Sustaining Wind Power Output After Feed-In Tariffs End: Plant-Level Evidence on Ageing and Support Exit in Türkiye

The contribution of wind power to a sustainable energy transition depends on how long installed turbines keep delivering energy. Support schemes often last ten years, while turbines run for twenty or more. In the United States, performance falls by 3.6% to 4.7% after the ten-year production tax credit expires; we know of no comparable test for a feed-in tariff. We assemble hourly generation for Türkiye’s licensed wind plants for 2014–2026 from the EPİAŞ Transparency Platform, link each plant to the YEKDEM feed-in scheme, and normalise output with ERA5 wind at each site. In a stacked event study of 44 plants that completed their support term, performance in the three years after exit is 1.5% lower than before (95% CI −3.5% to +0.4%). The difference comes from hours with near-zero day-ahead prices, in which plants out of support reduce output; public data cannot identify the cause of these reductions. Outside these hours, the difference is 0.5%, and falls above 3% are ruled out across robustness checks. Within-plant performance declines by 0.51% per year of age, and by 0.25% outside near-zero-price hours. Time-limited feed-in support therefore need not reduce the long-term output of existing renewable capacity.