Archimedes screw generators are a small-scale, eco-friendly hydropower technology. Despite their promise as a sustainable energy technology, the design specifics of the technology are not well documented in the published literature. Existing performance prediction models often fail to accurately forecast power loss, particularly as it relates to the outlet of the screw generator. To address this, a comprehensive computational fluid dynamic model was developed and evaluated using both laboratory-scale experiments and real-world data. This yielded an extensive dataset that covered wide variations in design parameters. The dataset was then used to inform the development and evaluation of an outlet power loss prediction model. The resulting model significantly improved the accuracy of overall performance predictions, reducing average error to 13.68 % compared with nominal experimental data – a substantial improvement over previous models, which averaged around 42.55 % error for the same test cases. Notably, the new model achieved an absolute error of 5 % or less in over 26 % of comparison points, marking a remarkable advancement by predicting outlet power loss by more than 28.8 %.