Electrical power from the fuel cells is converted and controlled by power electronics that are composed of control units, converters and switching devices. During the power management, the inevitable power losses induce heat generation in the power electronics. In this, effective design for the cooling system is essential in terms of safety, reliability, and durability. A liquid cooling system for the power electronics is applied to chill the electrical components below the thermal specifications. Nonetheless, the layout of cooling components is usually designed after the completion of the chassis and power electronics in the automotive applications, thus, only a little freedom is allowed to change the layout. Thus, it is significant and urgent to investigate the cooling performance before finalizing the layout design. In this paper, one dimensional and computerized fluid dynamics code is employed to simulate the performance of the cooling system at the early stage of conceptual design. Three different layouts of cooling systems are chosen to compare the ensuing systematic cooling performances. The liquid flow rates, pressure drops, and maximum temperatures are computed by the numerical simulations of the cooling system which comprises the cold plates, liquid pump, radiator, and plumbing network. It is demonstrated that for a fuel cell electric vehicle of 100 kW, the dual cooling loops with a specified array control the maximum temperatures below thermal specification by inducing the higher liquid flow rate of rate of 33.4 L/min through radiator than 20.0 L/min in a single loop. The proposed systematic numerical simulation provides significant information to determine the layout of the power electronics coupled with the cooling performance at the early stage of conceptual design. (C) 2014 Elsevier Ltd. All rights reserved.