The world is facing a change in the regulatory framework for converting non-electrical energy into electrical energy from new renewable energy sources that are affordable and environmentally friendly. The greatest need type of energy in current life and in the future is electrical energy. The SDGs (Sustainable Development Goals) program number seven emphasizes affordable and clean energy. The development of science and technology, especially in the field of power electronics and the NRE (New Renewable Energy) multi-source electrical energy storage system are sought to be able to meet energy needs in the supply and storage of future sustainable electrical energy. Each type of application of NRE conversion itself has a fluctuating nature in the supply of electrical energy produced. The prototype of the NRE interface system that has been realized in previous studies then requires a mathematical modeling of the system. This aims to produce optimal settings of the control process, so that the system is able to provide appropriate and sustainable electrical energy. Mathematical modeling analysis of the system gives the optimal and sustainable energy availability equation for the multi-source NRE, which basically fluctuates.