The paper presents a numerical tool named Shared Simulation Environment (SSE) developed at the University of Pisa within the Clean Sky GRA AEA European project. This tool aims at the dynamic simulation of the electrical energy absorption of the various on-board systems during the manoeuvres of the new all-electric Green Regional Aircraft (GRA). In the GRA an appropriate management of the electrical power available aboard is required to avoid generator overloads or temporary lack of energy for powering safety-critical systems. The SSE is developed in order to permit the design and the validation of the electrical Energy Management Logics under development within the project. The paper describes the sharing of the activities between the partners of the project and the methodologies used to develop the SSE by integrating models coming from different simulation environments (Simulink, AMESim, Dymola). It also depicts the architecture of the first prototype of the SSE implemented at the University of Pisa, and describes the effects on the computation time of different integration methods, together with some preliminary simulation results.