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Solar panel wiring diagram explained: how a home rooftop system is connected

Published 16 Oct 2026 · Updated 16 Oct 2026

A homeowner's guide to a rooftop solar wiring diagram: strings, DCDB, ACDB, inverter, net meter, earthing and surge protection.

Most homeowners never see how their solar system is wired. The panels go up, a box appears on the wall, and the meter changes. But the wiring is where safety, reliability and long-term performance are decided. Knowing how a system is connected helps you understand your installer's design, ask the right questions, and spot shortcuts.

This guide explains a typical home rooftop wiring layout in plain language. It is for understanding, not for doing it yourself. Solar systems carry high DC voltages that can cause serious injury or fire. Wiring should be done only by qualified installers.

The big picture

A grid-connected home system has two sides:

  • The DC side: from the panels to the inverter. Panels produce direct current at a high voltage.
  • The AC side: from the inverter to your home's distribution board and the grid, via the net meter.

In between and around them sit the protection devices, earthing and the meter. Here is the flow in simple form:

Solar panels (in strings)
        |
   DC cables (in conduit)
        |
DC Distribution Box (DCDB)
  - DC isolator / breaker
  - DC fuses
  - DC surge protection (SPD)
        |
     Inverter
        |
AC Distribution Box (ACDB)
  - AC breaker / MCCB
  - AC surge protection (SPD)
        |
Net (bidirectional) meter
        |
Home distribution board  <-->  Grid (DISCOM)

Earthing:  frames, DCDB, ACDB, inverter  -->  equipment earth
Lightning arrestor  -->  separate dedicated earth pit

The rest of this guide explains each part.

1. The panels and strings

Solar panels are connected together in strings.

Series connection

In series, the positive terminal of one panel connects to the negative of the next. Voltages add up while the current stays the same. Most home systems connect panels in series to reach the voltage range the inverter needs.

Parallel connection

In parallel, positives connect together and negatives connect together. Currents add up while the voltage stays the same. Larger systems may have two or more strings, often connected to separate inverter inputs.

Why the arrangement matters

  • The string voltage must stay within the inverter's limits in every condition, including cool mornings, when panel voltage rises.
  • Panels in a string affect each other: shade on one can reduce the whole string's output.
  • Inverters with multiple MPPT inputs let strings on different roof sections work independently. See our inverter types guide.

Connectors

Panels connect using MC4 connectors. A poor or mismatched connector is one of the most common causes of faults and even fires in solar systems. We use Stäubli-grade MC4 connectors on every DC connection.

2. DC cables and conduits

DC cables carry power from the strings down to the inverter. They must be:

  • solar-rated: built for UV exposure, heat and long outdoor life;
  • correctly sized: undersized cables lose energy and can overheat. Our standard is 4 sqmm DC cable;
  • protected: run in conduits to shield them from sun, rain and rodents. We use UPVC conduits over every cable run;
  • neatly routed and secured, without sharp bends or strain on connectors.

3. The DC Distribution Box (DCDB)

The DCDB sits between the panels and the inverter. It typically contains:

  • a DC isolator or breaker, to safely disconnect the panels from the inverter for maintenance;
  • DC fuses, to protect strings from fault currents;
  • a DC surge protection device (SPD), to protect against voltage surges, including those caused by nearby lightning.

We use Siemens or Finder DCDB and ACDB enclosures.

4. The inverter

The inverter converts DC to AC, tracks the panels' maximum power point and synchronises with the grid. It should be mounted:

  • in shade, with good ventilation (heat shortens inverter life);
  • at a height that is easy to read and service;
  • away from water and direct rain.

In a hybrid system, the inverter also connects to a battery bank, with its own fuse and isolation between battery and inverter. See our hybrid inverter guide.

5. The AC Distribution Box (ACDB)

The ACDB sits between the inverter and your home's supply. It typically contains:

  • an AC breaker or MCCB, to protect and isolate the inverter's output. Our standard includes a 25A MCCB;
  • an AC surge protection device (SPD);
  • connection to the home's distribution board.

AC cable from the inverter to the ACDB and onward must be correctly sized for the system's current; our standard is 4 sqmm 2-core AC cable.

6. The net meter

For a grid-connected system with net metering, the DISCOM installs or approves a bidirectional meter. It records units imported from the grid and units exported to it separately. The net meter is part of the DISCOM approval process, which includes a feasibility application and an inspection. At Origian, the net metering application and DISCOM coordination are part of the installation. Our guide to import and export units explains how to read the meter.

7. Earthing: the part you must not skip

Earthing gives fault currents and surges a safe path to the ground. A rooftop system is a large metal structure on the highest point of the building, so earthing is essential.

A proper system has:

  • equipment earthing, bonding every panel frame, the mounting structure, the DCDB, the ACDB and the inverter to earth. We use 6 sqmm copper earth cable, with 80 metres of it bonding every frame, enclosure and the inverter;
  • a dedicated lightning-arrestor earth, in its own separate pit, not shared with the equipment earth.

Our guide to solar earthing and lightning protection explains why the separate pit matters.

8. Surge protection on both sides

Surges can come from lightning, grid switching or faults. Protecting only one side leaves the other exposed. A good design includes surge protection devices on both the DC and AC sides, as we install on every system.

Single-phase and three-phase connections

The AC side connects to your home's supply, which may be single-phase or three-phase. The inverter must match. In three-phase homes and businesses, the design also needs to consider how the solar output is balanced across phases. Your installer should check the connection type and sanctioned load during the site visit.

Common wiring mistakes we see on other systems

When we inspect existing systems, these are the problems that come up most:

  • cheap or mismatched MC4 connectors, sometimes taped together;
  • undersized cables, warm to the touch in operation;
  • cables lying exposed on the roof without conduit, cracked by sun or chewed by rodents;
  • no DC isolator, making safe maintenance difficult;
  • missing surge protection, or SPDs on one side only;
  • panel frames not earthed, or earth shared with the lightning arrestor;
  • the inverter mounted in direct sun.

Each of these can reduce output, shorten equipment life or create a safety risk.

What to check in your installer's design

Ask for a single-line diagram (SLD) of your system before installation. It should show:

  1. The number of panels, how they are arranged in strings, and string voltages.
  2. The cable sizes on the DC and AC sides.
  3. The DCDB contents: isolator, fuses, SPD.
  4. The ACDB contents: breaker or MCCB, SPD.
  5. The inverter model and its inputs.
  6. The earthing arrangement, including a separate lightning-arrestor earth pit.
  7. Where the system connects to your home supply and the net meter.

If an installer cannot show you a clear design, treat that as a warning.

Safety for homeowners

  • Do not open the DCDB, ACDB or inverter. DC voltage remains present whenever the panels see light, even if the inverter is off.
  • Do not disconnect MC4 connectors under load. This can cause dangerous arcing.
  • Know where the isolators are and how to switch off safely in an emergency; your installer should show you.
  • Report warm cables, burning smells, buzzing or scorch marks immediately.
  • Keep children away from the equipment.

How Origian wires every system

Every system we install follows the same specification:

  • Stäubli-grade MC4 connectors on every DC connection, and pin-type lugs on all MCB connections;
  • Polycab (or equivalent) cable: 4 sqmm DC, 4 sqmm 2-core AC, 6 sqmm copper earth;
  • UPVC conduits over every cable run;
  • Siemens or Finder DCDB and ACDB, with a 25A MCCB;
  • surge protection on both DC and AC sides;
  • equipment earthing bonding every frame, enclosure and the inverter, plus a dedicated lightning-arrestor earth pit;
  • heat-shrink sealing on cable ends and sealant at every roof penetration.

Our Built to Last page shows the hardware in more detail. For a system designed this way on your roof, book a free site survey.

Hybrid and off-grid wiring: what is different

The diagram above is for a grid-connected (on-grid) system. Hybrid and off-grid systems add a battery side:

Solar panels  ->  DCDB  ->  Hybrid inverter  <->  Battery bank
                                   |                (fuse + isolator)
                                 ACDB
                                   |
                     Backup (essential loads) circuit
                                   |
                 Net meter  <->  Grid  (hybrid only)

Key additions:

  • battery cables sized for high current, with a fuse and isolator between battery and inverter;
  • a separate backup circuit for essential loads that stay powered during outages;
  • changeover arrangements so the inverter isolates the home from the grid during an outage, for line workers' safety;
  • battery placement in a shaded, ventilated space.

In off-grid systems there is no grid connection or net meter at all; everything runs from panels and batteries. See our hybrid inverter guide.

Cable sizing in plain words

Every cable has a resistance. Current flowing through it loses some energy as heat. A cable that is too thin for the current:

  • wastes more energy, reducing the units you get;
  • runs hotter, ageing its insulation faster;
  • in the worst cases, becomes a fire risk.

Correct sizing depends on the current, the length of the run and the installation conditions. Long cable runs, from a large roof to a basement meter room for example, may need thicker cable to keep losses low. Our standard specification uses 4 sqmm DC cable, 4 sqmm 2-core AC cable and 6 sqmm copper earth cable, sized for typical home systems. Larger or longer runs are sized individually.

Labelling and documentation

A well-installed system is labelled so anyone working on it later knows what they are looking at:

  • DC isolators and AC breakers clearly marked;
  • warning labels on DC equipment that stays live in daylight;
  • the system's single-line diagram kept with the home's documents.

Good labelling makes maintenance safer and faster, and helps emergency services if they ever need to isolate the system.

Testing before switch-on

Before a system is commissioned, a careful installer checks:

  • each string's open-circuit voltage, to confirm the panels and connections are correct;
  • polarity, so positive and negative are not reversed;
  • insulation resistance, to find damaged cables;
  • earth continuity across frames and enclosures;
  • that breakers, isolators and SPDs are correctly installed;
  • inverter settings for the grid and, for hybrid systems, the battery.

Ask your installer what tests they do before switch-on, and whether they record the results.

Reading a single-line diagram (SLD)

Installers often present the wiring as a single-line diagram, or SLD. It is a simplified drawing that shows how power flows, using one line to represent each circuit. A typical rooftop SLD, read from left to right:

  1. PV array: boxes for each string of panels, with the number of panels and their rating.
  2. DCDB: a box showing DC isolators, fuses (where used) and DC surge protection devices.
  3. Inverter: with its rating and number of MPPT inputs.
  4. ACDB: showing the MCCB or MCB, AC surge protection and isolator.
  5. Net meter: the point where the system connects to the grid.
  6. Earthing: symbols showing earth connections, and the lightning arrestor with its own separate earth.

You do not need to read every symbol. But you should be able to see that both DCDB and ACDB are present, that surge protection appears on both sides, and that the lightning arrestor has its own earth. If any of these is missing from the diagram, ask why.

String voltage and the inverter window

Each inverter has an MPPT voltage range, the range within which it can harvest power efficiently, and a maximum input voltage it must never exceed.

Panels connected in series add their voltages. The designer must choose the number of panels in each string so that:

  • on a hot afternoon, when panel voltage falls, the string voltage stays above the inverter's lower MPPT limit;
  • on a cool, bright morning, when panel voltage rises, it stays below the inverter's maximum input voltage.

This is why string design is engineering, not guesswork. A string that is too long can damage an inverter on a cold winter morning; one that is too short wastes power on hot afternoons.

Why DC wiring needs particular care

DC from solar panels behaves differently from household AC:

  • it is present whenever there is light, even when the inverter is switched off;
  • DC arcs are harder to extinguish than AC arcs, so a loose connection can sustain an arc and overheat;
  • string voltages can be several hundred volts, well above household AC.

That is why DC wiring needs solar-rated cable, quality MC4 connectors that are correctly crimped and fully mated, protective conduit, and DC-rated isolators. It is also why homeowners should never open the DCDB or disconnect panel connectors.

Upgrading or extending a system later

If you plan to add panels later, tell your installer at the start. Extending a system may need:

  • a larger inverter, or spare MPPT capacity on the existing one;
  • additional DCDB capacity;
  • larger AC cabling and breakers;
  • a revised net metering approval with the DISCOM.

Planning for future expansion during the first design can save significant rework later.

Frequently asked questions

What is a solar panel wiring diagram? A solar panel wiring diagram shows how a rooftop system connects: panels in strings, DC cables to the DC distribution box, the inverter, the AC distribution box, the net meter and the earthing. Installers often draw it as a single-line diagram; ask for one and check that protection appears on both sides.

Should solar panels be connected in series or parallel? Most rooftop solar panels are connected in series to form strings, adding voltage to suit the inverter's MPPT range; strings may then run in parallel or to separate MPPT inputs. The right arrangement depends on panel and inverter specifications, temperature and shade, so it is an engineering decision, not a guess.

What is a DCDB and ACDB in a solar system? In a solar system, the DCDB (DC distribution box) protects and isolates the panel side before the inverter, with isolators, fuses where needed and surge protection. The ACDB protects the inverter output before your home's supply, with a breaker, surge protection and an isolator. Origian uses Siemens or Finder boxes.

What size cable is used for rooftop solar wiring? Rooftop solar cable size depends on the current, run length and acceptable voltage drop. On Origian systems we use Polycab or equivalent 4 sqmm solar DC cable and 4 sqmm 2-core AC cable, run in UPVC conduit, with Stäubli-grade MC4 connectors. Undersized cable wastes energy as heat and can be a fire risk.

Is solar DC wiring dangerous? It can be. Solar DC is live whenever there is light, even with the inverter switched off; string voltages can reach several hundred volts; and DC arcs are harder to extinguish than AC arcs. That is why solar DC wiring needs rated cable, proper connectors and isolators, and homeowners should never open the DCDB.

Can I extend my rooftop solar system later? Often, yes, but plan it. Extending a rooftop solar system may need a larger inverter or spare MPPT capacity, more DCDB and ACDB capacity, larger AC cable and breakers, and a revised DISCOM approval. Mention any future plans when the system is first designed to avoid costly rework later.

What is the difference between single-phase and three-phase solar connection? A single-phase solar connection uses a single-phase inverter feeding one phase of your supply, which is common for smaller homes. A three-phase solar connection uses a three-phase inverter that balances output across all three phases, common for larger homes and businesses. Your connection type and system size decide which you need.

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