Based on the simulation equations, which were developed earlier (Rao, 1999 and Rao et al., 2007) relating the oxygen transfer coefficient k (= K_La₂₀ (?ľ/g²)^1/3) with theoretical power per unit volume of water X (= N³D²/g^4/3?ľ^1/3) and k with actual powerconsumed by the surface aerators per unit volume PV (= P/(V??(g?ľ)^_1/3), methodology has been demonstrated to the save the energy consumption, defined by ?? (=P_V /k), where K_La₂₀ is the overall oxygen transfer coefficient at 20oC, ?ľ is kinematic viscosity of the water, N is the speed of the rotor, D is the diameter of the rotor, P is the input power available to the rotor, V is the volume of water and ?? is the specific weight of the water. Present works demonstrate that while aerating a given volume of water at constant rotor speed to achieve a desired oxygen transfer coefficient (k) in square tank surface aerator, it is always economical to use a single tank rather than using a multiple numbers of smaller tanks.