Energy infrastructures have been under pressure by a series of demands and responsibilities to solve crucial problems, both present and future, such as climate change and distributive justice. In this article I argue that, to harmonise many of these issues, a better understanding must be reached of the relationship between users and infrastructure. To this end, I maintain that infrastructure studies, in combination with user analyses from Social Studies of Science, Technology and Society (STS), can significantly contribute to this task. In this way, from a genealogical perspective and through the analysis of archival documents from the Public Administration of Chile, I analyse the case of the colgados: a group of electrical energy users without a contractual relationship with the distribution companies, which emerged as a problem during the 1980s when the electrical infrastructure began to be privatised during the military dictatorship. Analysis of the case of the colgados shows that, despite evidence presented in studies commissioned to learn about the profile of this group of users, those in charge of the infrastructure at the time – businessmen, economists, and politicians – interpreted the results of these studies within the economic-rational framework with which public policies were designed as of that time in Chile. Thus, this case study serves as an example of the obduracy with which assumptions of economic-rationality are applied. Strikingly, despite the evident contradiction between user behaviour and the assumptions under which public policies operated, the illusion of economic-rationality as the most representative explanation of user behaviour continues to be the central focus of infrastructural relationships in the present, whose most common device is the electricity tariff.