<p>The day-ahead electricity market is crucial for improving energy generation and sales planning. This paper evaluates a hydrothermal network-constrained unit commitment model and its solution method developed for the Mexican electricity market. The objective function maximizes the economic surplus for market participants. The problem is formulated as a mixed-integer nonlinear programming problem, considering real-world constraints and a nonlinear hydropower generator function. A decomposition approach is employed to solve the problem. Additionally, a new component has been introduced to handle the nonlinear aspects of the hydropower generator function using a first-order Taylor’s approximation. Empirical results are presented, including the solution of a representative case from Mexico’s electricity market, illustrating its practical application. This novel method can be valuable in markets with substantial hydropower resources, improving the accuracy and timeliness of system operation scheduling.</p>