Capítulos en libros The restructuring process that took place in the Spanish electricity market in 1998 has caused the appearance of new procedures and rules, and the implementation of decentralized operation models. Under this new competitive framework, utilities pursue supply strategies to maximize their benefits. This paper proposes a stochastic building model of competitive supply curves under uncertainty, whose objective is to maximize the expected profit of a generation utility in the day-ahead market of a deregulated electrical system. The model contemplates the global strategy of the utility, but also it specifies the bid for each generation unit. At the same time the model has a great flexibility characterizing different market conditions. Firstly, the formulation and the restrictions of the iterative optimization problem are described. Afterwards, a brief review of the model algorithm, based on successive optimizations for different scenarios, is showed. Next the building up procedure of the bidding supply curves is explained. Finally, a case study is presented that allows to check the validity of the proposed model. info:eu-repo/semantics/publishedVersion