Were subsidy phase-outs premature for offshore wind power in China?

China's offshore wind capacity additions increased steadily during 2010–2020, surged in 2021 before the Feed-in Tariffs termination, then declined sharply by 76.32% in 2022. This boom-bust pattern raises critical questions regarding whether offshore wind power has attained sufficient techno-economic viability to independently compete in electricity markets and sustain project development, and whether subsidy phase-outs were premature. An integrated techno-economic analysis is conducted based on 117 offshore wind power plants approved during 2008–2021 and commissioned during 2010–2023, representing over 96% of China's cumulative installed capacity by the end of 2023. Results show that the levelized cost of electricity (LCOE) declined substantially from 1.610 to 0.406 (2023) CNY/kWh, narrowing its gap to plant-side grid parity from − 1.194 to − 0.013 (2023) CNY/kWh. Green certificates contribute supplementary revenues, but persistently low average prices constrain their effectiveness in offsetting offshore wind profitability shortfalls following subsidy phase-outs. Further dominant decomposition indicates that LCOE reductions were driven primarily by lifecycle cost declines (56.79%) rather than capacity factor improvements (40.81%), reflecting a learning-by-doing rate of 5.84% and supply-chain maturation supported by 34 newly-established specialized industrial bases. Accelerated cost reductions alongside a post-subsidy rebound in capacity additions indicate that technological innovation and industrial learning are increasingly capable of sustaining subsidy-free offshore wind development, once plant-side grid parity and profitability thresholds are approached. China's experience provides policy-relevant insights for emerging offshore wind markets on calibrating subsidy withdrawal timing to observed techno-economic performance, thereby reducing the risks of premature subsidy phase-outs and prolonged fiscal support for a more orderly market-oriented transition. • Subsidy withdrawal timing should be calibrated for market-oriented transition. • We collect data and conduct analysis of 117 offshore wind power plants in China. • Subsidy phase-outs were not premature in China as grid parity was nearly reached. • Lower lifecycle costs led to more reduction of LCOE than higher capacity factors. • Green certificates, due to lower prices, were insignificant revenue sources.