The most observable leakage radiation from an advanced civilization may well be from the use of power beaming to transfer energy and accelerate spacecraft. Applications suggested for power beaming involve Earth–to-space applications such as launching spacecraft to orbit, raising satellites to a higher orbit, and interplanetary concepts involving space–to–space transfers of cargo or passengers. We also quantify beam-driven launch to the outer solar system, interstellar precursors and ultimately starships. We estimate the principal observable parameters of power beaming leakage. Such beams would be visible over large interstellar distances. This implies a new approach to the SETI search: Instead of focusing on narrowband beacon transmissions generated by another civilization, look for more powerful beams with much wider bandwidth This requires a new approach for their discovery by telescopes on Earth. Further studies of power beaming applications should be done, which could broaden the parameter space of observable features we have discussed here. By observing leakage from power beams we may well find a message embedded on the beam.