Microbial electrochemical technologies (METs) and especially microbial fuel cells (MFCs) are considered to allow energy harvest from the fuel wastewater during its treatment. However, the majority of studies use either "artificial" wastewater, amended wastewater, (i.e. with addition of chemicals), or pre-enriched microbial anodes. As these strategies might not be transferable to large scale, this study uses exclusively amendment free municipal wastewater as inoculum and sole carbon and energy source. It is shown that electrons can be harvested, at maximum current densities of 0.01 mA cm(-2). In weeldy cycles using batch systems (with 90 cm(2) L-1 anode surface) only a minor fraction (<10%) of the available charge from COD removal was turned into electricity by a highly diverse anodic microbial community. This performance is below those achieved by pre-enriched anodes or in amended wastewater studies, illustrating the need for more fundamental, application relevant studies. (C) 2017 Elsevier B.V. All rights reserved.