Scalable Complex Orders: How Euphemia Algorithm Improved Scalability while Facilitating Participants Bidding

Abstract

Euphemia is the algorithm used in the Single Day-Ahead Coupling (SDAC) to clear the European Day-Ahead Market. Scalable Complex Orders (SCOs) were introduced in 2025 to represent generation units fixed costs and technical minima, while improving the scalability of the clearing process. To quantify the impact of SCOs, we analyze one month of data from the Iberian market and simulate three counterfactual scenarios in which SCOs are replaced by other available order types.We then compare these scenarios with the historical market outcome. Results indicate that SCOs help units recover fixed costs and respect the technical minimum, while substantially reducing the algorithm running time.