In solar water splitting, efforts in scaling up the photoelectrochemical cell beyond laboratory scale have started to attract significant attention. Several large-area devices have been demonstrated, but typically the efficiencies are much lower than their small-area equivalent. Here, two-dimensional finite element modeling is used to evaluate the different sources of voltage loss specifically related to scale-up in solar water splitting devices operated in neutral pH solutions. We quantitatively investigate the influence of the electrode area to these scale-up associated losses (substrate ohmic loss, electrolyte ohmic loss, and local pH-gradient related losses). About 600 mV additional overpotential is needed due to these losses for a cell with electrodes of height of 8 cm at a current density of 10 mA cm(-2). We show, however, that by applying engineering and cell design strategies, the voltage losses can be mitigated, resulting in an acceptable similar to 50 mV overpotential. Overall, this study highlights the additional challenges to be considered in photoelectrochemical cell scale-up and provides strategies to manage and mitigate scaling-related losses.