We present in this paper GRENAD, a Multi-Agent System based framework for the simulation and piloting of power-grids and particularly smart grids. Exploiting a component-based approach, it allows a flexible design of complex smart grid applications by providing a generic canvas where extensible, modular and reusable components, defined on the basis of their functionalities, can be easily combined and connected. Thanks to Multi-Agent approach, a set of such components can naturally be integrated into a coherent economical agent. GRENAD makes no assumption on the energy definition and eases the development of MAS control algorithms for smart grids. The level of details of the energy-related information is controllable. This information is computed either through internal physical models or by interfacing with external simulators. We present here our model, illustrate its features with a rich example which exhibits its genericity, and demonstrate how a coordination protocol can easily be integrated to it.