Self-consumption of renewable energies is defined as electricity that is produced from renewable energy sources, not injected to the distribution or transmission grid or instantaneously withdrawn from the grid and consumed by the owner of the power production unit or by associates directly contracted to the producer. Designing solutions in favor of self-consumption for small industries or city districts is challenging. It consists in designing an energy production system made of solar panels, wind turbines, batteries that fit the annual weather prediction and the industrial or human activity. In this context, this paper reports the context of this business domain, its challenges, and the application of modeling that leads to a solution. Through this article, we highlight the essentials of a domain specific modeling language designed to let domain experts run their own simulations, we compare with existing practices that exist in such a company and we discuss the benefits and the limits of the use of modeling in such context.