This paper analyses sustainability transitions in the electricity system, using recent theories on socio-technical pathways. The paper describes three possible transition pathways and indicates the implications for (grid) infrastructures. The 'transformation pathway' is characterised by a further hybridization of the infrastructure; in the 'reconfiguration pathway', internationalisation and scale increase in renewable generation lead to the emergence of a 'Supergrid'. The 'de-alignment and re-alignment pathway' is dominated by distributed generation and a focus on more local infrastructures. We suggest that this pathway, which involves a major restructuring of the electricity system, is less likely than the other two. The de-alignment and re-alignment pathway is therefore more dependent on external developments and/or strong policy interventions. All pathways, however, require major investments in infrastructure and innovative technologies. © 2010 Elsevier Inc.