This paper presents the results from a case study on the role in policymaking of UK Energy Sector Indicators (ESIs), introduced by the government in 2003. The findings show that the ESIs constituted a very minor element within the broader evidence-base used by policymakers, and that this indicator set and their objectives were poorly known even to central players in the sector. The findings of this research provide further evidence for the observation that scientific knowledge (including evaluations, assessments and indicators) seldom play an instrumental role in policymaking, and are more likely to produce indirect, conceptual and political impacts. The analysis provides a number of tentative conclusions concerning such potential indirect impacts that accrue mainly through processes of dialogue and argumentation both during the preparation of the indicators and after their publication as part of the annual reporting by the UK energy department. The ESIs have played various conceptual and political roles, yet the concrete outcomes in terms of policy change remain to be explored. The conclusions highlight the limitations of rationalist notions of direct, instrumental use in the efforts to understand the role of indicators in policymaking. The paper concludes by three tentative propositions concerning the explanations to the absence of instrumental role of the ESIs, which could be usefully explored in future research: the characteristics of the energy sector; the characteristics of the UK policy culture; and the exceptionality of the ESIs in the general evidence-base of UK energy sector.