The main concern in path planning has been the time history of position, velocity, and acceleration of the end effector of the manipulator. In this study as a trajectory for the tip of the robot arm, sinusoidal path (SP) is assumed in cartesian coordinates. It is also assumed that the end point of the robot arm travels on this trajectory with the simple harmonic time function. Taking the amplitude of sinusoidal motion as a variable, an amplitude for SP motion is searched that makes the energy consumption minimum. Computations have shown that SP outward from the body of the manipulator in the xy plane and SP downward in the xy plane complete the task with the minimum energy.