NFPA 70 National Electrical Code (NEC) — Article 706: Energy Storage Systems
NFPA 70, the National Electrical Code (NEC), is the foundational US electrical safety standard adopted by statute in approximately 49 states, and Article 706 specifically governs the installation of stationary Energy Storage Systems (ESS) including lithium-ion battery banks, flow batteries, and capacitor-based systems. Article 706 was introduced in the 2017 NEC edition and establishes requirements for disconnecting means, overcurrent protection, circuit sizing, product listing, commissioning, ventilation, and emergency shutdown functions for permanently installed ESS operating above 50 V AC or 60 V DC. The NEC is revised on a 3-year cycle; the 2026 edition is current. Any stationary battery installation in a US commercial, industrial, or residential building must comply with Article 706.
Published by: National Fire Protection Association (NFPA)
Current edition: NFPA 70-2026 (NEC 2026), Article 706
Revision cycle: Every 3 years (2017 introduced Article 706; 2020, 2023 and 2026 editions revised it). The 2026 edition reorganises several Chapter 2 articles, separates requirements for 1000 V AC and 1500 V DC systems, and updates provisions for EV charging equipment, solar generation equipment, and battery energy storage facilities.
Scope
Article 706 applies to permanently installed ESS operating above 50 V AC or 60 V DC. Key requirements include:
- Product listing: ESS equipment must be listed (UL 9540 is the primary listing standard referenced)
- Disconnecting means: Readily accessible disconnect required to isolate ESS from all wiring; emergency shutdown function for one- and two-family dwellings
- DC voltage limits: 100 V DC ceiling for one- and two-family dwellings; higher voltages permitted where live parts are inaccessible during routine maintenance
- Overcurrent protection and charge control: Circuit sizing and protection requirements for ESS output circuits
- Commissioning: Verification of correct installation and function required (except for one- and two-family dwellings)
- Ventilation: Adequate ventilation to prevent gas accumulation; ESS room personnel doors must open in direction of egress and be equipped with panic hardware
Relationship to other standards
NEC Article 706 defines electrical installation requirements; NFPA 855 defines siting, separation distances, and fire suppression requirements for stationary ESS. UL 9540 is the product listing standard referenced by Article 706; UL 9540A is the fire propagation test method. NFPA 13 covers sprinkler design for ESS rooms. NFPA 111 governs stored-energy emergency and standby power systems. IEEE 1547 covers grid interconnection of battery energy storage systems. Together, NEC Article 706 plus NFPA 855 plus UL 9540 form the core US regulatory framework for commercial and utility BESS installations.
Disclaimer: This is not a definitive guide, just an indication and it is important that you always go back to the source for legislation.