Solar One Line Diagram Requirements: The Installer's Guide

The one line diagram is one of the documents plan reviewers spend the most time on — and one of the most common sources of redlines on an otherwise complete solar permit package. Getting it right the first time keeps your project moving — getting it wrong means a resubmittal, a longer queue, and a delayed install date.

This guide covers what must be on every residential solar SLD, how NEC Article 690 requirements translate to specific diagram elements, and what changes when storage is added to the scope.

GreenLancer prepares permit-ready solar permit design plan sets with complete one line diagrams built to your AHJ's adopted code cycle. Sign up for free to get started.

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What Is a Solar One Line Diagram and Why Do AHJs Require It?

A solar one line diagram — also called a solar SLD or single line diagram — is the electrical roadmap of your PV system. It shows every major component, conductor size, OCPD rating, and interconnection method in simplified single-conductor notation.

AHJs require it because it's how they verify NEC compliance before a single wire gets pulled. The plan reviewer traces the full power path from modules through the inverter, disconnects, and conductors to the utility interconnection point, then cross-checks every callout against NEC requirements. When anything conflicts — a breaker size that doesn't match the calculation, or an inverter model that doesn't match the cut sheet — the application comes back.

One clarification worth making with your crew: a one line diagram and a three line diagram are not the same document. The one line shows system topology and ratings in simplified notation. A three line shows every conductor including grounding and neutral with actual wire routing detail. Most residential AHJs require a one line only. Some commercial jobs and utility interconnection applications for larger systems require both.

NEC 690 Requirements That Drive What Goes on the SLD

Most of what a plan reviewer checks on your SLD comes from NEC Article 690. The IAEI's overview of 2023 NEC PV changes is a solid reference if you're updating your templates for the current code cycle. Here are the specific sections that most directly affect what appears on your diagram.

NEC 690.7 — Maximum Voltage Marking

Maximum system DC voltage must be calculated and shown on the SLD — not just listed as module Voc. Temperature correction factors from NEC 690.7 apply and must be documented. Residential one and two family dwellings are limited to 600V DC maximum; commercial systems can reach 1000V or 1500V depending on equipment listing.

NEC 690.8 — Circuit Sizing and the 125% Multiplier

The 125% continuous current multiplier applied to Isc for DC source circuits is required — but it's only step one. Ambient temperature correction and conduit fill derating must be applied on top of the 125% multiplier. Stopping at 125% and skipping the derating chain is one of the most common calculation errors on submitted SLDs, and it shows up in plan check comments consistently.

The IAEI's PV electrical calculations article breaks down the full conductor sizing chain with worked examples.

NEC 690.9 — Overcurrent Protection

OCPD ratings must be shown for all DC source circuits, PV output circuits, and AC output circuits. Overcurrent devices used in DC circuits must be listed for DC use — standard AC breakers are not compliant and that gets caught on plan review. When OCPD is not required for smaller residential systems with adequate conductor ampacity, document the code basis on the SLD rather than leaving it blank.

NEC 690.12 — Rapid Shutdown on the SLD

The rapid shutdown initiator location must be shown on the diagram. Which conductors are subject to rapid shutdown control must be identified, along with the compliance pathway — inverter-integrated, MLPE, or a dedicated PV hazard control system. See our solar rapid shutdown requirements guide for the full breakdown.

NEC 690.13 — PV Disconnects

The PV system disconnecting means must be shown with its rating and location. If it's accessible to unqualified persons and conductors are energized at 30V or more, a lockable disconnect is required — note this on the SLD. AC disconnect location relative to the inverter and service equipment must be shown and consistent with the actual installation.

What Must Be on a Residential Solar One Line Diagram

This is what plan reviewers are looking for. Use this as a pre-submittal checklist before the package leaves your hands.

DC Side

• Module make, model, and quantity

• String configuration — number of strings and modules per string

• Maximum system DC voltage calculated with NEC 690.7 temperature correction

• Short circuit current (Isc) and maximum DC circuit current (Isc x 1.25)

• DC source circuit conductor size, type, insulation rating, and conduit type

• DC OCPD rating and listing confirmation (DC-rated fuse or breaker)

• DC disconnect location and rating

• Rapid shutdown initiator location and compliance pathway

• Equipment grounding conductor size per NEC 690.45 and 250.122, and grounding electrode system per NEC 690.47

Inverter

• Inverter make, model, and UL 1741 listing

• Maximum DC input voltage and current

• Nominal AC output voltage, frequency, and current

• Maximum continuous AC output current

• Confirmation that the inverter is utility-interactive listed

AC Side

• AC output conductor size, type, and conduit

• AC OCPD rating at 125% of inverter continuous output current

• AC disconnect location and rating

• Interconnection method and applicable NEC section identified — NEC 705.12(B) option number for load-side connections, NEC 705.11 for supply-side connections

• Backfed breaker size and busbar rating for 120% rule documentation (load-side jobs)

• Service panel main breaker rating and busbar rating shown separately — these are not always the same number

General Notes and Title Block

• Applicable NEC edition and any local amendments

• Project address and AHJ jurisdiction

• Installer or design firm name and contact

• Drawing scale or "not to scale" notation

• Revision date and version number

Why Solar One Line Diagrams Get Rejected at Plan Check

Most rejections aren't from major design errors. They're from specific, documentable mistakes that a thorough plan reviewer will catch every time.

DC Side Rejections

• 125% multiplier applied but temperature correction and conduit fill derating not shown

• DC OCPD not confirmed as DC-listed

• Conductor insulation type not called out — USE-2 vs. PV wire vs. THWN-2 in conduit are not interchangeable on the SLD

• Maximum system voltage listed as module Voc without temperature correction applied

AC Side Rejections

• AC OCPD size not matching the 125% continuous output calculation

• Backfed breaker size and busbar rating conflict with the 120% rule — see our 120% rule guide for the full calculation

• Interconnection method shown without identifying the applicable NEC section — supply-side jobs under NEC 705.11 are documented differently than load-side jobs under NEC 705.12(B)

• Interconnection method shown doesn't match the actual panel configuration

Rapid Shutdown Rejections

• Initiator not shown on the SLD

• Compliance pathway not documented

• Label wording doesn't match NEC 690.12(D) requirements for the adopted code cycle — this is especially common when templates haven't been updated for the current NEC edition

Service Equipment Labels and Power Source Identification

Plan check rejections don't always come from the electrical design. A clean SLD can still hold up a submittal if the labeling documentation is incomplete.

NEC 2023 Section 690.56 requires identification of power sources at service equipment when a PV system is interconnected. NEC 705.10 requires service equipment to be labeled to identify all power sources. These requirements go beyond the rapid shutdown placard and apply to the service panel, main disconnect, and any point where the utility and PV system share equipment.

Utilities sometimes have their own labeling requirements on top of NEC. Confirm with the AHJ whether they want labeling notes shown directly on the SLD, called out in the plan notes, or included as a separate labeling sheet. See our solar labeling requirements guide for a full breakdown of what's required and where it needs to appear.

General Rejections

• Equipment model numbers on the SLD don't match cut sheets

• NEC edition referenced in notes doesn't match what the AHJ has adopted

• EGC sizing not shown or not consistent with NEC 690.45 and 250.122; grounding electrode system not documented per NEC 690.47

The DOE's solar permitting resource notes that permitting soft costs remain stubbornly high across the U.S. — most of that comes down to resubmittals that a thorough SLD review would have prevented.

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How Solar One Line Diagram Requirements Change for Storage

Adding battery storage to a solar job changes the SLD significantly. How it changes depends on the coupling method. In an AC-coupled system, the battery inverter connects on the AC side of the main inverter and must appear on the SLD as an additional interactive source — not a load — with its own OCPD, conductors, disconnect, and listing information.

In a DC-coupled system, the battery charge controller or hybrid inverter sits on the DC side of the system, and the SLD documentation focuses on the DC interconnection point, charge controller ratings, and how the battery connects to the inverter rather than as a separate AC source.

The 120% busbar calculation must account for both the PV backfed breaker and the battery inverter contribution. Treating the battery inverter as a load rather than an interactive source is one of the most common errors on AC-coupled retrofit SLDs.

Our solar battery storage permit guide covers ESS interconnection requirements in detail, including how Article 706 and NFPA 855 documentation interact with the electrical SLD.

What to Add to the SLD for a Solar Plus Storage Job

• Battery system make, model, and UL 9540 listing

• Battery inverter make, model, and UL 1741 listing

• ESS disconnect location and rating per NEC Article 706

• Updated interconnection point showing both PV and ESS sources

• EMS documentation if NEC 705.13 is used as the compliance path

How SLD Requirements Vary by AHJ

The NREL residential rooftop PV permitting guide makes the point clearly: AHJ requirements vary significantly across the 20,000-plus jurisdictions in the U.S. Your SLD needs to match what the reviewing AHJ expects, not just what the NEC requires in the abstract.

A few things worth confirming before you finalize the design:

• Which NEC edition the AHJ has adopted — this affects terminology, rapid shutdown documentation, and several conductor sizing references

• Whether the AHJ has a specific SLD format or checklist they want followed

• Whether the jurisdiction accepts SolarAPP+ compliant plan sets, which may streamline the submittal for qualifying residential jobs

• Whether a PE stamp is required on the electrical sheets — some AHJs require it for commercial jobs or systems above a certain size

California has additional requirements including CEC-listed equipment and in some cases Title 24 documentation that doesn't apply in other states. The IREC National Solar Licensing Database is a practical starting point for checking state-level requirements before you design.

Pre-Submittal Checklist: Solar One Line Diagram

Run through this before the permit package goes out.

DC side:

•  Max system voltage calculated with NEC 690.7 temperature correction

•  125% multiplier applied to Isc AND temperature correction and conduit fill derating applied

•  DC OCPD confirmed as DC-listed

•  Conductor insulation type called out for each circuit segment

Rapid shutdown:

•  Initiator location shown on the SLD

•  Compliance pathway documented

•  Label wording matches NEC 690.12(D) for the adopted code cycle

AC side:

•  AC OCPD sized at 125% of inverter continuous output current

•  Backfed breaker and busbar ratings shown and consistent with 120% rule (load-side jobs)

•  Interconnection method and applicable NEC section identified — 705.12(B) for load-side, 705.11 for supply-side

•  Service panel main breaker rating and busbar rating shown separately

Grounding:

•  EGC size shown per NEC 690.45 and 250.122

•  Grounding electrode system documented per NEC 690.47

Labels and service equipment:

•  Power source identification labels called out per NEC 690.56 and 705.10

•  Warning label language documented for service equipment

•  Utility-specific labeling requirements confirmed and included if applicable

General:

•  Equipment model numbers on SLD match cut sheets exactly

•  NEC edition in notes matches what the AHJ has adopted

If storage is in scope:

•  ESS shown as interactive source with its own disconnect and OCPD

•  Battery inverter listing information included

•  NEC 706 disconnect documentation reflected on the SLD

Let GreenLancer Build Your Next SLD

Getting every callout right on a solar one line diagram takes time — and a single missed derating factor or mismatched model number means a resubmittal. GreenLancer's permit design team produces complete, permit-ready plan sets with SLDs built to your AHJ's adopted code cycle. Whether it's a standard residential job or a solar plus storage submittal, we handle the documentation so you can stay focused on the field.

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FAQ: Solar One Line Diagram Requirements

What is a solar one line diagram?

A solar one line diagram is the electrical schematic of a PV system shown in simplified single-conductor notation. It's required in virtually every U.S. jurisdiction as part of the solar permit package and is the primary document plan reviewers use to verify NEC compliance.

What NEC sections govern solar SLD requirements?

NEC Article 690 is the primary reference, specifically sections 690.7 (maximum voltage), 690.8 (circuit sizing and the 125% multiplier), 690.9 (overcurrent protection), 690.12 (rapid shutdown), and 690.13 (disconnecting means). Article 705.12 governs load-side interconnection documentation on the AC side; Article 705.11 governs supply-side connections.

Why do solar one line diagrams get rejected at plan check?

The most common causes are missing temperature correction on the DC voltage calculation, conductor sizing that stops at the 125% multiplier without applying derating factors, DC OCPDs not confirmed as DC-listed, and equipment model numbers on the SLD that don't match the cut sheets.

Does a solar plus storage system need a different SLD?

Yes. The battery inverter must appear as an additional interactive source with its own OCPD, conductors, disconnect under NEC Article 706, and listing information. You cannot treat it as a load on the existing PV one line diagram.

Does the one line diagram need a PE stamp?

It depends on the AHJ. Most residential jurisdictions don't require a PE stamp on the electrical SLD for standard rooftop jobs. Some AHJs require a PE-stamped electrical review for commercial systems, complex interconnections, or service equipment modifications.

What changes on the SLD under NEC 2023?

The main changes affecting SLD documentation include updated terminology in Article 690, the NEC 690.7(D) requirement to mark maximum DC voltage in one of three specified locations, and 690.8 revisions around multiple PV string circuit sizing. Rapid shutdown label language and equipment method documentation also have 2023-specific requirements. See our 2023 NEC solar guide for a full overview.

What software do solar installers use to create one line diagrams?

Common platforms include Aurora Solar, SolarEdge Designer, Enphase Design Tools, HelioScope, and dedicated plan set tools. Some installers use AutoCAD or Visio for custom diagrams. Cloud-based solar design platforms generally produce cleaner, more consistent SLDs for permit submittal than general-purpose drafting tools. SolarAPP+ is a separate platform — it automates AHJ permitting and plan review but is not a design or drafting tool for creating SLDs.

Do all AHJs require the same solar one line diagram format?

No. Format requirements, required callouts, and acceptable drawing methods vary by jurisdiction. Some AHJs have proprietary forms or specific SLD templates. Confirm with the AHJ before finalizing your design, particularly when working in a new market.