Process-based Monte Carlo cost simulation for offshore wind farm decommissioning: A scenario analysis for the German North Sea

The decommissioning of offshore wind farms (OWFs) involves complex, multi-stage processes whose costs are subject to substantial uncertainty. With over 2,000 turbines approaching end-of-life in the German Exclusive Economic Zone (EEZ) alone, reliable cost estimation is essential for operators, regulators, and financial planning. Existing cost models are predominantly deterministic and lack industry-informed input parameters, correlation structures among risk drivers, or comprehensive scenario comparisons. Using a process-based Monte Carlo model with correlated operational and market risks, we estimate the cost distribution of offshore wind farm decommissioning across ten technological and logistical scenarios. Expected net costs in prices of 2022 range from approximately € 242,000 to € 543,000 per decommissioned MW across scenarios. Foundation removal dominates overall costs, accounting for roughly half of total expenditures, while partial decommissioning strategies significantly reduce expected costs. Vessel charter costs dominate. Partial decommissioning scenarios reduce expected costs by 18–27 % relative to the baseline. Feeder logistics concepts increase costs by 48–65 % due to additional vessels and amplified duration uncertainty. The widely used “installation backwards” approach is neither the most cost-effective nor the least risky option. Incorporating correlated risks substantially increases tail risk compared to deterministic estimates, suggesting that current provisioning approaches may underestimate financial exposure. ​