A recent tide of ISDS cases in the renewable energy sector has generated a large number of arbitral awards that turn of the notion of legitimate expectations. The Fair and Equitable Treatment Standard (FET) and the notion of legitimate expectations has been highly undetermined in the past. This work contains a comprehensive analysis of the renewable energy awards and the interpretation of the notion of legitimate expectations therein. In particular, it is examined whether arbitral jurisprudence formed a cohesive body of caw-law. The author analyses which aspects with regard to commitment by the states, due diligence of the investors, and level of impact were considered a violation of the FET Standard by recent arbitral tribunals.