Electrochromic properties of poly(aniline N-butylsulfonate)s (PANBUS) coatings on indium-tin oxide (ITO) glasses exposed to an ion conducting polymer films were investigated. The ion conducting polymer films were prepared via photocross-linking reactions of methoxy polyethylene glycol-mono methacrylate with tri(propylene glycol) diacrylate in the presence of a photoinitiator and LiClO4. Mechanical properties of the electrolyte film were enhanced by introducing styrene or butylmethacrylate into the polymer network. Color contrast and optical response of the PANEUS-based window were improved by adding Nafion into the electrolyte. The electrochromic (EC) window assembled with PANBUS, Nafion containing polymer electrolyte film, and tungsten trioxide coated ITO glass (type 2) required less energy for operation (+/- 1.5 V) compared to the EC window without tungsten trioxide film (type 1, +/- 2.0 V). By applying +/- 1.5 V, optical density of the type 2 window changed from zero to maximum of 1.2, corresponding transmission change of higher than 95%. Lifetime tests show that the type 2 window could support more than 2.3 x 10(3) cycles, of 60 s duration.