Our lifestyle largely depends on the availability of energy. But we need to convert and manage energy respecting the environment and limiting the ecological impact. Therefore, we have in front of us two main challenges. How can we provide the rising amount of energy demanded, in order to maintain the current standard of living in the developed countries and to allow developing countries to enhance their life style? How can we manage this growing energy consumption without damaging the environment and without altering the climate? In order to ensure the EU commitments on the Kyoto Protocol, on 29th January 2008 the European Commission launched the Covenant of Mayors (CoM), an initiative aimed to a unilateral and voluntary participation of European cities in the energy efficiency improvement, in the renewable energy sources use increasing and in the greenhouse gas emissions reduction within 2020. The Covenant of Mayors is the mainstream European movement involving local and regional authorities, indifferently from the dimension/size of the city, with the aim of reducing CO2 emissions through a customized approach to specific territorial conditions, in this way addressing to the municipal level all those policies finalized to manage and reduce the greenhouse gas emissions, especially by means of a governance tool represented by the Sustainable Energy Action Plan (SEAP). Starting from the analysis of the Baseline Emission Inventory (BEI), identifying the principal energy consumptions and CO2 emissions in a reference year as a sort of a picture of the energy “status quo”, local authorities can list priority actions and initiatives to be implemented in the Sustainable Energy Action Plan in order to achieve the goals of GHG mitigation, in the sectors of Buildings, Lighting, Heating/cooling, Electricity production, Cogeneration/Trigeneration, District Heating/cooling, Renewable Energy Sources, Transport & Mobility, Energy planning, Participation and awareness creation.