WO3 is the most widely studied electrochromic material because of its high colouration efficiency and high cyclic stability. Use of tungsten hexachloride as precursor synthesizes the highly porous WO3 nanowire networks by hydrothermal method. Color efficiency of 120.3 cm2 C-1 during the coloration/bleaching process, high transmittance contrast(57%), and short switching time(tb=7 s, tc=21 s) can be achieved when employing WO3 nanowire networks as electrochromic devices.