This research examines the impact of accuracy in tidal current energy resource assessment on the likely economics of a tidal array project, ultimately estimating the impact of resource uncertainty on overall lifetime project economics. The analysis utilises field data gathered at 3 key locations at the European Marine Energy Centre (EMEC) tidal test-site in the Fall of Warness, Orkney. Data analysis techniques appropriate for application to tidal current energy projects are presented and the results obtained interpreted. The widely adopted Matlab code t_tide is then used to conduct harmonic analysis of the tidal current velocity data records. The adjacent ADCP records enable analysis of the spatial variability of the tidal resource at the EMEC site. Electricity generation potential and project revenue estimates are generated using simple and clear assumptions regarding typical tidal turbine topology and array layout. The impact of resource uncertainty on the prediction of Annual Energy Production (AEP) of the idealised array is calculated by varying the temporal and spatial resolution of the ADCP data utilised as input to the analysis, and similarly by using various lengths of the measured tidal records. These scenario based predictions are analysed in a simple financial model to examine the effect resource estimate uncertainty has on the projected returns on investment. Overall, the results suggest one clear conclusion: the range of impacts on project economics of uncertainties introduced by the resource estimation process warrant greater investment of time and money by project and technology developers at an early stage of development.