This study attempted to evaluate the environmental impact and energy benefit of offshore wind power systems using life cycle assessment (LCA) and net energy analysis. The environmental impact of offshore wind power systems is based primarily on ferrous metal, which is used to install the foundations, towers, and nacelles. The impact categories with the greatest relevance were fossil fuels and respiratory inorganics. This study assumed that the life cycle of an offshore wind power system has four stages (production, installation, operation and maintenance, and end-of-life). Two scenarios were examined in this study. The major difference between the scenarios was that Scenario 2 included an offshore substation. The overall environmental impact in Scenario 2 was higher than that in Scenario 1 by approximately 10%. The net energy analysis in this study included the evaluations of cumulative energy demand (CED), energy return on investment (EROI), and energy payback time (EPT). For Scenarios 1 and 2, CED was 0.192 and 0.216 MJ/kWh, EROI was 18.7 and 16.7, and EPT was 12.8 and 14.4 months, respectively. Moreover, when the recycling of waste materials was considered, each scenario produced a 25% lower environmental impact, 30% lower energy requirement, and 4 months lower EPT. (C) 2016 Elsevier Ltd. All rights reserved.