Semi-transparent photovoltaic (STPV) windows will increase the surface area which can generate useful electricity in buildings whilst still providing natural illumination to the users inside. A further benefit is that buildings will require less cooling in hotter months since they will reflect the infra red part of the suns radiation. State of the art STPV windows have a light to electric power conversion efficiency of ˜ 6% whilst allowing less than 20% of the daylight to pass through with reduced blue and green colour resulting in a sepia tinged light. We propose to move beyond the state of the art by covering the surface of the window with narrow stripes of solar cells below the eye’s resolution. This will lead to a natural daylight spectrum on the inside and the ability to use solar cells with high power conversion efficiency. Furthermore, this approach allows to select the solar cell coverage to match to match geographically varying sun light conditions. If the project is entirely successful we predict a power conversion efficiency of 10%, at the same time allowing 50% of the visible light to pass.