To achieve the energy sector's decarbonization targets, the BIG4HEAT project models and evaluates the performance of horizontal underground storage, a promising solution for limiting land use impact. It also explores the possibility of converting existing infrastructure, such as former hydrocarbon reservoirs, into inter-seasonal or seasonal storage units. The effect of the geographical position of the storage facility within the network is analyzed in order to optimize its hydraulic and energy integration. Finally, the project identifies the operational risks associated with each configuration and proposes strategies to ensure the reliability and efficiency of the system, as well as a simulation of the return on investment (ROI) of the various solutions, taking into account future needs and possibilities for expansion.