The larger the system, the more important the dimensioning of the electrical system becomes, as well as proactive planning and expandability, especially with regard to peak loads and safety. When energy recovery systems or various control systems are added, things quickly become very complex and confusing, but it doesn't have to be. A well-designed system for, for example, wellness and sauna facilities, an integrated energy recovery system, or even the integration of a photovoltaic (solar) system can be planned and implemented in the simplest way with just a few basic elements, which, however, must be correctly configured. For professional systems that are schematically interconnected, the VDE (Association for Electrical, Electronic & Information Technologies) and its standards naturally play a crucial role. Circuit breakers and fuses, cable cross-sections, and warning and emergency stop devices must be dimensioned and selected to ensure the protection of the system and personnel at all times. Planning these systems requires not only a high degree of accuracy and expertise in standards and..