Environmental threats of: [Climate changes, Green House gasses (GHG) emissions, and Economic crisis] led to paradigm shift towards renewable clean Energy, which becomes a major strategy. Egypt taking steps by raising its potentials of Renewable energies production from (2%) in 2010 aiming to be (53%) of electricity from Renewables by 2035, basically depends on development in Solar Energy. Photovoltaics (PV) applications become a major approach for Solar Energy utilization on: (buildings “Rooftop” and Façades) through two major systems: [Building Applied Photovoltaics (BAPV), and Building Integrated Photovoltaics (BIPV)]. Applications of (PV) in buildings have great double impacts; Active: of Clean Energy production, and Passive: duo to shading, thermal Insulation and time lag effects. Research aims to Optimize (PV) applications on: [“Rooftop” and Façades] to get visible Efficient Operation according to parameters: [Tilt angel – Orientation – Type of applications], thus to propose a reliable Matrix, that can help: [Architects– (PV) Developers] in decision making of the most Prior of (PV) applications. Depending on Research Methodology, and by aid of reliable (IT) Simulation tools used (“PVSYST” – “Energy +”), then Validated Results by records of Experimental (PV) Station, found that; Optimizing the application of (PV) Panels on standard educational building “Rooftop”; can save more than (37 %) of conventional annual Energy consumptions. Otherwise, optimizing the whole application of (PV) Panels on both:[“Rooftop” and (South, East, and West facades respectively)] can save more than (81%) of “Base-Case” Energy consumptions, which approaches to be a Zero Net Energy educational Building (ZNB), by clear energy source.