The paper presents the investigation of the optimum design parameters of a solar air heater (SAH) having wire ribs as artificial roughness by using the Taguchi method. The solar air heater has arc shape roughness geometry with apex upstream flow on the absorber plate. The objective of this paper is to obtain a set of parameters that deliver maximum thermo-hydraulic performance. For this objective, a new parameter the thermo-hydraulic improvement parameter ( ^ηTHIP), has been introduced. For the present analysis, the effects of Reynolds number (Re), relative roughness pitch ( P/e), angle of attack ( α), and relative roughness height ( e/Dh), denoted by A, B, C, and D, respectively, have been considered. An ( L ₁₈ = 6 ¹ · 3 ²) orthogonal array (OA) was chosen as an experimental plan for applying the Taguchi method. The set of control factors for the solar air heater SAH which delivers the maximum Nusselt number (Nu), and minimum friction factor ( fr) – are A ₆B ₂C ₂, and A ₁B ₁C ₃ respectively. To obtain the maximum THIP the experimental set-up requires only one single run using the parameter A ₆B ₂C ₂, hence there is no need to run it all 54 times.