This paper presents a model of overnight development costs for offshore wind projects and tests for the presence of economies of scale and learning effects. Both industry-wide and country-specific learning effects are analyzed. Recently, "pilot projects" have been proposed in states such as Maine and New Jersey with the hope of inducing cost savings in future larger utility scale projects. Therefore the impact of country-specific learning effects are of particular importance. The dataset used in the analysis consists of forty-one European offshore wind projects. Research findings do not suggest that the costs exhibit economies of scale, nor do we find robust evidence of either industry-wide or country-specific learning effects. (C) 2015 Elsevier Ltd. All rights reserved.