Windows are the single greatest source of energy waste within most commercial and residential buildings. Our diffusely reflective electrochromic thin film will reduce air conditioner usage and related CO emissions by -35%. Unlike most other smart window technologies, our electrochromic window film is completely user controllable. On sunny warm weather days, it can be switched to reflective mode to significantly reduce solar heating through windows and dramatically reduce air conditioner usage. During cold weather days, it can be switched to transparent mode, allowing solar heating to assist with interior warming, therefore reducing heating system usage.