Workshop on the energy efficiency of proton driver accelerators High power proton drivers are needed to generate secondary particles at high intensities, such as neutrons, muons or neutrinos. The applications of these facilities have a broad spectrum in the fields of particle physics and condensed matter physics. On the other hand, the production of megawatt-class proton beams implies the consumption of large amounts of electrical energy. This aspect is seen more and more critical in the public society and in funding agencies. New projects and operating facilities must focus on improving the energy efficiency with a higher priority. With this workshop we are aiming to supporting such developments towards higher efficiency. The anticipated needs of secondary particle flux for experimental applications will be reviewed, as well as intrinsic efficiency aspects of different accelerator concepts, suited for high power beam production. The main goal of this workshop is to consider the whole power conversion chain from grid to the secondary radiation needed at the experiments. In addition, we will look at important auxiliary systems of proton drivers, such as cryogenic facilities. A short summary report will be prepared with recommendations on efficient technologies and future R&D on this aspect of high intensity proton driver accelerators. The workshop will be supported by the EUCARD-2 program, particularly the work package EnEfficient.