In this work, we intend to evaluate the triangular sustainability of not-for-profit organizations, putting a special emphasis on the study of economies of scale. After a collection of raw data from the historical archives of the institution (a 'Santa Casa da Misericordia de Barcelos'), we constructed a panel database. Using this database, we estimated cobb-douglas costs functions, by applying fixed and random effects. We found that Portuguese institutions as the one here studied (belonging to the Portuguese Social Economy and as a representative of the Holy Houses of Mercy) exhibit economies of scale, which ask for a renewed perspective of the sector by the regulating entities.