one line diagram

Solar One Line Diagram 101: For Solar Contractors

In the world of solar PV installation, preparation is critical.

Whether the system is 5kW or 500kW – all solar contractors should undertake careful planning long before the installation takes place. Generating a solar one line diagram is a simple and effective way to design a solar system. It details the main components within the system and forms an integral part of the planning and approval process. It can be used by designers, installers, and even procurement and warehousing personnel. Whether the installation is simple or complex, a solar one-line diagram should be an essential part of every solar contractor’s process. It ensures that everything is documented in writing, helps to identify compatibility issues, and assures a more professional installation. As contractors take on projects of growing complexity, using one-line diagrams ensures that personnel are always working with the same core framework.

What Is a Solar One-Line Diagram?

A solar one line diagram (also known as a single line diagram) is an electrical drawing used to design a solar PV installation. A one-page document, it details the main components within the system and uses single lines to show how they are connected. The diagram also includes a summary of the wiring and electrical calculations. Diagrams should be presented in a format that is clean and simple to understand so that any person referencing the document can find information quickly and easily.

A one-line diagram ensures that all of the significant components and calculations are planned well in advance. This helps to identify any problems prior to installation, simplifies work for installation crews, and ensures that everyone is using the most current information.

These diagrams can also be requested by network operators for connection approvals. This is to ensure that the proposed installation meets all local electrical and engineering requirements.

What’s Included in a One-Line Diagram?

A one-line diagram provides a core breakdown of a solar PV design, presented in a straightforward, easy-to-digest format.

First and foremost, the diagram shows all the primary electrical components. This includes solar panels, inverters, disconnect switches, sub-panels, and junction boxes. The connections between them are then represented with simple lines. In a one-line diagram, a single line is drawn to connect components, regardless of the type of system. AC, DC, single-phase, and 3-phase are all represented in the same way. Panels and inverters are shown with simple square and rectangular shapes. Written next to these images can be model numbers, series connection figures, and basic wattage and amperage ratings.

The diagram also contains an equipment table. It details the make, model, quantity, and electrical ratings of the core equipment, including OCPDs. A further table includes a complete list of wiring calculations, such as voltage drop, amperage, and conduit ratings.

One-line diagrams can also contain summarized notes regarding critical equipment and safety information. This may include maximum DC voltages, breaker ratings, and grounding requirements specific to the installation.

Finally, the diagram should also list core information such as the client name and installation address, project ID, author, and date of issue. As one-line diagrams may be amended during the process, any version or revision numbers and dates should be clearly noted.

What Equipment Details Should Be Listed?

While one-line diagrams can vary in complexity, it is good practice to document as much useful information as possible. This forms a valuable ‘quick reference’ guide for everyone involved and ensures that all key electrical and equipment information is taken from the same source.

A summary of key equipment details can include:

Solar Panels (from the official datasheet)

  • Make and model
  • Quantity
  • PMAX
  • PTC
  • ISC
  • IMP
  • VOC
  • VMP
  • Temp. Coefficient of VOC
  • Fuse Rating

Inverters (from the official datasheet)

  • Make and model
  • Quantity
  • AC Voltage
  • Grounding
  • Max. OCPD Rating
  • Rated Power
  • Max. Output Current
  • Max. Input Current
  • Max. Input Voltage


  • Make and model
  • Quantity
  • Rated Current
  • Max. Rated Voltage


  • Quantity
  • Rated Current
  • Max. Voltage

With all core figures listed in a single source, this reduces any confusion or conflicts, as key information is taken directly from the manufacturer datasheets.

What Are the Benefits to Solar Contractors?

One-line diagrams help to simplify the entire solar installation process. They are an efficient way to plan all equipment in advance, identify issues, and create reference material for installers.

Depending on the size of the system and the requirements of the local network operator, and single-line diagram may be a compulsory part of the connection approval process. It may also be needed to meet the eligibility criteria of state rebates and incentives. Providing a detailed and accurate plan streamlines the approval process and avoids unnecessary delays. This is of benefit not just to solar contractors, but the end customer who receives a fast and efficient installation.

If you’re a solar contractor, a solar one line diagram should be a core component of every installation. In cooperation with a certified supply partner, you’ll have all of the needed documentation – and equipment – to complete every project efficiently and professionally.

Solerus Energy provides solar contractors with helpful information to help them save money on high-quality equipment and services. To learn more about solar one line diagrams and quality equipment at discount prices, feel free to contact us today!