A Solar Panel is a technology that can harness the energy of the sun. Solar energy is one of the only two known sources of energy in the world of Code Geass with the other being Sakuradite. Whereas Sakuradite is shown that it can power things like cars or Knightmare Frames, solar energy can power the entire city. Solar Panels appear as early as the first episode powering the Britannian occupied city of Tokyo. In Code Geass: Akito the Exiled, the Europia United, along with Britannia, have solar panels powering their cities. Whether or not other countries have this technology is currently unknown.