This essential describes the regulatory framework of energy economics under which energy storage systems can operate today in conjunction with other flexibility options. Since storage systems are treated as final consumers, charges, fees, and levies may generally apply when purchasing electricity for a storage system. Therefore, several exemptions from charges, fees, and levies, which are presented in this book, are of great practical relevance. Additionally, the legal framework for participation in various markets that are relevant for storage systems is outlined. The book also provides an in-depth insight into regulatory developments.