An all-solid monolithic electrochromic (EC) system, based on tungsten oxide and vanadium pentoxide, was fabricated and tested for electrochromic performance. The system exhibits a solar transmittance modulation between around 58 and 9% and visible transmittance modulation between around 65 and 13% in the bleached and coloured states, respectively. The system was coloured and bleached for over 2000 cycles. The EC performance of the system has also been carried out under different external conditions. The possibility of the addition of an improved Li ion conductor and a protective layer is also studied. These changes seem to render the EC system more stable and faster in EC response. The results of these studies indicate a good potential of such a monolithic system for smart window application.