The effect of molar concentration of aqueous electrolytes on the capacitance characteristics of supercapacitors (SC), in which amorphous carbon or carbon nanotubes are used as electrode materials, is studied. Aqueous solutions of sulfuric acid with concentrations of 1–6 M are used as the electrolytes. It is shown that the specific capacitance of SC depends significantly on the concentration of the electrolyte, properties of the electrode material, and the methods of treatment of carbon materials for enhancing their wettability with aqueous electrolytes.