In this thesis a plant area within an oil refinery is analyzed energetically with the scope to improve the energy efficiency of that area. The Fluid Catalytic Cracking Unit (FCC) is examined, which has the purpose to convert long hydrocarbon chains into shorter ones through cracking. This is done with the help of a catalyst. During the cracking process coke on the catalyst is produced as a reaction product. This coke is burned within the plant generating most of the energy required for the process. The base for the analysis is the key performance indicator called Energy Intensity Index® (EII®), which makes it possible to compare the energy consumption of oil refineries all over the world. As a first step all factors influencing the EII® are identified and examined. This results in two essential approaches to improve the FCC from an energy perspective. One of the approaches is to analyze, scrutinize and improve the needed calculations to determine the amount of coke burned. Therefore, in this thesis the calculation of the coke balance at the site is compared with two external calculation methods. The second approach aims to improve the heat integration of the product streams with the aim to reduce the consumption of cooling water and process steam. In a preliminary step, a cooling water and steam balance is compiled for the FCC. Based on these results, a pinch analysis is performed for selected product streams with the aim of utilizing the available energy potentials in the streams. To perform the pinch analysis the freeware tool FI2EPI is used. For the identified new process design it is necessary to install new heat exchangers. These are dimensioned via Excel and the results are presented in the form of heat exchanger data sheets. The impact of the improved heat integration on the EII® is then evaluated and examined. The results of this work provide a basis for the management of the petroleum refinery to reduce the EII® and consequently the energy consumption by suggestions to improve the heat integration and the calculation of the coke balance.