The paper explores the role of natural resource accounting and calculations as tools for inducing movement towards ecologically sound policy making. We draw from the theoretical debates in social studies of science and technology (STS) to understand how calculations gain their power in real-world decision-making. Through in-depth case analysis of a local energy production decision in Finland, we study how and under what conditions calculative methods related to environmental valuation affect the rationalities applied in policy decisions. On the basis of our analysis, we claim that new calculative rationalities do not become significant through changing ways of thinking alone. There is a need for shift of calculative framing. This shift requires active promotion by powerful actors and furthermore, new framings need to become embedded in the rules of the game of decision making. Our analysis suggests that the methods of STS can provide a valuable tool for economists’ creation of richer understanding of the dynamics between calculative rationalities and the institutions of decision-making. In-depth case analysis of decision making involving the use of natural resources brings out the multitude of ways in which calculations can take part in or be excluded from the making of natural resource policy.