Using structuration theory, this paper examines capital budgeting and its role in the ‘energy trilemma’. The key focus is on the role of knowledgeable agency inffq s. the analysis of strategic conduct. In particular, demonstrating how accounting tools can be used by executive managers, who whilst dominant in their own organisations, are themselves subordinate to the government in the United Kingdom and at the European level. The strategic conduct of actors is examined in a narrative, theorised case study setting, which spans across 11 years, 2006- 2017. The principal contribution to knowledge from this study is the extent to which strategic investment accounting played in changing regulatory and government policy and spending requirements in a privatised industry. The most dominant party, the government and regulators, were forced to take the generators’ concerns seriously, because the generators (based on knowledge derived from capital budgets) restricted their capital expenditure rather than mobilising their resources. The need for resources to reduce emissions provided an opportunity for the industry to force the government to consider the problem of energy. The generators highlighted that this was not only a problem of price for consumers and environmental sustainability, but as one of long term supply. The generators argued that government had to address all aspects of the trilemma when creating policy.