Disconnects and emergency shutdown for battery systems
A battery energy storage system needs a readily accessible disconnect inside the unit, within sight and within 10 ft of it, or, if out of sight, lockable. On one- and two-family homes, the system also needs an outdoor emergency shutdown switch.
What the code requires
Section 706.15 requires a means to disconnect an energy storage system, such as a home battery, from all wiring systems. The disconnect must be readily accessible and located in at least one of these ways: inside the energy storage system, within sight of and within 10 ft of it, or, if not within sight, lockable under 110.25. If remote controls not within sight operate it, the disconnect must be lockable and marked with where the controls are.
For one- and two-family dwellings, the system must have an emergency shutdown that stops it from exporting power to the home's wiring. The switch that starts the shutdown goes outside the building, must be readily accessible, and must show on and off. Turning it off performs the shutdown.
The disconnect must show whether it is open or closed, be labeled as the energy storage system disconnect, and be field-marked with the nominal output voltage of the system. Except at one- and two-family dwellings, the available fault current, an arc-flash label and the date of the calculation are also required. A shock-hazard warning is needed where both sides can be live while it is open.
Where circuits from the energy storage components pass through a wall, floor or ceiling, a readily accessible disconnect is needed within sight of the energy storage component; fused disconnects or circuit breakers can serve. Batteries serviced in the field separately from the electronics have added rules, including segmenting battery strings above 240 V dc.
On the job
- On a home battery at a one- or two-family dwelling, the system does not comply without the outdoor emergency shutdown switch.
- A disconnect that is not inside the system, not within sight and within 10 ft of it, and not lockable does not comply.
- Check that the disconnect is labeled as the energy storage system disconnect and clearly shows open and closed.
Exceptions that matter
- At one- and two-family dwellings, the energy storage system disconnect under 706.15(C) does not need the available fault current, arc-flash label or calculation-date markings. The 2023 text has no matching exemption for the separate battery disconnect markings in 706.15(E).
What changed in 2023
The 2023 NEC changed the location rule from within sight and lockable to any one of three options (inside the system, within sight and within 10 ft, or lockable if out of sight), replaced the 2020 rule for an outdoor disconnect or remote control at one- and two-family dwellings with an outdoor emergency shutdown function, and added 706.15(E) for batteries that are separate from the system electronics and serviced in the field.
Related sections
- NEC 706.7
- NEC 705.20: Disconnects for solar and other power sources
- NEC 110.25
- NEC 225.41
- NEC 230.85: Outdoor emergency disconnect for homes
- NEC 480.7
Where this comes from
- NFPA: 2026 NEC (A2025) CMP-13 First Draft public input report, reprinting 2023 text
- EC&M: Top Changes in the 2023 NEC for Energy Storage Systems (R. Mayfield), Feb 15 2024
- Electrical Contractor: Concluding the 2023 Code Review (M. Earley), Sep 11 2023
- Mike Holt: Summary of the 2023 Changes to the NEC
- Read the official NEC free at NFPA
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