The development of alternative energy solutions to meet the increasing energy demand requires the expansion of the production network. In this context hydropower plants (HPPs) represent a reliable renewable energy source [3] and the possibility of integrating a pumping storage system makes HPPs an excellent way to stock energy. Besides energy generation, hydropower plants present numerous benefits, including flood control and water supply, leisure and storage of electricity [7]. Nevertheless in the recent years some criticism was raised against megaprojects and few studies pointed out that budgets are constantly exceeded and schedules overrun. The methodology proposed by Gomez and Probst [4] is hereafter used allowing to study the hydropower cost evaluation as a complex problem and to reveal the key factors that have a strong influence. The purpose is to identify the processes which leads to an increase of the final cost of large dam project. Results clearly showed the involvement of uncontrollable factors in the process. The reasoning leads to a final statement: the human impossibility to foresee the unpredictable does not justify the criticism and the prejudice that was risen against hydropower plants, whose benefits remain undeniable.