A growing body of literature has emerged that examines cities as key sites for socio-technical experimentation with a variety of initiatives and interventions to reduce carbon emissions, upgrade ageing infrastructure networks and stimulate economic development. Yet while there has been a wide survey of global initiatives and attempts to explain the wider processes driving such experimentation (Bulkeley and Castán Broto, 2013) there remains a lack of empirical case study analysis to bring the concepts into context. In this paper we use the concept of urban experimentation as a lens to discuss the political and social ramifications of one such intervention in a city’s energy infrastructure network, with an examination of the Pecan Street smart grid project in Austin, Texas. The ability for cities to manage socio-technical transitions and their inflections by specific locales has been largely neglected in social science research, yet cities around the world are facing similar problems of ageing infrastructures, pressures of resource consumption and demanding shifts towards intermittent renewable technologies. We argue that cities are key arenas for the trialling, testing and development of smart products that can help transition towards a low-carbon economy, however the ‘opening up’ of cities as experimental nodes is contributing to a restructuring in socio-technical urban governance, creating new spaces for private investment while delegating responsibilities for carbon control down to urban citizens.