While the prices of energy generation are subject to significant fluctuations due to political and economic factors, energy supply contracts are usually concluded for the long term. To be able to pass on cost increases to consumers, these contracts typically include rights for the supplier to adjust prices. Over the past decade, the effectiveness of corresponding price adjustment clauses has regularly been the subject of legal disputes between the contracting parties. In this context, the courts, including the Federal Court of Justice (BGH), have developed a detailed catalog of requirements for the effectiveness of price adjustment clauses in energy supply contracts. This work presents these requirements in detail and analyzes the resulting implications for effective clause design, particularly in contracts.