamics of institutionalising progressive social movements in the multi-scalar governance of urban sustainability transformation.

Energy infrastructures co-evolve with and are enacted and acted upon by not only technical but also regulatory and institutional factors, as well as sociocultural contexts. As solar energy plants require access to land and the electric grid, the recent uptick in solar energy infrastructure features interplay with local specificities. This article thus examines the uptake of solar energy in Portugal at both the national and local scales. The purpose is to contribute to a timely debate on critical renewabilities and to provide valuable insights for the future rollout of solar photovoltaic (PV) capacity in Portugal. The study demonstrates that solar energy policy measures not only show some start-stop aspects of the utility-scale solar PV roll-out, but have also tended to favour large companies, rather than community or individual operators. Three case studies point to a range of public attitudes regarding solar PV roll-out and its underlying drivers that are locally influenced by land use and sociocultural contexts, apparently more so than by concerns of low-carbon energy transitions. A key point for future solar energy transitions is, therefore, that local communities’ concerns should be understood and approached cross-sectorally. Furthermore, the intersection of energy transitions and justice must be considered from a multi-scalar, multi-sited and cross-sectoral perspective.