Grillenberger, J. Seidel, M. JACoW Geneva, Switzerland The growing global energy consumption challenges the energy efficiency of any technology and thus also of research facilities. Many large research facilities are based on accelerators that provide a primary beam for secondary particle generation but require several MWs of power from the grid. The goal of each new generation of accelerator facilities is to achieve higher flux, rates, brightness, and luminosity which typically requires greater power. A discussion on improving the energy efficiency of existing and, in particular, future accelerators inevitably presents itself. In this paper, the energy efficiency of the cyclotron based PSI-proton accelerator facility will be discussed. It will be demonstrated that a cyclotron is the machine of choice for accelerator driven systems due to its comparatively high energy efficiency. Furthermore, it is also shown that by adopting more efficient magnet and RF technologies, an even higher energy efficiency may be achieved.