The European Commission has developed a long-term strategy to obtain a highly energy performance of buildings and a reduction of greenhouse gas emissions, in order to achieve the ambitious goals of a sustainable and carbon-neutral Europe. Buildings are responsible for approximately 40% of energy consumption and 36% of CO2 emissions in the EU. Recognizing this significant impact, improving the energy efficiency of buildings has become a crucial aspect of the EU's endeavors to achieve the target of at least 60% emission reductions by 2030 in the building sector in comparison to 2015 and achieve climate neutrality by 2050. This thesis fits into this context, considering the energy-plant retrofit of a non-residential office building, with the purpose of examining the impact of Building Automation and Control (BAC) systems on energy savings, showcasing how Building Management System can effectively optimize heating, cooling, ventilation and air conditioning systems, lighting, and other building components.