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The aim of this thesis was to investigate essential factors for wind turbines in Sweden, when they have reached their designed lifetime. Further, an additional aim was to develop a strategy for how to choose the most suitable end of life option. 

A literature review has been conducted to provide with overall information about the different options, lifetime extension, partial repowering, full repowering and lastly decommissioning. Interviews with company representatives were performed to receive useful data and information for the financial analysis and for the strategy. Lastly, the developed strategy has been applied to two case studies in Oxhult wind farm and Brunsmo wind farm in Sweden. 

The findings show that there are several factors to consider, firstly an assessment of the wind turbines needs to be conducted. Depending on the results from the assessment, a new approval of permits will be essential for a partial repowering or a full repowering. For lifetime extension spare parts are vital. This thesis provides developers with information and a basic strategy for how to perform an initial screening on how to choose the best option for a wind farm when it is approaching the end of its designed lifetime.