Solar and Batteries in the Code: Articles 690, 705 and 706

By IES team, Innovative Electrical Services (IES), Auburn, CA · Reviewed November 2026 · 3 min read

Key takeaways

Article 690 covers the solar array itself, including rapid shutdown on buildings (690.12).
Article 705 covers connecting any power source to the building wiring, including the 120% busbar rule.
Article 706 covers energy storage systems such as home batteries.
Fire codes (NFPA 855 and the California Fire Code) also limit battery size and location in homes.

A home solar and battery system touches several parts of the NEC at once. Knowing which article covers which piece helps make sense of permit comments and design choices.

Article 690: the solar array

Article 690 covers photovoltaic (PV) systems: modules, wiring, inverters, disconnects and labels. One of its most familiar rules is rapid shutdown (690.12). For PV on buildings, firefighters need a way to quickly reduce the voltage in the array wiring on and near the roof. That is why modern rooftop systems use module-level electronics or other listed rapid shutdown equipment, with an initiation switch and labels at the service.

Article 705: connecting to your wiring

Article 705 covers interconnecting any power source, solar, batteries or generators, with the building’s other wiring. For a load-side connection (a breaker in an existing panel), 705.12 protects the panel busbar from being overloaded by two sources feeding it at once.

The most-used option is the 120% rule: 125% of the inverter’s output current, plus the main breaker rating, can’t exceed 120% of the busbar rating. The solar breaker goes at the opposite end of the busbar from the main, and a warning label says not to move it.

Example of the 120% rule for a load-side solar connection: a 200 A busbar with a 200 A main leaves room for 40 A of backfeed breaker, which fits an inverter up to 32 A output. The solar breaker goes at the opposite end from the main.

Try it

When the numbers don’t work, other options include a supply-side connection, a smaller main breaker (if the load calculation allows), a panel with a larger busbar, or a listed power control system that limits current. Each has its own rules.

Article 706: energy storage systems

Article 706 applies to energy storage systems (ESS) such as home batteries. Highlights:

It applies to systems over 1 kWh.
Equipment must be listed, and the ESS needs a disconnecting means, with labels showing where it is.
Installation follows the maker’s instructions and the listing, which often set clearances and locations.

Fire code limits for homes

Battery size and placement in homes is also governed by NFPA 855 and the fire codes based on it. Paraphrasing the residential chapter: individual units are generally limited to 20 kWh, and the total in one area is capped, at 40 kWh in places like utility closets, basements and storage spaces, and at 80 kWh in garages, accessory structures, on exterior walls and outdoors. Sleeping rooms, closets that open into them, and habitable living spaces are generally not allowed locations. California’s fire and residential codes have their own versions, so the local fire authority’s reading matters.

Utility rules are separate

PG&E and other utilities also review interconnections, and their requirements (meter location, disconnect access, export limits) sit on top of the code. Our homeowner guide on solar permits and interconnection covers that side.

Sources and further reading

Local rules decide. These articles explain general ideas and point to the code sections we use. They are not legal or engineering advice and don’t replace the code itself. California adopts the NEC with its own amendments, cities and counties can add more, and the local inspector (the AHJ, or authority having jurisdiction) has the final say on any job. Read the code free at NFPA’s free access page.