Energy Recovery is at the threshold of becoming a key means for the advancement of accelerators. Recycling the kinetic energy of a used beam for accelerating a newly injected beam, i.e. reducing the power consumption, utilising the high injector brightness and dumping at injection energy: these are the key elements of a novel accelerator concept, invented half a century ago. The potential of this technique may be compared with the finest innovations of accelerator technology such as by Wider��e, Lawrence, Veksler, Kerst, van der Meer and others during the past century. Innovations of such depth are rare, and their impact is only approximately predictable. The panel notes with much interest that the ERL technology is close to high-current and high-energy application, requiring dedicated and coordinated R&D efforts, with the stunning potential to revolutionise particle, nuclear and applied physics, as well as key industry areas. This comes at a time where attention to sustainability is an overarching necessity for this planet, not least big science. ERLs are therefore primed for inclusion among the grand visions our field has been generating. Adequate support for the development, in Europe and worldwide, will allow this potential to be realised. CERN Yellow Reports: Monographs, Vol. 1 (2022): European Strategy for Particle Physics - Accelerator R&D Roadmap
