NEC 2026 Code Changes: Top 10 Updates Affecting Solar Installers

Published July 28, 2026 — PES Supply Technical Brief

The National Electrical Code (NEC) runs on a fixed three-year cycle, and the 2026 edition of NFPA 70 has been published by the National Fire Protection Association (NFPA). For solar installers, the 2026 NEC brings meaningful revisions to Articles 690 (Solar PV Systems), 705 (Interconnected Power Sources), and 706 (Energy Storage Systems) — the three articles that govern most residential and commercial solar work. While none of these changes apply until your specific state or county adopts the 2026 code, early adoption is already underway, and designers need to be prepared ([Heaven Designs](https://heavendesigns.in/blog/nec-code-changes-solar-designers/), [NFPA](https://www.nfpa.org/codes-and-standards/nfpa-70-standard-development/70)).

At PES Supply, we help installers and contractors navigate code compliance across 50,000+ SKUs from 169 authorized brands. This guide walks through the ten most impactful NEC 2026 changes for solar professionals and what they mean for your next installation.

1. New Fractions-of-Ampere Rule (Article 690.4(G))

NEC 2026 introduces a new fractions-of-ampere rule under Article 690.4(G) that affects how PV circuit calculations are performed. Previously, installers could round current values in ways that sometimes resulted in undersized conductors or overcurrent protection devices. The new rule requires that fractions of an ampere be handled consistently, closing a loophole that allowed designers to drop decimal values when sizing PV system circuits.

In practice, this means you can no longer round down short-circuit current (Isc) or operating current values to the nearest whole ampere when performing conductor sizing calculations. The change is subtle but important — it may push some designs to the next standard conductor size, particularly on systems operating near the boundary of a given ampacity rating.

2. Removal of the 100 kW Threshold (690.7(A)(3) and 690.8(A)(1)(a)(3))

One of the most significant structural changes in NEC 2026 is the removal of the 100 kW cap on engineer-calculated PV voltage and current. Under prior editions, systems rated above 100 kW required different calculation methodologies than smaller systems, creating a design discontinuity for commercial and C&I projects in the 100–500 kW range.

The 2026 code removes this threshold entirely, allowing the same engineer-calculated methods to apply regardless of system size. For installers working on commercial rooftops and small utility projects, this simplifies the design process and eliminates a regulatory cliff that previously forced design changes at the 100 kW mark.

3. Bifacial Module Current Calculation Method (690.8(A)(1)(a)(2))

As bifacial modules have become the default for ground-mount and many rooftop installations, the NEC has struggled to provide clear guidance on how to account for the additional rear-side energy harvest. NEC 2026 addresses this with a new bifacial-friendly current calculation method under Article 690.8(A)(1)(a)(2) that allows designers to use manufacturer-provided instructions for determining bifacial module current.

This is a meaningful change because bifacial modules can produce 5–25% more energy than their monofacial counterparts depending on albedo, mounting height, and ground clearance. The new method gives designers a code-compliant path to account for this additional current without relying on generic derating factors that may understate or overstate real-world performance.

Bifaciality Factor	Rear-Side Contribution	Typical Application
70%	Minimal gain	Low-albedo rooftop
80%	5–15% additional yield	Standard ground-mount
85–90%	15–25% additional yield	High-albedo, elevated mount

Browse our selection of bifacial and monofacial modules at solar panels to find products with manufacturer-published bifaciality data.

4. Rapid Shutdown Reorganization (690.12(C))

Article 690.12 governs rapid shutdown (RSD) for PV systems installed on or in buildings, protecting emergency responders from high-voltage DC shock hazards. The 2026 code reorganizes the initiation-device language under 690.12(C) without changing the underlying performance targets, but adds an important new allowance for E-stop style switches.

Performance Requirements (Unchanged)

The core rapid shutdown performance requirements remain the same as in NEC 2023 ([SurgePV](https://www.surgepv.com/blog/solar-nec-compliance-usa)):

• Outside the array boundary (more than 1 ft from the array perimeter): controlled conductors must be reduced to 30V or less within 30 seconds of initiation.
• Inside the array boundary (within 1 ft of the array perimeter): controlled conductors must be reduced to 80V or less within 30 seconds of initiation.

What Changed

The reorganization clarifies the types of initiation devices that are acceptable, explicitly allowing E-stop style emergency switches that meet the listing requirements. This gives installers more flexibility in how they design the shutdown initiation circuit, particularly on commercial projects where a dedicated E-stop may be more practical than relying solely on the service disconnect.

Compliance paths remain the same: module-level power electronics (microinverters and DC optimizers that shut down inherently), dedicated module-level rapid shutdown devices behind each module, and — for ground mounts and some flat-roof layouts — array-boundary exceptions that allow string-level shutdown.

5. DC Disconnect Requirements (690.13)

NEC 690.13 requires a readily accessible disconnecting means for every PV system tied to a building's wiring. The 2026 code maintains this requirement but aligns it more closely with the reorganized rapid shutdown language. For grid-tie systems, two separate disconnect points are typically needed: one on the DC side between the array and the inverter, and one on the AC side between the inverter and the utility meter ([Sun Supply PV](https://sunsuppv.com/solar-ac-and-dc-disconnect-switches-for-grid-tie-systems/)).

Key Sizing Considerations

• DC disconnects must be rated above the system's actual operating voltage and current, with margin. Most residential string systems use 600V, 30–60A rated disconnects; commercial arrays may need 1000V-rated switches.
• Outdoor-mounted disconnects require a minimum NEMA 3R enclosure for rain and dust protection. Indoor disconnects can use NEMA 1 enclosures.
• Fused DC disconnects add overcurrent protection at the disconnect point, which some AHJs require for multi-string arrays feeding a combiner.
• Fire code in most jurisdictions requires the disconnect to be lockable in the open (off) position so first responders can isolate the array.

Shop our full range of disconnects and balance of system components to ensure your installations meet the latest code requirements.

6. GFCI and Arc-Fault Protection Updates (210.12, 210.17)

The 2026 NEC enhances arc-fault protection requirements in dwelling units under Articles 210.12 and 210.17. While these sections primarily address general dwelling-unit wiring, they have direct implications for solar installations — particularly for PV systems that feed into dwelling unit panels or share circuits with protected loads.

The enhanced requirements expand the scope of arc-fault circuit interrupter (AFCI) protection and tighten coordination between AFCI and ground-fault circuit interrupter (GFCI) devices. For solar installers, the key takeaway is that the point of interconnection — where the PV system ties into the building's electrical system — may require additional protection coordination to avoid nuisance tripping.

DC Arc Fault Protection for PV Systems

Separate from the general dwelling-unit requirements, PV-specific DC arc fault protection remains a critical code requirement. Article 690.11 requires arc-fault circuit protection for PV systems with DC source circuits on or penetrating buildings. Many modern inverters include this protection built-in, but installers using string inverters without integrated AFCI must add external arc-fault protection devices.

7. Reinstated Conductor-Length Limit (705.11(C)(1))

Article 705 governs interconnected power sources — the point where your PV system connects to the grid. NEC 2023 dropped a conductor-length limit that had previously existed in this article, but the 2026 code reinstates it under 705.11(C)(1). This limit restricts the length of conductors between the interconnection point and the overcurrent protection device.

For installers, this means closer attention to conductor routing on the AC side of the system. The reinstated limit prevents excessively long unprotected conductor runs that could create hazards if damaged. Plan your AC interconnection wiring to keep conductor lengths within the code-specified limits, particularly on systems where the inverter is located far from the main service panel.

8. Energy Storage System Changes (Article 706)

NEC 2026 makes significant changes to Article 706, which governs energy storage systems. The most notable change is the deletion of section 706.16, which previously contained specific requirements for storage backup systems. Instead, the 2026 code routes most storage backup systems through Article 702 (Optional Standby Systems), simplifying the regulatory framework for residential battery installations.

New Backup-Power Option (702.4)

The code adds a new backup-power option under 702.4 for one- and two-family dwellings, providing clearer requirements for how battery storage systems function as backup power sources. This change aligns the NEC with the growing trend of residential solar-plus-storage installations and provides installers with a more straightforward compliance path for home battery systems.

Key requirements for ESS installations under the 2026 code include:

• A documented Emergency Operations Plan covering safe shutdown procedures for BESS sites.
• Annual safety inspections and safety data sheet documentation.
• Clearer disconnecting-means requirements, including location and control specifics for storage systems in dwellings.
• Formal system commissioning at installation and ongoing maintenance logging.

Explore our battery energy storage and inverter selections for components that meet the latest Article 706 requirements.

9. Labeling Requirements Consolidation (690.7(D), 690.12(D))

The 2026 NEC continues the labeling reorganization that began in the 2023 edition. Key changes include:

• DC voltage marking requirements are now consolidated under 690.7(D), providing a single reference point for voltage labeling on PV equipment.
• Rapid shutdown labeling is consolidated under 690.12(D), streamlining the labeling requirements for RSD initiation devices and array boundary markers.
• Definitions that previously lived in Article 690 have been moved to Article 100, aligning PV terminology with general code definitions.

Common Labeling Points

Solar labels are commonly required at the following locations ([pvlabels.com](https://www.pvlabels.com/solar-placement-guide/)):

Location	Label Type	Key Information
Inverter	AC Disconnect	Operating voltage, current, dual power supply warning
DC Disconnect	PV System DC Disconnect	Operating voltage (Vdc), operating current (A), max system voltage, short circuit current
Rapid Shutdown Switch	RSD Label	"Turn Rapid Shutdown Switch to Off position to shut down PV system"
Service Equipment	Service Disconnect	Multiple sources warning, overcurrent device ratings
Combiner Box	PV Power Source	Max DC voltage, circuit identification
Battery/ESS	ESS Disconnect	Nominal AC voltage, max DC voltage, available fault current

Verify that older plan templates and pre-printed labels reflect current section numbers — a paperwork detail that can hold up an inspection if missed.

10. Interconnection Rule (705.12) and the 120% Rule

The NEC 705.12 interconnection rule, commonly known as the "120% rule," remains a critical compliance point for solar installations. Under this rule, the total rating of all overcurrent devices supplying a panelboard — excluding the main supply overcurrent device — must not exceed 120% of the panelboard's busbar ampacity.

For a common 200-amp service panel, this typically leaves room for about a 40-amp solar breaker before a panel upgrade or line-side connection is required ([SolarFY](https://mysolarfy.com/solar-permits-and-interconnection/)). The 2026 code maintains this requirement but the labeling changes under 690.7(D) and 690.12(D) affect how the interconnection point is marked.

State Adoption Timeline

The NEC is not law until a state or city adopts it, and adoption lags significantly. As of 2026, jurisdictions enforce editions ranging from 2014 through 2023, with the 2020 edition being the most common ([SurgePV](https://www.surgepv.com/blog/solar-nec-compliance-usa)). However, early adopters are already moving to the 2026 code:

• Colorado: The Colorado Electrical Board approved adoption of the 2026 NEC on May 27, 2026, with an anticipated adoption date of August 1, 2026. All new project submittals to Denver Community Planning and Development must comply with the 2026 NEC as of that date ([Denver.gov](https://www.denvergov.org/Government/Agencies-Departments-Offices/Agencies-Departments-Offices-Directory/Community-Planning-and-Development/CPD-News-and-Events/CPD-News/2026/New-electric-standards-to-be-effective-Aug.-1)).
• Massachusetts: Adopted the 2026 NEC with Massachusetts Amendments ([NFPA](https://www.nfpa.org/for-professionals/codes-and-standards/standards-development/nfpa-codes-and-standards-with-jurisdictional-changes)).

Always verify which NEC edition your local Authority Having Jurisdiction (AHJ) has adopted before finalizing a design. A detail that passes under NEC 2014 can fail under NEC 2020, and the same applies as jurisdictions transition to the 2026 code.

Preparing for the Transition

Update Design Templates

Plan sets built on NEC 2023 templates will start failing plan check as states adopt the 2026 code. Review your standard design templates, single-line diagrams, and labeling specifications to ensure they reflect the updated section numbers and requirements.

Train Your Team

Multiple training providers — including Mayfield Renewables, Solar Energy International, and licensing-renewal course platforms — have already published NEC 2026 summaries and training materials. Invest in continuing education for your design and installation teams before your jurisdiction adopts the new code.

Verify Component Listings

Ensure that all components — rapid shutdown devices, DC disconnects, inverters, and energy storage systems — are listed to the standards referenced in the 2026 code. Verify UL 1741 listing for rapid shutdown devices and confirm that ESS components meet the updated Article 706 requirements.

Plan for Procurement Lead Times

As jurisdictions adopt the 2026 code, demand for compliant components will increase. Plan for 7-10 business days delivery on stocked components and order early for projects in jurisdictions that have announced or completed adoption.

Conclusion

The NEC 2026 changes are evolutionary rather than revolutionary, but they reflect the industry's shift toward bifacial modules, integrated storage, and more precise system design. Installers who update their templates, train their teams, and verify component compliance now will be well-positioned as adoption spreads. The four sections that generate the most failures remain rapid shutdown (690.12), conductor sizing (690.8), labeling (690.56/690.7(D)), and interconnection (705.12) — put these in your design checklist, not your punch list.

PES Supply carries 50,000+ SKUs from 169 authorized brands to support your code-compliant installations. Browse our solar panels, inverters, energy storage, racking and mounting, and balance of system categories for components that meet the latest NEC requirements.