For tidal stream energy to become a fully-fledged renewable energy source, a complete understanding of the tidal stream resource characterisation is required. For this purpose, the International Electrotechnical Commission (IEC) has elaborated a technical specification for the assessment of the tidal stream resource, “IEC-TS 62600-201: Marine energy—Wave, tidal and other water current converters—Part 201: Tidal energy resource assessment and characterisation” (IEC-62600-201), which presents a wide set of recommendations with the aim of standardising tidal stream resource characterisation. The IEC-62600-201 divides resource assessments into two different classes: feasibility and layout design. The model implementation (mesh resolution, boundary conditions) and the effort required in terms of computational time varies significantly from one class to another. For these reasons, the objective of the present work is to explore the IEC-62600-201 using the Orkney Region (N Scotland) as a case study. Over-all, it was found that the IEC-62600-201 works well, offering a detailed characterisation of the resource; however, in order to make the IEC-62600-201 more manageable some aspects such as the grid resolution requirements and the TEC modelling should be revisited for future editions.