Technologies are generally described for a capacitor device that includes parallel nanotubes. Such a capacitor device may include two parallel electrodes, each of which includes an array of nanotubes that extends from the surface of the respective electrode towards the other electrode. The nanotubes can be substantially parallel to each other and substantially perpendicular to the electrode from which they extend. The space between the electrodes and the nanotubes can be filled with an electrolyte or dielectric material, for example, a solution of an electrolyte solute in a suitable solvent. Such a capacitor device can have high electrode surface area but can avoid pore effects, in comparison to high surface area porous electrodes which do not have interpenetrating electrodes.