NEC 2026: What Changes for Solar Designers

The National Electrical Code runs on a three-year cycle, and the 2026 edition of NFPA 70 has already been released. If you design or stamp solar permit sets in the United States, the question is not whether change is coming. It already happened. The real question is which of those changes touch the drawings you are producing this week, and which ones will not matter until your local AHJ formally adopts the 2026 edition, which for most jurisdictions is still months or years away.

Direct answer. NEC 2026 is published and confirms changes to Articles 690, 705, and 706. Article 690 gets a new fractions-of-ampere rule, removes the 100 kW cap on engineer-calculated PV voltage and current, and adds a manufacturer-instruction method for bifacial module current. Article 690.12 reorganizes rapid shutdown initiation-device language without changing the underlying performance targets. Article 705 restores a conductor-length limit that was dropped in 2023. Article 706 removes 706.16 and routes most storage backup systems through Article 702 instead. None of this applies to your project until your specific state or county adopts the 2026 code, which is the part every designer still needs to track manually.

Solar permit designers, PE reviewers, and AHJ plan checkers all work off whichever NEC edition the local jurisdiction has adopted, and that adoption date rarely lines up with the NFPA release date. This guide separates the confirmed 2026 code text from the local adoption timeline, article by article, so you can tell your team exactly what to change and exactly what to wait on.

The NEC Revision Cycle, and Why “2026” Does Not Mean “In Effect Everywhere”

The National Fire Protection Association revises NFPA 70 on a fixed three-year schedule: 2020, 2023, 2026, and now 2029 in development. Each cycle moves through public input, a first draft, public comment, a second draft, and final action at NFPA’s annual technical meeting before the new edition is published. The 2026 edition has cleared all of that and is now available, including free read-only access through an NFPA account, as confirmed by HeatSpring’s release coverage.

This gap is why a solar permit designer cannot simply “switch to 2026” and move on. You have to track adoption jurisdiction by jurisdiction. A rooftop project in a state that adopted NEC 2023 late and has not scheduled a 2026 adoption cycle still gets stamped to 2023 rules. A project in a state that jumps on new editions quickly may already require 2026 compliance. This is functionally identical to the confusion that followed NEC 705.12 interconnection rules after the 2023 cycle, where designers who assumed uniform national adoption produced plan sets rejected on edition mismatch alone.

What’s Confirmed vs. What’s Still Being Decided

This is the single most important framing in the entire article, so it goes first, not buried at the end.

Confirmed, because NFPA has published the 2026 NEC text and multiple training providers (Mayfield Renewables, Solar Energy International, licensing-renewal course platforms) have summarized the section language directly:

• Article 690’s new fractions-of-ampere rule (690.4(G))
• Removal of the 100 kW threshold in 690.7(A)(3) and 690.8(A)(1)(a)(3)
• The new bifacial-friendly current calculation method in 690.8(A)(1)(a)(2)
• The 690.12(C) rapid shutdown reorganization and its allowance for E-stop style switches
• The reinstated conductor-length limit in 705.11(C)(1)
• The deletion of 706.16 and the new 702.4 backup-power option for one- and two-family dwellings

Still being decided, or not verifiable with a citable primary source at the time of writing:

• The exact state-by-state and county-by-county adoption schedule for NEC 2026. This is genuinely unresolved and moves on its own timeline in every jurisdiction.
• Section-level detail for Article 691 (large-scale PV electric supply stations). Multiple sources confirm changes exist for the 2026 cycle, but did not provide citable section text at the level of detail this article requires. We are not inventing article numbers here.
• Whether NEC 2026 introduces any change to DC arc-fault protection requirements under 690.11. No confirmed source surfaced a 2026-specific change to that section during this research pass, so this article does not claim one.
• Whether 705.12 itself, the load-side and supply-side interconnection framework including the 120% busbar rule, changed in 2026 beyond the confirmed 705.11(C)(1) conductor-length restoration.

Treat the first list as text you can plan drawings around once your AHJ adopts 2026. Treat the second list as open questions to verify against your specific state amendment and your local plan reviewer before you assume anything.

Article 690: PV Systems

Article 690 is the backbone of every PV permit set, and the 2026 edits are mostly clarifications rather than new performance requirements. Four changes matter for the drawings you produce.

According to Mayfield Renewables’ 2026 NEC update summary, four changes matter most for the drawings you produce.

Fractions of an ampere or volt (690.4(G)). A new subsection tells you what to do with a calculation result that lands on a fraction, for example 24.4 amps. After applying correction factors and conditions of use, results under 0.5 may be dropped. This sounds minor, but it removes a recurring point of disagreement between designers and plan reviewers on rounding practice for conductor and overcurrent device sizing.

No more 100 kW ceiling on engineer-calculated values (690.7(A)(3) and 690.8(A)(1)(a)(3)). Under NEC 2023, a licensed engineer could use calculation methods, instead of the standard table-based methods, to determine maximum PV system voltage and current, but only on systems above 100 kW. NEC 2026 removes that threshold entirely. A PE can now apply engineering calculation methods on a 12 kW residential rooftop system the same way they could previously on a 5 MW ground mount.

Manufacturer instructions as a current-calculation method (690.8(A)(1)(a)(2)). This is the change with the most day-to-day relevance for anyone specifying bifacial modules. Instead of relying solely on the standard nameplate-current-times-1.25 method, designers can now use the module manufacturer’s published instructions to calculate maximum circuit current, which tends to produce a more accurate figure for bifacial gain than the older blanket multiplier.

Disconnect reorganization (690.13). The system disconnecting means language now points to Article 705.20 and consolidates locking requirements under 110.25. The substantive requirement, a readily accessible way to disconnect the PV system from all conductors it supplies, has not changed. What changed is where you find the cross-reference.

Article 691: Large-Scale PV Electric Supply Stations

Article 691 governs utility-scale PV facilities with a generating capacity of at least 5,000 kW (5 MW) that are not under exclusive utility control. That scope threshold carries forward unchanged into 2026. Multiple training providers confirm that Article 691 received changes for the 2026 cycle, but the section-level detail was not available in a citable form during our research, so this article is not going to fabricate section numbers here. If your firm designs utility-scale interconnections, the practical move is to pull the actual 691 text from your NFPA read-only access or your code book once your project’s jurisdiction confirms a 2026 adoption date, rather than relying on secondhand summaries for anything above 5 MW.

Article 705: Interconnected Power Production Sources

Article 705 covers how PV, battery storage, generators, and other power sources connect to a building’s electrical system, and it is the article most directly tied to permit rejections on interconnection drawings.

The confirmed 2026 change here is the reinstatement of 705.11(C)(1), a conductor-length limitation for interconnecting power production source output conductors to service conductors. This exact provision existed in NEC 2020, was removed in the 2023 cycle, and comes back in 2026. The intent, per code summaries, is to reduce the length of unprotected conductor runs inside a building between the PV disconnect and the service equipment, which lowers exposure to arc and fault risk in an unmonitored conductor segment.

If your firm has been designing to NEC 2023 for the last cycle, this is the one change most likely to force a physical layout adjustment rather than a paperwork update, because it constrains where you can route conductors inside the structure, not just how you label them.

For the interconnection method itself, load-side tap versus supply-side connection and the 120% busbar rule under NEC 705.12, we could not verify a 2026-specific text change beyond the conductor-length restoration above. Continue designing to your jurisdiction’s adopted busbar and supply-side rules, referencing the NEC 705 glossary entry for the current definitions, and confirm directly with your AHJ before assuming anything shifted.

Article 706: Energy Storage Systems

Battery energy storage has been the fastest-growing line item on C&I and residential permit sets for the last two code cycles, and Article 706 reflects that with two structural changes documented by Solar Builder magazine’s 2026 NEC coverage.

706.15 now points to 705.20. The disconnecting means requirement for energy storage systems is aligned with the same 705.20 language used for PV and other power production sources. This is a consistency move, one disconnect standard across power source types instead of a separate ESS-specific version.

706.16 is gone. The 2023 edition’s “connection to energy sources” section is deleted entirely in 2026. The practical effect, according to code summaries, is that most residential and light commercial ESS installations providing backup power now fall under Article 702 (optional standby systems) rather than Article 710 (stand-alone systems). That reclassification matters because 702 and 710 carry different requirements for transfer equipment and load calculations.

New backup-power option under 702.4. One- and two-family dwellings get a third compliance path: a listed power control system meeting UL 3141 that automatically prevents overload during a utility outage. This gives residential BESS installers an alternative to full-load-calculated backup sizing, provided the control system is UL 3141 listed.

Rapid Shutdown (690.12): Reorganized, Not Redefined

Rapid shutdown is the section every residential installer asks about first, and it is worth saying plainly, per code training summaries of 690.12(C): NEC 2026 does not change the underlying rapid shutdown performance targets. The array boundary voltage and timing limits that solar installers have been designing and labeling to under NEC 2023 stay in place.

What changed is the structure of 690.12(C). The 2026 edition reorganizes the initiation-device requirements into clearer subdivisions covering device type and location, operation, and rules for buildings with multiple PV systems, aligning the section with the NFPA Style Manual’s formatting conventions. Two practical shifts come out of that reorganization:

1. A single, generalized “readily accessible” requirement now applies to all acceptable initiation devices, rather than repeating the phrase separately for each device type. That reduces the chance of a device being technically compliant on wording but flagged by a reviewer applying an outdated mental checklist.
2. The permitted initiation device list narrows to three types: the service disconnecting means, the PV system disconnecting means, and listed switches. The previous requirement that a switch plainly show “off” or “on” position is removed, which opens the door to emergency-stop (E-stop) style switches as a compliant initiation method.

If your firm has built a NEC 2023 rapid shutdown compliance checklist for permit review, or leaned on the rapid shutdown glossary definition to onboard new drafters, the underlying voltage and timing rules on that checklist do not need to change for 2026. What does need an update, once your AHJ adopts the new edition, is the initiation-device language and the E-stop switch allowance, so your plan set references the correct subsection numbering and does not get flagged for citing superseded structure.

Arc-Fault Protection and Enforcement Patterns to Watch

We could not confirm a specific NEC 2026 change to DC arc-fault circuit interrupter requirements under 690.11 during this research pass, and this article does not claim one exists. What is documented, and worth tracking as a designer, is the enforcement pattern around arc-fault protection more broadly, a pattern our NFPA 855 energy storage safety guide covers from the storage side: AHJs in states with a history of rooftop fire incidents have tightened field inspection scrutiny of arc-fault device listings and labeling over the last two code cycles, independent of whether the underlying NEC section text changed. That enforcement trend, plus the growth of battery storage sharing conductor runs with PV output circuits under the revised Article 706 framework above, is a reasonable signal that arc-fault and rapid shutdown interaction will get more attention in the next code cycle even where the 2026 text itself stayed quiet on 690.11.

The 3-Layer Adoption Check: A Framework for Preparing Now

Because NEC publication and NEC adoption are two different clocks, we use a simple three-layer check with every permit engagement to confirm which edition actually governs a given plan set before a single line gets drawn.

Apply this on your very next permit set, whether it targets NEC 2020, NEC 2023, or a jurisdiction that has already moved to 2026. The framework does not depend on which edition wins; it depends on confirming the edition before you draw the interconnection detail, the disconnect location, or the rapid shutdown initiation device.

Common Mistakes Designers Make Going Into a Code Cycle Transition

Assuming the newest edition applies everywhere. This is the single most common error during any NEC transition. A designer reads that NEC 2026 removed the 100 kW threshold on engineer-calculated values and applies that method to a project in a jurisdiction still enforcing NEC 2020, where the threshold still governs. The reviewer rejects the calculation basis, not the math.

Treating a reorganization as a new requirement, or vice versa. The 690.12(C) rapid shutdown language is reorganized in 2026, not substantively changed on performance targets. Designers who assume otherwise sometimes over-engineer a solution to a requirement that did not move, adding cost without a compliance benefit.

Missing the 706.16 deletion’s downstream effect. Because most ESS backup installations now route through Article 702 instead of Article 710, load calculation and transfer switch requirements shift with it. A designer who keeps citing 710 language on a project governed by the 2026 edition is citing a deleted framework.

Skipping the local amendment layer. Confirming the state’s adopted edition is necessary but not sufficient. County and city amendments frequently tighten interconnection or ESS placement rules beyond the base NEC text, and those amendments do not show up in a generic NEC summary article, including this one.

Want a sample of how we structure a rapid-shutdown and interconnection detail sheet for a current AHJ submission? Download a redacted permit packet sample to see the labeling and disconnect layout our team currently ships.

How Heaven Designs Helps

Tracking edition adoption across dozens of AHJs while still hitting a permit turnaround deadline is exactly the kind of variable-capacity problem a design partner should absorb instead of your in-house team.

• Solar Permit Design: PE-stamped plan sets in 4 to 7 business days, drafted to whichever NEC edition your specific state and county have adopted, not the newest one available.
• Solar Rooftop Detailed Engineering Design: full IFC-grade packages including single-line diagrams and disconnect layouts that reflect current Article 690, 705, and 706 cross-references.
• Download a sample deliverable: a redacted permit packet showing our current rapid shutdown and interconnection labeling approach.

Contact us if you want a jurisdiction-specific read on which NEC edition governs your next submission before you start drafting.

FAQ

Is the NEC 2026 edition already in effect?

The 2026 edition of NFPA 70 has been published and is available, including free read-only access through NFPA’s website. Whether it is “in effect” for your project depends entirely on whether your specific state or county has formally adopted the 2026 edition into its building code. Publication and local adoption are separate events, and adoption typically lags publication by months to years.

What changed in NEC 2026 rapid shutdown requirements?

The underlying rapid shutdown performance targets under 690.12 did not change in NEC 2026. The section was reorganized for clarity, the list of permitted initiation devices was simplified to three types (service disconnect, PV system disconnect, listed switches), the “readily accessible” language was generalized across all device types, and the requirement that a switch plainly show off or on position was removed, allowing E-stop style switches as a compliant option.

Does NEC 2026 remove the 100 kW limit for engineer-calculated PV values?

Yes. NEC 2023 restricted the use of engineer-calculated maximum voltage and current methods, as an alternative to standard table methods, to systems above 100 kW. NEC 2026 removes that threshold, so a licensed engineer can apply calculation methods to any size PV system, including small residential rooftop installations.

How does NEC 2026 affect battery energy storage system design?

Article 706 section 706.16 (connection to energy sources) is deleted entirely in the 2026 edition. Most residential and light commercial energy storage systems providing backup power now fall under Article 702 (optional standby systems) instead of Article 710 (stand-alone systems), which changes applicable load calculation and transfer equipment requirements. A new option under 702.4 also allows a UL 3141 listed power control system as an alternative compliance path for one- and two-family dwellings.

Did NEC 2026 change the 120% rule for solar interconnection under 705.12?

We could not confirm a 2026-specific change to the core load-side and supply-side interconnection framework or the 120% busbar rule under 705.12 during our research. The confirmed 2026 change in Article 705 is the reinstatement of a conductor-length limitation under 705.11(C)(1), which was in NEC 2020, removed in NEC 2023, and restored in NEC 2026. Confirm directly with your AHJ before assuming the 705.12 busbar rule itself has changed.

What is Article 691 and did it change for 2026?

Article 691 governs large-scale PV electric supply stations with a generating capacity of at least 5,000 kW (5 MW) that are not under exclusive utility control. Multiple code training sources confirm that changes were made to Article 691 for the 2026 cycle, but section-level detail was not available in a form we could verify and cite directly, so this article does not list specific 691 section changes. Utility-scale designers should pull the primary 2026 text once their project jurisdiction confirms adoption.

How do I know which NEC edition my AHJ has adopted?

Check your state’s building code adoption schedule first, since counties and cities cannot enforce an edition the state has not authorized, though they can layer local amendments on top of the state’s adopted edition. Then confirm directly with the specific plan reviewer for your project type, since adoption dates sometimes differ between residential, commercial, and utility-scale submittals within the same jurisdiction during a transition year.

Should I redesign existing NEC 2023 permit sets to NEC 2026 now?

Not unless your specific jurisdiction has already adopted the 2026 edition for your project type. Redesigning to an edition your AHJ has not adopted risks a rejection on the opposite basis, since the reviewer is checking against the currently adopted edition, not the newest one published. Track adoption status per project rather than switching your whole drafting standard at once.