National Electrical Code (NEC)

The National Electrical Code (NEC), also known as NFPA 70, is the comprehensive set of electrical safety standards adopted throughout the United States. It governs the safe installation and maintenance of all electrical systems, including solar photovoltaic systems.

The NEC is published by the National Fire Protection Association (NFPA) and updated every three years — the current edition is NEC 2023, though many jurisdictions still enforce the 2020 or 2017 edition. For solar installations, the NEC covers everything from wire sizing and overcurrent protection to grounding, disconnects, labeling, and rapid shutdown requirements. Article 690 specifically addresses solar PV systems, while Article 705 covers interconnected power sources (connecting solar to the grid). Compliance with the NEC is mandatory for all permitted solar installations and is verified during the building inspection. Your solar installer designs the system to meet the NEC edition adopted by your local AHJ. Key NEC requirements that affect residential solar include rapid shutdown (690.12), the 120% bus bar rule for panel connections (705.12), and equipment grounding (690.43).