Abstract This paper focus on the determination of the influence of the electrode-surface area / anode-compartment volume ratio (ESAVR) on the performance of microbial fuel cells (MFC), both in terms of the generation of electricity and the removal of organic matter from waste. Real wastewater coming from a winery factory was used and five ESAVRs were tested in separate MFCs, ranging from 0.15 to 0.75cm2cm-3. Results demonstrate that the electricity generation increases by decreasing the anode-compartment volume. Thus, by increasing ESAVR, maximum current density increased from 583 to 2416 mA m-2. However, the COD removal was found to be more efficient upon decreasing the ESAVR (from 590 to 1075 mg COD L-1 d-1). Results are of extreme significance for the mechanical design of MFC in order to optimize their performance during normal operation.