By 2050, the European Union aims to become climate neutral. The achievement of this goal will require, among others, a massive boost in energy efficiency. Companies and other organizations can make a significant contribution to climate protection through systematic and long-term energy management. Since its publication in 2011, ISO 50001 became the most important international standard for energy management systems. The guide “energy management systems in practice” contains instructions, recommendation and practical examples that support organizations in implementing an energy management system according to ISO 50001:2018 based on an initial energy audit. For companies and organizations that initially want to assess if an energy management system is worthwhile, the guide contains a “test run“ which can be carried out with manageable effort. For those companies and organizations that want to go beyond energy management and address their environmental impacts comprehensively, the guide explains how to step up to EMAS, the eco management and audit scheme of the European Union.