An energy-exergy study of the geothermal fluid network in the area of Larderello-Valle Secolo-Farinello (Tuscany, Italy), which is currently undergoing modernization and replacement, is described. This study was carried out by setting up a simulation code, which is able to simulate the entire transportation network beginning with the geothermal wells (with relative connections) through the power plants up to the re-injection of the condensed water in the reservoir. In this way, the entire geothermal system can be considered as a semi-closed cycle. The results presented have been obtained by simulating the part of the network built so far (Larderello-Valle Secolo). The study of the entire network, including the Farinello area, will be possible when the transportation and distribution network has been completed. In order to outline the global exergy performance of the system, a study was made of the Larderello and Valle Secolo power stations (running at the present time) with attention paid to the elements that cause the main exergetic losses.