We report on the mechanism of hopping for bound excitons under an energy gradient. By means of a Monte-Carlo simulation, we show that this mechanism explains the movement of bound excitons observed experimentally. We show that the speed of the excitons decreases quickly with temperature. Thanks to an effective medium approximation, we deduce an analytical model to estimate the average speed at T = 0K. Finally, we compare our simulations results to the speed observed in bent ZnO wires and find a good agreement between theory and experiments. (C) 2014 AIP Publishing LLC.