Abstract: A system and method for creating capacitor-based electrical energy storage modules and electrical energy storage systems assembled therefrom. Submodules having a plurality of capacitors capable of storing electrical energy are used in different combinations to create electrical energy storage modules. Preferably, a number of submodules are placed into corresponding receptacles within an enclosure or cabinet, wherein the submodules become electrically connected. The number of submodules installed in a cabinet is determined by the power output desired, and the space constraints of the area in which the cabinet will be located. One cabinet of one or more submodules, or a plurality of interconnected cabinets of one or more submodules, may form an electrical energy storage module. The module may be designed to output either DC or AC electric power, and is preferably equipped with a power conversion system and/or communication and control electronics to control the charging and discharging thereof.