As one of the ways of increasing fuel economy for full single-screwed ships, this paper presents newly developed asymmetric stern, which features that stern end before propeller is shifted from ship's center plane. Shifting distance is maximum at propeller boss around, and gradually reverts to the center as going up & downwards. The model experiments were carried out for panamax size BC with this shape and the necessary power of full scale was estimated by using newly proposed self propulsion analysis method. The results show about 7% energy saving can be expected by use of this stern.