This chapter addresses new territory for political ecologists: the politics of energy systems. It brings concepts from thermodynamics and systems ecology into dialogue with the history of electrification to make a case for a historically grounded political ecology. The chapter centres on the assumption that fossil fuels must be substituted for an equal amount of renewable energy sources to withstand climate change and peak oil. But this conjecture is misleading. By examining the turbulent histories of electrification in the USA, the Soviet Union and the former Third World – notably in India and Cuba – it is argued that electricity systems are fundamentally historical products that represent political and economic rationales. Energy, in turn, behaves in specific ways depending on the energy system’s geographical outlay – an outlay contingent on the interests manifest in the system. The centralized long-distance transmission grids that are prevalent in the world today demand high energy input; yet this energy demand is not linked to the technology ‘itself’ but to the interests it represents. To ask how we are to replace fossilized energy potential with renewable neglects this political ecology of the energy system. Instead the interests embodied in energy systems can be challenged to achieve a low-carbon transformation. The chapter ends with suggestions for future research into the remarkably underexplored political ecology of energy systems.