Daylighting can offer the benefit of view comfort and saving energy, so it has become more and more important in acting as the principal source of lighting in buildings. This study attempts to evaluate energy saving potential of the well-known MonodraughtTM sunpipes installed in a supermarket in the UK. A lighting analysis software package RELUX is used as the simulation tool to calculate daylight factor and illuminance distribution within the supermarket. The energy saving potential of using MonodraughtTM sunpipes in the supermarket is assessed using RELUX Energy. The simulation results indicate that a considerable saving in the lighting-related energy consumption could be achieved through use of MonodraughtTM sunpipes accompanied by an artificial lighting control.