It has been reported that arm trajectories for reaching movements are not planned so as to minimize the energy cost. However, from a biological point of view, saving energy consumption would be important for survival. If human brains do not apply the criterion of the minimum energy consumption to reaching movements, what is the reason? If they do, what has been unrecognized in the studies of the minimum energy model? In this study, we computed energy costs required for the reaching movements planned by the minimum energy cost model and the minimum endpoint variance model which is one of the leading models for reaching movements, respectively. In the computation we considered corrective sub-movements to compensate for the positional error due to signal-dependent noise for motor commands. The results show that the trajectories planned so as to minimize energy cost without considering the effect of noise are easily affected by noise. Therefore, when noise is large, sub-movements are required to reach the target and as a result the total energy cost becomes larger than that for the minimum endpoint variance model. These results suggest that the human arm reaching movement might be optimized on the energy cost and we should consider the effect of the noise in the analysis of the reaching movement from the view point of optimization on the energy cost.