The advanced oxidation processes (AOPs) UV/H2O2, UV/O3 and O3/H2O2 were optimised to achieve a 90% degradation of the micropollutant atrazine in continuous-flow reactors. The experiments were performed with spiked Berlin tap-water. The comparison of mechanistically different oxidation systems needs a non-specific figure-of-merit to avoid influences by system-inherent parameters. The chosen figure-of-merit consists of the electrical energy per order of magnitude in oxidation per m3, EE/o. The combination O3/H2O2 proved to be the most efficient process by means of energy consumption.