Due to the continuous growth in the utilization of the evaporative coolers in the buildings, power reduction is a crucial demanding in this sector. For this purpose, the minimization of the pressure drop (which is proportional to power consumption) shall be considered in the pre-design of the indirect evaporative cooling systems. Therefore, in this study, using analytical solution of the pressure drop for two groups of fin heights (10, 15 and 20 mm in the dry and 5, 10 and 15 mm in the wet channel), the variations in pressure drop, power consumption and wet-bulb effectiveness of an indirect evaporative cooler are evaluated. The predicted results showed that for both of the channels (dry and wet), the pressure drop and required fan power of the system increase as the fin height decreases. Based on the numerical simulations (considering hydrophilic porous layer treatment in the wet channel), the total power consumption increases from about 100-130 and 196% as the fin height (in the dry channel) decreases from 20 to 15 and 20-10 mm. In addition, the product air temperature decreases with the decrease in the fin height and increases with the increase in the volume flow rate. (C) 2017 Elsevier B.V. All rights reserved.