Bad (2000) proposed a method to determine the optimum slope angle and orientation of solar collectors for different periods of operation (1-365 days) at any position in the Malaysian territory. He mentioned that the optimum slope angle as well as the orientation can be found conveniently and accurately by this method. Later on he applied this method to calculate the optimum tilt angle over Thailand and Philippines. The present comments are focused on these statements and the novelty of this work. (C) 2016 Elsevier Ltd. All rights reserved.