Electric lighting is responsible for up to one third of an office building’s electricity needs. Making daylight more available in office buildings can not only contribute to significant energy savings but also enhance the occupants’ performance and wellbeing. Anidolic Daylighting Systems (ADS) are one type of very effective façade-integrated daylighting systems. All south-facing office rooms within the LESO solar experimental building in Lausanne (Switzerland) are equipped with a special type of ADS. A recent study has shown that these offices’ occupants are highly satisfied with their lighting environment. The most energy-efficient south-facing offices have a lighting power density of less than 5 W/m². The lighting situation within these “best-practice”-offices has been assessed using the RELUX Vision lighting software. Because this lighting situation is very much appreciated by the occupants, it was used as a starting point for developing a yet more energy-efficient office lighting design. Two new lighting designs, leading to lighting power densities of 4 W/m² and 3.1 W/m² respectively, have been suggested and simulated with RELUX Vision. Simulation results have shown that the performance of these new systems can be expected to be comparable to that of the current lighting installation within the “best-practice”-offices or even better.