THE SHORT ANSWER
OUC lists an electrical one-line diagram among required interconnection documents and says a professionally engineered PV design must carry the licensed engineer’s seal and signature. That final drawing is valuable evidence when the original installer is unavailable. [1]
Know what the drawing answers
A one-line diagram summarizes major electrical components and connections. It can identify the array, inverter, disconnects, service equipment and battery interface without requiring a new technician to infer the whole design from rooftop photos. It does not replace a site assessment, but it gives that assessment a reliable starting point.
Request the final, not a sales sketch
Look for a revision date, project address and equipment identifiers. Compare it with the passed permit and installed labels. An early proposal diagram may omit field changes, while a permit correction may be newer than the copy attached to the contract. Keep both only if their status is clearly labeled.
Recover records from more than one place
If the installer is closed, check the homeowner’s email, permit portal, utility interconnection packet, financing documents and equipment-owner account. Ask OUC what it can provide for the account; do not assume every utility record is a complete construction set. Follow the jurisdiction’s process for public permit records.
Use differences as questions
A replacement inverter, added battery or moved disconnect can make the old one-line inaccurate. Record the visible model information safely from the ground and accessible areas, without opening covers. Give the drawing and change history to the service provider so the quote can identify documentation work separately from physical repair.
Preserve the next revision
When service changes the system, ask who will update permits, utility records and the one-line when required. Store the closeout with monitoring access and warranty correspondence. Origin can review an orphaned OUC system, subject to equipment support and an accepted service scope.
Before your next conversation
- Search utility, permit and homeowner records for the final one-line.
- Match its equipment to accessible labels.
- Record later replacements or additions separately.
Primary sources
- OUC: Rooftop Solar and TruNet FAQs
Primary reference checked September 9, 2026. Confirm current requirements with the named utility, manufacturer or authority for your property.
Planning examples and questions are Origin’s editorial guidance, not a property-specific diagnosis, engineering design, tax determination or promise of savings. Manufacturer and utility references do not imply an affiliation with Origin.
Need help with the system you already have?
Attach the best available one-line and change history to an Origin maintenance request.
Request solar service →Equipment support, diagnostic fees, availability and accepted work are confirmed before service. A request is not a confirmed appointment.