The project team representing Gazi University Faculty of Engineering Department of Mechanical Engineering, M. Zeki YILMAZOGLU (graduate level), Yusuf YABIR, Ahmet ORHAN (undergraduate level) and Project Supervisor Assist. Prof. Ibrahim ATILGAN acquired the second prize, together with Istanbul Technical University, at the "Universities Project Contest on Energy Efficiency Design and Application of Central Air-Conditioning Systems" which is organized by HSK firm. Totally 29 universities applied and 20 of them could submit their final reports to the contest. There was no first prize given in this contest, where Yildiz Technical University acquired the third prize. Other universites were rewarded with mensions. In our winning project, applications of energy efficiency at central air-conditioning systems is focused. Mechanical system plumbing, optimum system selection and alternatives of energy efficiency are compared together with their economical analyses for a shopping-center which is to be built in Kayseri. Frequency invertors and VAV systems are controlled in design. Additionally, natural cooling application and optimum vent location are considered. Also, building automations systems and energy efficient mechanical installation are inspected. The results of the aconomical analyses indicate that the feedback time of this processes is 6 months, with the application of the planned alternatives under the climate conditions of Kayseri city.