‘Energy security’ is a crucial concept in international relations, as well as in international (economic) law. Although no international legal definition of this multi-layered notion exists, and the concept has been recognized as ‘vague’ in international relations literature, it remains a term that is used time and again by states when referring to measures taken in connection with safeguarding their national energy supply. This contribution identifies the various dimensions of the concept of energy security, after which it studies its role in international (economic) law and zooms in on the World Trade Organization (WTO). It critically assesses how the panel and Appellate Body (AB) have dealt with WTO Members’ arguments connected to energy security in two recent WTO disputes, India – Solar Cells and EU – Energy Package. The article demonstrates that while energy security concerns may be a valid basis for defending a Member’s measure, they will not hold if that measure is applied in a discriminatory manner. This may be problematic, as energy security concerns are frequently geo-political in nature and may be inherently discriminatory. The contribution also explains why ‘long-term energy security’ defenses are more likely to meet the threshold of the Article XIV(a) General Agreement on Trade in Services (GATS) public policy exception, rather than the ‘products in local short supply’ exception of Article XX(j) GATT.