Transition to a sustainable energy regime is one of the key global societal challenges for the coming decades. Many technological innovations are in the pipeline, but an uncritical appraisal of anything and everything called green innovation lacks methods for testing both the necessity and the sufficiency of these developments. We propose to develop a philosophy of energy to fill this lacuna. Its task is to explore and clarify the space in which the so-called energy transition is taking place. This article sketches the fundaments of such a philosophy and suggests how it might be built upon the work of twentieth century critics of the functioning of energy in society, including Mumford, Bataille, and Heidegger; but not without empirical analysis of contemporary energy systems. Via the example of flux and potentiality - two apparently opposing conceptions of energy - we propose that a philosophy of energy allows for a broader perspective on specific problems in energy transition, and illuminates implicit and problematic assumptions behind these problems. Keywords : Philosophy of energy; Energy transition; Sustainability; Renewable energy; Mumford; Bataille; Heidegger.