We summarize the concept for ex-ante cost estimations for sanitation systems based on mass flows as developed within a Master thesis by Verena Germann in the framework of the GRASP project ([Generation and Assessment of Sanitation Systems for Strategic Planning](https://www.eawag.ch/en/department/sww/projects/grasp-generation-assessment-of-sanitation-systems-for-strategic-planning/)) by Dorothee Spuhler . The supporting information contains some illustrative examples for cost calculations for a set of sanitation systems for different areas in Arba Minch, a small town in Ethiopia.