Awaiting expert review. This page covers rules that vary by utility and jurisdiction. It is kept out of search results until a qualified reviewer has checked it; the sources below are dated so you can verify each point.
Quick answer
Solar Wiring is the full set of conductors, connectors, conduit, grounding and labels that carry power from solar panels to the inverter, the electrical panel and the grid. In the US its rules sit mainly in Article 690 of the National Electrical Code.
It covers both the DC side, from the panels, and the AC side, after the inverter. It is licensed electrical work. This page explains what is in it and what the code asks for, not how to install it.
Quick facts
The key facts about solar wiring, with sources:
- Main US code
- NFPA 70, the National Electrical Code (NEC), Article 690 1
- Wiring methods section
- NEC 690.31 (four parts in the 2023 edition) 1
- DC circuits inside buildings
- NEC 690.31(D): metal raceways and enclosures, plus marking 1
- Maximum DC voltage label
- New in the 2023 NEC: 690.7(D) 1
- Example PV wire standard
- UL 4703 Standard for Photovoltaic Wire 2
- Who may wire it in SC
- A licensed residential electrician or a qualified licensed contractor 5
Key takeaways
- Solar wiring is everything that carries power between the panels, inverter, home panel and grid.
- The NEC sets the rules in Article 690. Your state or city decides which edition is law.
- DC wiring inside a building must run in metal raceway under NEC 690.31(D).
- Outdoor panel-to-panel wiring uses sunlight-rated PV wire, such as cable listed to UL 4703.
- This is licensed work. Panels make voltage whenever light hits them.
More than wires: what “solar wiring” includes
People say "solar wiring" and picture the black cables under the panels. On a permit plan, it means much more.
It includes every conductor, the connectors that join them, the conduit that protects them, the grounding that keeps metal parts safe, the overcurrent devices, and the labels that tell an inspector or firefighter what is live.
How DC power behaves is on the direct current page. The roof shut-off rule is on the rapid shutdown page. This page sits between them. It covers the physical wiring system and the code sections that govern it.
The path power takes through the wiring
- Panel leads with connectors → join panels into strings on the roof or rack
- PV wire under the array → runs to a junction box or transition point
- Conductors in conduit → carry DC down the building to the inverter (string systems)
- AC conductors in conduit → run from the inverter through a disconnect
- Final connection → at the electrical panel or service, then the meter
DC circuits and AC circuits in one system
On a string inverter system, long DC runs go from the roof to the inverter on a wall. Those DC circuits can carry hundreds of volts. The 2023 NEC narrowed its Figure 690.1 to show only these DC PV circuits, which tells you where the code’s focus sits.
On a microinverter system, DC stays at each panel. The inverter under the panel turns it into AC right there. The Enphase IQ8 data sheet, for example, lists an adapter cable for MC4-type DC connectors and an AC output from each unit. So most of the run down the house is AC.
Both designs still need grounding, overcurrent protection, conduit where required and labels. What changes is how much high-voltage DC wiring runs across and into the building.
Parts of a solar wiring system
| Part | What it does | Code area (2023 NEC) |
|---|---|---|
| PV wire and panel leads | Outdoor, sun-exposed DC conductors | 690.31(C), single-conductor cable 1 |
| Connectors | Join panel leads and wires | Covered on our solar cable page |
| Junction or combiner box | Joins strings or changes wire type | 690.31 wiring methods |
| Conduit (raceway) | Protects wires; metal for DC inside buildings | 690.31(D)(1) 1 |
| Disconnects | Let equipment be isolated | 690.13 and 690.15 1 |
| Grounding and bonding | Keeps racking and frames at safe potential | 690.41–690.47 1 |
| Labels | Warn of DC, give the maximum voltage | 690.7(D), 690.31(D)(2) 1 |
Example: wiring lines you will find on a permit plan set
A typical residential plan set includes a single-line or three-line diagram. These are the wiring lines to look for. The right-hand column shows what each line tells you, with the code area it points to.
| Line on the plan | What it tells you | Code area |
|---|---|---|
| Conductor type and size for each run | Which wire is used on the roof, in conduit, and to the panel | 690.8 circuit sizing, 690.31 methods |
| Conduit type and route | Where DC enters the building and whether it is metal | 690.31(D) |
| Maximum DC system voltage | The number the installer must label | 690.7 and 690.7(D) |
| Disconnect locations | Where the system can be isolated | 690.13, 690.15 |
| Grounding electrode and bonding | How metal parts tie to earth | 690.41–690.47 |
| Rapid shutdown method | How roof wiring de-energises | 690.12 |
You do not need to check the math. You do want to see these lines exist, because an inspector reviews them. Ask your installer to walk you through the diagram. Our interconnection guide explains the paperwork around it.
Solar wiring compared with related terms
| Term | Focus | When to read it |
|---|---|---|
| Solar wiring | The whole conductor, conduit, grounding and label system | Understanding a plan set or inspection |
| Solar cable | The cable itself and its connectors | Checking PV wire types and connector matching |
| Direct current | How DC power behaves | Learning why DC needs special care |
| Rapid shutdown | NEC 690.12 voltage limits on roofs | Fire safety questions |
| Solar junction box | The box on the back of each panel | Hot spots and diode faults |
Where the wiring runs on a home
Under the panels. Leads and PV wire are clipped to the racking, off the roof surface. Loose, sagging wire is a red flag.
Through the roof or wall. Wires leave the array through a roof penetration or a side entry. Each roof penetration needs flashing to keep water out.
Down the house. Conduit runs to the inverter and disconnects. Inside a building, DC runs must be in metal raceway under 690.31(D). In an attic, that matters for fire safety.
At the panel. The AC connection lands at the main electrical panel or the service. Some homes need a panel upgrade first. The panel upgrade check helps you see if yours might.
What good wiring gets you, and what it costs in trade-offs
Benefits of code-compliant wiring
- Lower risk of arc faults and fires on the roof and in the attic.
- Passes inspection the first time, so permission to operate is not delayed.
- Clear labels help firefighters and future electricians.
- Less lost power in wire that is sized properly.
Trade-offs
- Metal conduit and longer runs add material and labour.
- Code rules change by edition, so an older design may need updates.
- More connection points mean more places a fault can start.
- Visible conduit on the outside of a home can look untidy.
Limits of what a homeowner can check
You can see if wires hang loose, if conduit is cracked or if labels are missing. You cannot see inside conduit, junction boxes or connectors without opening them, and you should not open them.
Wire sizing depends on current, temperature, distance and grouping. That is engineering work set by NEC 690.8 and the conductor tables. A homeowner check is a visual check only. For anything more, book a solar inspection.
What drives wiring cost on a quote
Wiring is rarely a separate line on a home quote. It is folded into the install price.
The drivers are the length of the run from array to inverter and panel, the conduit type (metal costs more and is required for DC inside buildings), how many roof faces the array spans, and whether the panel needs an upgrade.
Ground mounts often need a trench to the house, which adds work. Our solar cost guide and cost by system size show how these fit into the total. We do not print wire or conduit prices.
Lifespan depends on the cable’s rating and the install. The Southwire PV wire spec we read lists a continuous rating of 90°C in wet and dry locations and sunlight resistance. Ask for the wire spec sheet with your proposal.
How wiring gets designed, approved and inspected
This is the project path, not installation steps. A licensed electrician or installer does the work.
- The designer drafts a plan set with the wiring diagram, wire sizes and conduit routes.
- The installer submits it with the building or electrical permit.
- The permit office reviews it against the NEC edition it enforces.
- A licensed crew installs the wiring. In South Carolina, wiring and connection must be done by a licensed residential electrician or a qualified licensed contractor 5.
- An inspector checks wiring methods, grounding, labels and rapid shutdown on site.
- The utility approves the connection and grants permission to operate.
Keeping the wiring in good shape
Look, do not touch. From the ground, check for wires hanging below the array, chewed insulation, broken conduit straps and faded labels. Squirrels and other animals chewing cables is a known problem under arrays. Critter guards are an option to ask about.
After a storm, roof work or a panel removal and reinstall, ask the installer to re-inspect the wiring. A drop in production on your app can be an early sign of a wiring fault.
Warning signs and when to call a pro
Call your installer or a licensed electrician, and do not touch anything, if you see:
- A burning smell, scorch marks or melted plastic near any box or conduit.
- Wires hanging loose under the array or lying on the roof.
- Chewed insulation or nests under the panels.
- An arc-fault or ground-fault error on the inverter.
- Cracked or open conduit, or a junction box with a missing cover.
- Missing warning labels at the inverter, disconnects or service panel.
Safety rule
Solar wiring can stay live whenever light hits the panels, even with the main breaker off. Only a licensed electrician should open, move or repair it.
NEC Article 690 by edition
The code. The National Electrical Code is NFPA 70, published by the National Fire Protection Association on a three-year cycle. Article 690 covers solar PV systems. States and cities adopt an edition, sometimes with local changes, and that edition is the law where you live.
2023 edition changes. According to John Wiles’ March 2023 IAEI Magazine summary, the 2023 NEC split 690.31(A) wiring methods into four parts and expanded 690.31(B) on identifying and grouping conductors.
It removed the flexible wiring methods paragraph from 690.31(D), leaving (D)(1) on metal raceways and enclosures for DC circuits in buildings. It added 690.7(D), requiring the installer to mark the highest maximum DC voltage, and 690.31(G) for circuits over 1,000 V DC. It also moved definitions to Article 100.
South Carolina. A 2026 joint resolution, S.1077, would approve Building Codes Council Regulation Document 5418, which adopts the 2023 NEC. As of 16 April 2026 it was back in the Senate Labor, Commerce and Industry Committee. Until it passes, ask your permit office which edition it enforces.
Worker safety. OSHA says its electrical standards protect workers from electric shock, electrocution, fires and explosions. That is why roof and panel wiring is professional work.
Misconceptions about solar wiring
- Myth Turning off the main breaker makes the solar wires safe.
- Reality Panels still make DC voltage in light. Breakers isolate the AC side only.
- Myth Any outdoor wire can be used under panels.
- Reality Sun-exposed DC conductors need a cable type the code allows, such as PV wire listed to UL 4703 2.
- Myth Code rules are the same everywhere.
- Reality Each state or city adopts its own NEC edition and amendments.
- Myth Microinverter systems have no high-voltage DC wiring at all.
- Reality DC still runs from each panel to its microinverter, but runs are short. The long runs are AC 3.
Solar wiring rules in SC, GA and VA
In South Carolina, panel installers register with LLR as Residential Specialty contractors, and wiring and connection must be done by a licensed residential electrician, a Residential Builder, or a mechanical contractor with the electrical classification 5.
The move to the 2023 NEC was pending in S.1077 as of April 2026 4. We have not verified the NEC editions in force in Georgia or Virginia. Ask your county or city building department which edition applies before you sign.
When solar wiring matters to you
- You are comparing quotes and want to know where the conduit will run on your house.
- Your system failed inspection or shows fault codes.
- You are re-roofing and the panels and wiring must come off.
- You are buying a home with solar and want the wiring checked. See buying a house with solar.
Next steps
- Solar hazard checkSpot warning signs on an existing system
- Solar repairGet a licensed pro to look at a fault
- Verify an installer’s licenseCheck who will do the work
Questions about solar wiring
What code covers solar panel wiring?
The National Electrical Code, NFPA 70, Article 690. It covers wiring methods, circuit sizing, disconnects, grounding, labels and rapid shutdown for solar PV. Your state or city adopts a specific edition, sometimes with changes. The permit office can tell you which edition applies to your address.
Does solar wiring have to be in conduit?
Inside a building, DC solar circuits must run in metal raceway or metal enclosures under NEC 690.31(D) in the 2023 edition. Outdoors under the array, sunlight-rated PV wire may run without conduit where the code allows. Exact rules depend on your edition and the run, so the designer and inspector decide.
Can I wire my own solar panels?
We do not recommend it, and many places do not allow it. Solar wiring carries DC voltage whenever panels see light. In South Carolina, wiring and connection must be done by a licensed residential electrician or a qualified licensed contractor. A permit and inspection are also needed before the utility connects you.
What is PV wire?
PV wire is a single-conductor cable made for solar arrays. It is built to handle sunlight, heat and moisture outdoors. Southwire’s PV wire, for example, is listed to UL 4703, the standard for photovoltaic wire, and rated 2,000 volts and 90°C continuous. Our solar cable page compares it with other types.
What changed for solar wiring in the 2023 NEC?
IAEI’s summary lists several changes. The 2023 NEC split 690.31(A) wiring methods into four parts and kept 690.31(D) for metal raceways for DC inside buildings. It added 690.7(D), which makes the installer mark the highest DC voltage, and new rules for circuits over 1,000 V DC.
Why is there a warning label on my solar conduit?
The NEC requires DC circuits on or in buildings to be marked so electricians and firefighters know they may be live. Labels at the inverter, disconnects and service also show the maximum DC voltage and the rapid shutdown switch. Keep them clean and ask your installer to replace any that fade.
How do I know if my solar wiring is damaged?
Watch for loose wires under the array, chewed insulation, scorch marks, cracked conduit or a burning smell. An arc-fault or ground-fault code on the inverter is another sign. Do not touch anything. Call your installer or a licensed electrician to inspect it.
Is microinverter wiring safer than string inverter wiring?
It changes where the risk sits. Microinverters keep DC runs short at each panel and send AC down the house. String systems run higher DC voltage farther. Both must meet NEC 690, including rapid shutdown on buildings. Ask installers how their design handles roof and attic runs.
Does solar wiring need to be inspected?
Yes, where a permit is required, which is nearly everywhere for grid-tied systems. An inspector checks wiring methods, grounding, labels and rapid shutdown against the local code edition. The utility usually waits for a passed inspection before it gives permission to operate.
Sources
- IAEI Magazine (J. Wiles), 2023 National Electrical Code and Photovoltaic Power Systems, 23 March 2023, retrieved .
- Southwire, SPEC 45411: Copper 2000V XLPE RHH/RHW-2 Type PV cable (UL 4703, UL 44), retrieved .
- Enphase Energy, IQ8M and IQ8A Microinverters data sheet (DSH-00243-3.0-EN-2024-12-10), retrieved .
- South Carolina General Assembly, S.1077 (2025–2026), joint resolution approving Regulation Document 5418 (2023 NEC), retrieved .
- SC LLR, Residential Specialty Contractor registration (Solar Panel Installer) application package, retrieved .
- US OSHA, Electrical safety overview, retrieved .
Expert review
Written by the HyreSolar Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: NEC Article 690 changes from IAEI Magazine’s 2023 summary by John Wiles (the NEC text itself was not quoted).
Cable ratings from the Southwire SPEC 45411 page; microinverter wiring from the Enphase IQ8 data sheet; SC licensing from the LLR package as recorded in sc-local/facts.js; SC NEC status from the S.1077 bill page.
Held under G-REV until a licensed electrician reviews it. No installation steps are given.
Suggest a correction. We fix errors and say what changed.