Quick answer
A simplified schematic of electrical equipment and connections using single-line power paths. Solar drawing content depends on project scope, authority and utility requirements; it is not a physical routing plan.
What Is an Electrical SLD?
Answer: An electrical single-line diagram, or SLD, summarizes a power system’s equipment and connections using simplified lines and symbols. In solar, it can show the PV source, conversion equipment, protection, metering and connection to the building or grid. It communicates electrical topology, not physical cable routing. Required details and acceptance depend on the project, permitting authority and utility.
A one-line diagram uses a simplified representation rather than drawing every phase conductor individually. The Engineering Institute of Technology’s electrical-drawings guide distinguishes single-line, three-line, cabling and terminal drawings. A three-line diagram can expand phase-level connections; neither drawing title guarantees that all installation details are present.
An SLD supports review, but it does not by itself prove code compliance, compatible equipment or an approved installation. Keep it consistent with the other electrical line diagrams, equipment documents and relevant calculations.
What a Solar SLD Can Show
Use the actual project scope and submission checklist to determine the content. The following categories are review prompts, not a universal drawing standard:
| System element | Information to reconcile |
|---|---|
| PV modules and arrays | Selected model, quantity, electrical configuration and relevant ratings |
| DC equipment | Applicable combining, protection, isolation and connection arrangements |
| Inverters or other conversion equipment | Exact model, rating, input/output arrangement and relevant phases |
| AC equipment | Distribution, disconnects and protective devices within the defined scope |
| Conductors and containment | Required sizes, types, counts and references to the actual design |
| Grounding and bonding | Applicable arrangement and references to detailed drawings |
| Metering and connection | Required meters, service equipment and defined interconnection point |
| Control or shutdown functions | Relevant devices, boundaries and references to separate details |
Not every system has string fuses, a combiner box, a production meter or the same shutdown architecture. Do not add equipment to a diagram just because it appears in a template. Clearly identify new, existing and removed equipment where that distinction matters.
Residential, Commercial and Storage Contexts
Residential: show the selected inverter architecture and actual connection to existing service equipment. A microinverter arrangement and a DC string-inverter arrangement have different topology; do not substitute one generic template for both.
Commercial or larger projects: include the actual multiple-inverter, distribution, transformer, metering or protection arrangement where applicable. The necessary detail is not established by an arbitrary 25 kW threshold.
Storage: distinguish AC-coupled and DC-coupled arrangements, supported modes and the exact isolation/transfer equipment. A battery symbol alone does not establish backup operation, neutral switching, grounding or authorization to island.
Utility interconnection: confirm the serving utility’s own application requirements. Its drawing review can have a different scope from the local permit package.
As a specific reference, Portland General Electric’s August 2024 Distribution Interconnection Handbook, section 12, supplies example SLDs and identifies them as illustrative. Applicants need project-specific drawings consistent with that utility’s requirements. This is not Pacific Gas and Electric, and it is not a nationwide template or proof of the latest requirements for a particular application.
Review the Drawing Against Its Evidence
- Identify the revision and scope. Include a clear project reference, drawing identifier, revision, legend and the intended submission or release purpose.
- Trace the electrical arrangement. Confirm that sources, conversion equipment and connection points match the released design. Resolve omitted or contradictory branches.
- Reconcile ratings and configuration. Match equipment identifiers and relevant data to exact product documents. An ampere rating, interrupting rating and equipment short-circuit rating describe different things.
- Check calculations and detail references. Required conductor, protection, bus, grounding and operating checks need their actual applicable method and inputs. The SLD can summarize a calculation without replacing it.
- Cross-check the other documents. Compare layout, string assignments, routing, equipment schedules and any three-line or terminal drawings. A topology line does not establish route length.
- Resolve findings before the applicable release. Use the design review workflow to identify the reviewer, unresolved matters and disposition.
Do not assume a simplified “120% bus rule” applies to every connection method, or that a generic rapid-shutdown note establishes exact system compliance. Have the responsible professional verify the applicable code edition, configuration, instructions and calculations. This page is not a conductor-sizing or live-work procedure.
Drawing, Approval and Installed Record
Designers: use a clear documented symbol convention and legend. Automated output still needs equipment, ratings and cross-document review; a software-generated drawing is not automatically accepted by an authority.
Installers: confirm the current approved/released drawing set and equipment configuration. Use the applicable installation and terminal documents as well as the SLD. Route field changes through required review rather than treating a markup as approval.
Sales and project managers: explain which drawings and reviews the agreed deliverable includes. Do not promise zero corrections, universal review times or approval on the first submission because an SLD was produced.
At handoff, reconcile accepted installed changes with as-built drawings. Keep local permit acceptance and utility operating authorization separate from the internal drawing release.
Book a SurgePV demo with the actual schematic and export requirements your project needs. Verify demonstrated drawing coverage and the remaining engineering and review responsibilities.
Frequently Asked Questions
How does an SLD differ from a three-line diagram?
An SLD summarizes the system with simplified power paths. A three-line diagram expands phase-level electrical connections. Required neutral, grounding, terminal or control details depend on the drawing scope and configuration.
Does an SLD show physical cable routing?
Not normally. It communicates electrical relationships. Use the relevant routing, installation and terminal drawings to identify physical paths and connections.
What must be included for a solar permit?
Check the actual authority and utility submission requirements. Match the drawing to project equipment, calculations and applicable details rather than assuming one universal template or equipment-size threshold.
Does an automatically generated SLD guarantee approval?
No. Inputs, equipment configuration, local requirements and relevant calculations still need review. Drawing generation, professional release, authority acceptance and utility authorization are distinct.
Related Glossary Terms
About the Contributors
Editorial contributor · SurgePV
Rainer Neumann is credited as an editorial contributor on SurgePV content. This profile does not assert engineering credentials, project totals, software-testing experience, education, speaking engagements, or media citations because independent verification evidence is not retained in the publication record.
CEO & Co-Founder · SurgePV
Keyur Rakholiya is identified by SurgePV as its CEO and a company co-founder. His SurgePV author page lists only role information that can be tied to the public profile below; credentials, project totals, testing claims, media appearances, and speaking engagements are not asserted without retained evidence.
