The biophysical foundations of socio-economic systems are underrepresented in the vast majority of macroeconomic models. This lack is particularly troublesome when considering the links between energy, matter and the economy in the context of the energy transition. As a remedy, we present here a biophysical stock-flow consistent macroeconomic model calibrated at the global scale, that combines detailed bottom-up estimates for the high capital intensity of renewable energies and the decreasing energy return on investment (EROI) of fossil fuels. We find that the completion of a global energy transition scenario compatible with the 1.5 °C objective of the Paris Agreement leads to a decrease of the system’s EROI and to high investment share, employment and inflation trends, characteristic of a “war economy”. Our results further indicate that a slower growth rate eases the transition, and call for further work on post-growth scenarios studies.