The effect of different structural designs on the performance of electrical double layer capacitors (EDLCs) has been studied through a mathematical model that considers the mass transfer and conservation of charge equations. The structural design parameters considered in this study are the electrode thickness, electrode porosity, and initial electrolyte concentration. The performance parameters studied are the cell capacitance, specific energy, specific power, and electrolyte concentration for a range of discharge rates. The results of this study can be used to optimize EDLCs at various operating conditions.