Superconducting magnets in particle accelerators can store energy without loss. They serve to keep the accelerated charged particles in a circular orbit. After a few hours of operation, the magnetic fields are lowered. Conventional particle accelerators then lose the stored energy. But, for a future circular collider, the FCC collaboration is developing technologies to harvest this energy, the amount of which could be comparable to the annual consumption of a small town. This same technology could also be used to minimise losses – which cost a few billion euros per year – in current electricity networks.