This book addresses one of the most important legal instruments that can help combat climate change, namely Power Purchase Agreements. As decarbonisation is essential for the global transition to electricity, these contracts are a direct legal link that can be formed between the power producer and the power buyer. This type of contract plays an important role in stimulating the creation and development of more renewable energy projects, such as wind, solar or hydro, by providing secure and long-term revenues for producers, while customers benefit from long-term price predictability. The implementation and development of the signing of these contracts are evaluated in this research, with taking into consideration both the economic, legal and social impacts, as well as the effects on the environment. The analysis addresses the risks to which the parties are subject once these contracts are signed, the key factors that influence the development of these contractual relationships, with consideration of concrete cases where PPA market is a developed one, as well as examining these contracts with other legal financial instruments that have the same purpose and aim, namely Contracts for Difference.