This paper explores a classic challenge in implementing sustainable development: how to build an integrated policy discourse across a complex and contested policy field. Renewable energy development in Wales has become a controversial issue over the past 10 years, and dramatically illustrates the institutional challenges of implementing sustainable development. This paper presents the initial groundwork of research, exploring, through an analysis of renewable energy policy, whether the recently devolved administration of the Welsh Assembly Government is better able to implement sustainable development policies than its predecessor, and whether the 'sustainable development' rhetoric of the devolved Assembly can be matched in practice. The paper examines the new arenas for deliberative policy making on renewable energy in Wales, and the new frameworks for policy delivery. We argue that at the heart of the new renewable energy policy debates are unresolved conflicts over core environmental values, which are being played out in the new institutional arrangements. These contested values, and the resulting diverse positions around renewable energy development, have been the focus of some recent research. However, the ways in which these value conflicts are played out within the policy-making processes and structures for the implementation of renewable energy, remain relatively unexplored. Therefore, a critical question examined in this paper is the extent to which the emerging policies and practices of the Assembly simply reproduce these unresolved tensions, or alternatively carry clear direction and commitment, and introduce new practices to resolve or manage these conflicts. The paper argues that the key future challenge is to build consensus in some form across these difficult divides, but that the task of constructing and institutionalising a new policy discourse of sustainable development, in the face of deep-seated and unresolved conflicts, is not yet guaranteed by the new institutional arrangements in Wales.