The optimal level of overplanting for offshore wind in Germany should not exceed 5% to 10%, meaning the current 20% rule would impose unnecessary economic costs, according to a study by Frontier Economics.
German Federal Maritime and Hydrographic Agency (BSH) has proposed overplanting in its 2025 spatial development plan as a way to reduce grid costs for future offshore wind expansion. The 20% overplanting requirement would oblige developers to install capacity 20% above the level allocated through the grid connection.
The study, commissioned by the German Offshore Wind Energy Association (BWO) and the German Association of Energy and Water Industries (BDEW), analysed four development areas in the German North Sea.
“In those areas, the economically optimal level of overbuilding is around 5-10%. The associated curtailment of electricity generation is about 3-4%. From the perspective of individual projects, however, the optimum is lower – around 2.5–5%,” said Matthias Janssen, executive director at Frontier Economics.
“A blanket obligation to overbuild capacity by 20% would unnecessarily increase economic costs,” said Stefan Thimm, managing director of the German Offshore Wind Energy Association.
“Those who unilaterally try to save money on network expansion risk creating an unnecessary burden for electricity customers. We need to consider optimisation potential holistically – from spatial planning and grid connections to market mechanisms,” he added.
“From the industry’s perspective, three measures should take priority: a lower power density of less than 10 MW per square kilometre in new areas; spatial planning that reduces shading effects between wind farms; and stronger international cooperation – for example through the development of suitable offshore areas in Denmark. This is the only way to advance offshore wind development in a cost-effective way,” Thimm said.