The focus of the Energy Management sub-programme is on the optimization of the management of distribution networks in presence of Distributed Energy Resources (DER) and load control with an energy and market perspective. Technical and economic scenarios will be considered for the active distribution network development, taking into account the most important smart grids features, i.e., resilience to generation and load variability, demand response, energy balance optimisation, grid loss reduction and optimal asset management. Specific attention will be given to all ICT implications. The main aim of this report “D2.1 – Overview of Simulation Tools for Smart Grids” is to provide an overview of the different simulation tools available, i.e. developed and in use, at the different research centres. Required new tool capabilities are identified and extensions to the existing packages are indicated. An analysis of the emerging power systems challenges together with a review of the main topics regarding smart grids is provided in Chapter 1. The requirements for the simulation tools and the list of available tools in the different research centres and their main characteristic are reported in Chapter 2. The main aspects of the different tools and their purpose of analysis are listed in Chapter 3 along with the main topics concerning the new requirements for tools in order to allow a proper study in the smart grid context. Gaps capabilities and model consolidation of the analysed tools are reported in Chapter 4. A bibliography is provided in Chapter 5. A comprehensive comparative table is reported at the end of the report in the Annex. An analysis of each tool is provided as well.