The present work is a Master semester project created collaterally to the mechanical engineering major (SGM) at the Swiss federal institute of technology (EPFL). The project aim is the comprehension, assessment and optimization of an HVAC energy system which is located on a cruise ship. To approach the subject, a first analysis of the real field data from the ship is made. Then, an approximation of the energy demand of the HVAC ystem on board is carried out using Matlab. The real consumed HVAC energy is compared with the theoretical results. Based on these results, optimization options regarding the HVAC systems and their possible implementation are discussed.