In one embodiment of the invention, a method of forming an energy storage device is described in which a porous structure of an electrically conductive substrate is measured in-situ while being electrochemically etched in an electrochemical etching bath until a predetermined value is obtained, at which point the electrically conductive substrate may be removed from the electrochemical etching bath. In another embodiment, a method of forming an energy storage device is described in which an electrically conductive porous structure is measured to determine the energy storage capacity of the electrically conductive porous structure. The energy storage capacity of the electrically conductive porous structure is then reduced until a predetermined energy storage capacity value is obtained.