Energy forms and their extensive scale are remarkably significant for the ways that societies are organized. This article shows the importance of how societies are ‘energized’ and especially the global growth of ‘fossil fuel societies’. Much social thought remains oblivious to the energy revolution realized over the past two to three centuries which set the ‘West’ onto a distinct trajectory. Energy is troubling for social thought because different energy systems with their ‘lock-ins’ are not subject to simple human intervention and control. Analyses are provided here of different fossil fuel societies, of coal and oil, with the latter enabling the liquid, mobilized 20th century. Consideration is paid to the possibilities of reducing fossil fuel dependence but it is shown how unlikely such a ‘powering down’ will be. The author demonstrates how energy is a massive problem for social theory and for 21st-century societies. Developing post-carbon theory and especially practice is far away but is especially urgent.