This article analyzes the main technical requirements for the installation of internal electrical networks in buildings. Internal electrical wiring is one of the most responsible parts of a building’s power supply system. Poor design or improper installation may cause electric shock, fire, short circuit, overheating of cables, premature failure of equipment and increased energy losses. The article discusses load calculation, selection of cable cross-section, circuit breakers, residual current devices, grounding systems, cable routes, distribution boards, wet rooms and fire-risk areas. The study is based on the IEC 60364 series, NFPA 70 National Electrical Code and international approaches to low-voltage electrical installations. IEC 60364-1:2025 defines the scope, fundamental principles and safety requirements for low-voltage electrical installations, while IEC 60364-5-52 covers the selection and erection of wiring systems. NFPA 70 is widely presented as a benchmark standard for safe electrical design, installation and inspection.