Post-subsidy offshore wind: Environmental and economic efficiency trade-offs from 93 farms in China

Global warming has spurred offshore wind development, yet subsidy phase-out in China demands efficiency improvements. We applied the Super-SBM-GML model and SHAP analysis to assess 93 Chinese offshore wind farms from 2021 to 2024. Multidimensional efficiency reveals strong spatiotemporal heterogeneity. The annual average production efficiency ranges from 0.660 to 0.674 and is higher in southern China. About 62.5 % of wind farms in the Yangtze River Delta exhibit high growth in efficiency. Environmental efficiency is high, especially in the southeast coastal region, whereas economic efficiency lags behind. Over 60 % of farms exhibit low economic efficiency, and the first post-subsidy year sees a 3.03 % decline. The capacity factor is positively associated with all four efficiency dimensions, with contribution thresholds ranging from 0.32 to 0.41. Leading turbine brands and central state-owned enterprises achieve superior environmental efficiency. The learning-by-doing effect displays dimensionally heterogeneous associations with efficiency. Installed capacity, GDP, and industrial structure exhibit nonlinear relationships with each efficiency dimension. Interaction analysis reveals that a high capacity factor exhibits a stronger positive correlation with environmental efficiency in non-central state-owned enterprise projects. The capacity factor, learning-by-doing, and scale expansion jointly show a positive relationship with comprehensive efficiency. These findings support China’s transition in offshore wind power from scale-focused to quality- and efficiency-driven development.