The folowing master thesis has focused on the optimisation and analysis of fixed mounting systems for solar parks. It has been done in colaboration with Hilti Corp., one of the most important designers and producers of fixed mounting systems for solar power farms worldwide. The current paper compares two existing Hilti's fixed mounting systems each of them made of different material. This comparison shows the differences between two products with the same flexibility, ease of mounting and design concept but made of different materials and produced through different manufacturing processes. At the same time, the analysis aims not to only compare but also to find the optimum utilization point for both systems, in terms of span and cost. The span, or the distance between two support structures determines significantly the output cost of the system overal. As a result the "optimum span" has been also a target of the study. Al the results found have been based on a cost model designed within Hilti specialy for this report which embraces, concurrently, al load data calculated by other Hilti software and other hot topics with regards to design. Although plenty of load calculations and redesigning have been done the ultimate tool used has been the mentioned cost model. This powerful tool has permitted the comparison of both fixed mounting systems in terms of costs, performance and optimisation. Nevertheless, the three concepts just mentioned are aforementioned and they can be described using a performance ratio given by the cost model. This ratio which relates the system cost with the power output from the instalation and has been used as the main assessment variable is Euro/Wp. Thus, a comparison valid not only in the engineering field but also in the marketing can be obtained from the model drawing conclusion whether it is better to design a fixed mounting system for solar parks in aluminium or steel and what are their optimum utilisation points.