Granular material is dehumidified by: a) providing a number of dry air generators inside hoppers containing granular material; b) for each dry air generator, evaluating the dry air flow generable and/or higher energy efficiency functioning time; c) calculating the dry air flow rate for each single hopper depending on the characteristics of the granular material; and d) activating a number of generators sufficient to deliver a total dry air flow rate equal to the sum of the flow rates required by the hoppers. The number of the generators and the generators to be activated are chosen depending on the flow rate deliverable by each and/or by their respective ranges of functioning at higher energy efficiency according to an energy saving logic. The remaining generators are deactivated.