We demonstrate that the experimentally obtained photocurrent density (mA/cm(2)) of a WO3 based photoelectrochemical cell decreases as a function of increasing photoactive area. This trend is predominantly caused by a non-linear decrease in resistance of the interface between the conducting FTO electrode and the photoactive material (WO3), as determined by electrochemical impedance spectroscopy. In agreement with this observation is that the relatively high interfacial resistance of large area electrodes can be reduced by introduction of conductive layers, as is evident from improved photocurrents obtained for relatively large, graphitized C-70 modified WO3 photo-electrodes. (C) 2015 The Electrochemical Society.