As the share of fluctuating electricity producers (PV and wind power) continues to grow, electric energy storage systems will have to fulfill more and more functions in the grid. Batteries play a particularly important role here. From commercial and industrial storage systems to utility-scale storage systems for multi-use cases, the requirements are increasing. Key quality indicators are not only safety (including functional safety) but also reliability as well as performance, defined by efficiency and effectiveness, over an ideally long service life. Compliance with site-specific requirements, such as noise generation, is also important. In this session, these aspects will be examined from different points of view, providing recommendations beyond existing standards based on operating experience.