NEC Code Reference for Solar Installations (2026)

NEC Article 690 — Solar Photovoltaic (PV) Systems

690.4 — Installation Requirements

• All PV equipment must be listed for its intended use
• Inverters must be listed to UL 1741
• PV modules must be listed to UL 1703 or UL 61730
• Rapid shutdown devices must be listed to UL 3741

690.7 — Maximum Voltage

PV system DC voltage is limited based on location and use:

690.8 — Circuit Sizing and Current

690.9 — Overcurrent Protection

• Overcurrent protection required where conductor ampacity decreases
• Minimum size: 125% of continuous current
• DC-rated fuses/breakers required (not AC-rated)
• Each PV string requires individual fuse if 3+ strings in parallel

690.10 — Stand-Alone Systems

• Inverter output must supply the largest load (or have load management)
• Battery circuits sized at 125% of inverter continuous output
• Transfer equipment required if grid-connected backup

690.11 — DC Arc-Fault Circuit Interrupter

PV systems with DC conductors on or penetrating buildings must have DC AFCI protection. Detects and interrupts arcing faults on DC side.

690.12 — Rapid Shutdown

PV systems on buildings must have rapid shutdown that reduces:

• Conductors outside the array boundary to 80V within 30 seconds
• Conductors inside the array boundary to 80V within 30 seconds (2023 NEC)
• Must be UL 3741 listed system or module-level electronics

690.13 — PV Disconnecting Means

• Means to disconnect all ungrounded DC conductors
• Must be readily accessible
• Must be marked with rated voltage and current
• Can be load-break rated or non-load-break (with warning label)

690.31 — Wiring Methods

• Wiring must be rated for environment (sunlight, temperature, wet)
• PV Wire or USE-2 for exposed module connections
• THWN-2, XHHW-2 for conduit runs
• MC4 connectors or equivalent for module interconnects
• Conduit required when penetrating building envelope

690.41 — Grounding

• One conductor of a 2-wire PV system must be grounded (for systems < 50V)
• Systems ≥ 50V must have ground-fault detection and interruption
• Ungrounded systems require ground-fault detection on both poles
• Equipment grounding required for all exposed metal parts

690.46 — Ground-Fault Protection

All PV systems must have ground-fault detection and interruption (GFDI) for equipment and fire protection.

690.47 — Grounding Electrode System

PV systems must be connected to the building grounding electrode system. If separate electrode is installed, it must be bonded to the building system.

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