This work describes a mathematical model for determining the power demand for a vertical shaft mowing machine, particularly taking into account the influence of speed on cutting power, which is different from that of other models of mowers. The influence of the apparatus’ rotation and translation speeds was simulated in determining power demand. The results showed that no changes in cutting power were produced by varying the knives’ angular speed (if translation speed was constant), while cutting power became increased if translation speed was increased. Variations in angular speed, however, influenced other parameters determining total power demand. Determining this vertical shaft mower’s cutting pattern led to obtaining good crop stubble quality at the mower’s lower rotation speed, hence reducing total energy requirements.