An highly porous electrically conducting film that includes a plurality of carbon nanotubes, nanowires or a combination of both. The highly porous electrically conducting film exhibits an electrical resistivity of less than 0.1 Ω·cm at 25 C and a density of between 0.05 and 0.70 g/cm3. The film can exhibit a density between 0.50 and 0.85 g/cm3 and an electrical resistivity of less than 6×10−3 Ω·cm at 25 C. Also included is a method of forming these highly porous electrically conducting films by forming a composite film using carbon nanotubes or nanowires and sacrificial nanoparticles or microparticles. At least a portion of the nanoparticles or microparticles are then removed from the composite film to form the highly porous electrically conducting film.