Tidal Energy Conversion farms are a promising but not yet mature technology whose costs are still highly uncertain. In order to be able to predict costs for early Technology Readiness Level (TRL) phases, this paper presents a cost model in which a detailed parametrization of all Capital Expenditures and Operation and Maintenance items has been carried out, whose results make it possible to select the best design alternative in each case. Each parameter has been updated with numerical values based on both actual and foreseen costs. A generalist tool that integrates all these parameters and that calculates, among other variables, the Levelized Cost of Energy (LCOE) has also been developed. This tool, in which the parameters have been updated, has been applied as a case study to a single-rotor GESMEY-designed generator in the case of both fixed and controllable pitch; the numerical results for the operation parameters selected are also included. The model presented in this paper is proposed in order to compare different design alternatives, under user-defined operation conditions, for tidal energy projects in early TRL phases and the effect on their LCOE.