With the increasing climate change crisis, the ongoing global energy security challenges, and the prerequisites for the development of sustainable and affordable energy for all, the need for renewable energy resources has been highlighted as a global aim of mankind. However, the worldwide deployment of renewable energy calls for large-scale financial and technological contributions which many States cannot afford. This exacerbates the need for the promotion of foreign investments in this sector, and protecting them against various threats. International Investment Agreements (IIAs) offer several substantive protections that equally serve foreign investments in this sector. Fair and Equitable Treatment (FET) clauses are among these. This is a flexible standard of treatment whose boundaries are not clearly defined so far. Investment tribunals have diverse views of this standard. Against this background, this article asks: What are the prominent international renewable energy investment threats, and how can FET clauses better contribute to alleviating these concerns? Employing a qualitative method, it analyses the legal aspects and properties of FET and concludes that the growing security and regulatory threats have formed a sort of modern legitimate expectations on the part of renewable energy investors who expect host states to protect them against such threats. Hence, IIAs and tribunals need to uphold a definite and broadly applicable FET approach to bring more consistency and predictability to arbitral awards. This would help deter many unfavourable practices against investments in this sector.