Resource assessment is an important phase of tidal energy projects. Extensive literature is nowadays available on this topic with most studies focussing on the time-scales of the tide or the spring-neap cycle. The evolution of the resource over longer time scales has yet received very little attention in the scientific literature. In the present contribution, we investigate the effect of the 18.6 year lunar nodal cycle on the depth-averaged current of the Alderney Race (France). Firstly, we identify the major constituents of the study zone with the UTide Matlab functions. Two datasets are used: a 36.5 day time-series of depth-averaged current and elevations acquired in the Alderney Race and a 24 year times-series of tidal heights acquired in a neighbouring harbour. The analysis shows that the tide is mostly controlled by the semi-diurnal constituents M2, S2 and N2. Secondly, we verify the ability of UTide functions to predict the changes in amplitude of the major components over decadal time-scale. Thirdly, we predict the tidal resource of the Alderney Race over the period 2014 – 2034 and analyse the yearly changes within this period. The results show that the change of resource is of the order of +/-10% and that the next decade (2020–2029) will be characterised by a significant reduction of the resource.