ISO 50009:2021 is an international standard that provides guidance on how to implement a common energy management system in multiple organizations. The standard was developed by the International Organization for Standardization (ISO), an independent, non-governmental organization that sets worldwide standards for a variety of products and services. ISO 50009 is part of the ISO 50001 family of standards, which relate to energy management systems.

The standard is designed to help organizations to develop, implement, and maintain an energy management system that is effective and consistent across multiple sites. It provides guidance on how to develop a system that is tailored to the needs of each organization, while also ensuring that all of the components are compatible across multiple sites. This helps to save time and money, as well as reduce energy consumption and waste.

The standard is composed of four sections: energy policy, energy management system design, energy management system implementation, and energy management system maintenance. Each section provides guidance on the specific aspects of energy management systems and how they should be implemented.

The energy policy section provides guidance on how to develop an energy policy that is appropriate for the individual organization. This policy should be tailored to the needs of the organization, and should include objectives, targets, and other requirements. It should also specify how the organization will measure and track the performance of the energy management system.

The energy management system design section provides guidance on how to design an energy management system that meets the organization's needs. This includes guidance on how to identify the processes, controls, and other elements of the system. It also includes guidance on how to document and communicate the system to ensure that it is implemented correctly.

The energy management system implementation section provides guidance on how to implement the system. This includes guidance on how to develop and implement procedures, train personnel, and monitor and review the system.

Finally, the energy management system maintenance section provides guidance on how to maintain the system. This includes guidance on how to update the system, review and adjust the system, and communicate changes in the system.

Overall, ISO 50009:2021 provides clear and comprehensive guidance on how to implement a common energy management system in multiple organizations. This standard helps to ensure that organizations are able to effectively manage their energy use and save money in the process.