Energy performance upgrade of stadiums constitutes a complex and demanding task because of both the size and the variety of the involved energy loads. The present article aims to summarize the basic results of the implemented study on the energy performance upgrade of the Pancretan Stadium, Crete, Greece. This target was approached with a cluster of passive and active measures: replacement of old openings, a photovoltaic station, an open loop geothermal system, installation of energy-efficient lighting devices, a solar-biomass combi system and a Building Energy Management System (BEMS) for the control of the main energy consumptions. The dimensioning of all the proposed active systems is optimized through the computational simulation of their annual operation. With the applied technologies, the achieved annual energy saving percentage exceeds 83%. The Renewable Energy Sources annual penetration percentage is calculated at 82% versus the annual energy consumption. The Stadium’s energy performance is upgraded from rank D to rank A+, according to the European Union’s directives. The set-up cost of the under consideration energy performance upgrade systems is approximately calculated at 2,700,000 €, with a payback period of 12 years, calculated versus the achieved monetary savings due to the reduction of the consumed energy resources.