The aim of this paper is to develop a methodology to determine the economic feasibility of a floating offshore wind farm. The methodology proposed considers that the life-cycle cost of a floating offshore wind farm is composed of the costs of each of the phases of its life-cycle (concept and definition, design and development, manufacturing, installation, exploitation and dismantling). Moreover, they are subdivided considering their sub-costs and taking into account the five components of a floating offshore wind farm: offshore wind turbine, floating platform, mooring, anchoring and electric system. The method ends when the economic feasibility indexes are calculated. The methodology has been used to analyse an offshore location: the Galician region (North-West of Spain). Results indicate that the best economic area in the Galician region is the area located from the Ria de Pontevedra to the Ria de Ribadeo. In addition, comparing the three floating offshore wind platforms, the semisubmersible platform and the spar platform are the best options in economic terms. The method proposed can be used to determine the economic keys in order to develop a floating offshore wind farm in any location. (C) 2016 Elsevier Ltd. All rights reserved.