Advanced oxidation processes (AOPs) are gaining attention in sewage treatment as a further cleaning step for the elimination of persistent organic substances. Three designed laboratory-scale AOP reactors are presented and their energetic consumption when treating indigo carmine as a test organic compound is assessed. A photolytic (UV/H2O2) and a photo-Fenton reactor with one ultraviolet and three fluorescent lamps, respectively, and an electrolytic system consisting of a boron-doped diamond electrode were built. When considering total energy consumption, substantial differences arose due to the stirring devices.