Particle accelerators are the drivers for large-scale research infrastructures for particle physics but also for many branches of condensed matter research. The types of accelerator-driven research infrastructures include particle colliders, neutron, muon or neutrino sources, synchrotron light sources and free-electron lasers, as well as medical applications. These facilities are often large and complex and have a significant carbon footprint, both in construction and operation. In all facilities grid power is converted to beam power and ultimately to the desired type of radiation for research. The energy efficiency of this conversion process can be optimized using efficient technologies, but also with optimal concepts for entire facilities.