This study is aimed to identify the optimum parameters affecting the energy and exergy efficiencies for a novel design solar air heater (SAH) using the grey relational analysis (GRA). The effect of the different obstacle distances (L), obstacle relief angles (alpha) and Reynolds number (Re) on the energy and exergy efficiencies of the SAH is investigated. Experiments designed using L-9 orthogonal array and optimized using GRA is carried out to determine the optimal design factor levels as the lowest L and alpha and the highest Re. The parameter contrubition ratios are performed by using ANOVA analysis. Regression analysis (RA) is developed to predict the energy and exergy efficiencies. The confirmation experimental results showed that the data obtained with RA are compatible with the data obtained from experiments. (C) 2017 Elsevier Ltd. All rights reserved.