Abstract: A solar panel for use in a roof mounted array of solar panels, each panel having ridges protruding outwardly and adjacent to the side edges for receiving a standing seam cap between side-adjacent panels. Each solar panel is formed as an integral structure having a photovoltaic module an edge of which is sealed by a base substrate. The base substrate is configured to have lipped top and bottom edges which interlock to form a watertight seal between top-adjacent and bottom-adjacent solar panels. The solar panel array can be mounted on a roof, in place of shingles or the like, to provide environmental protection for the interior of a building.