Solar Electrical Design Services and Single-Line Diagrams

The electrical design is the technical heart of every solar PV project and the section AHJs and utilities scrutinize most closely. Incomplete or non-compliant single-line diagrams (SLDs) are the number one cause of solar permit rejection in the US. RIH Engineering delivers solar electrical design services, including SLDs formatted to every major US utility, three-line diagrams, conductor sizing, and full protection coordination, as an outsourced electrical design partner for US solar EPCs, installers, and developers.

What you get

• Solar single-line diagrams (SLDs) formatted per specific utility conventions (PSE&G, ConEd, PG&E, LADWP, SDG&E, APS, SRP, Xcel, Eversource, National Grid, and all others)
• Three-line diagrams for AHJs and utilities that require them
• Conductor sizing per NEC 310.15 including ambient temperature derating and conduit fill
• Voltage drop calculations for all runs
• Overcurrent protection sizing and coordination
• Grounding and bonding design per NEC 690.41 through 690.50
• Rapid shutdown design per NEC 690.12 with compliant equipment specification
• Panel schedules, load calculations, and interconnection point details
• Label and signage details per NEC 690, 705, 706, and 710

What we handle for you

Solar electrical design is precise, code-heavy work. Every SLD requires familiarity with the specific utility's formatting conventions, the AHJ's adopted NEC edition, the equipment being installed, and the applicable protection coordination requirements. Doing this in-house means either a full-time electrical engineer or your senior team spending 4 to 12 hours per project on drawings AHJ inspectors will scrutinize line by line.

We take electrical design off your plate. You send us the project details, equipment selection, utility, and AHJ. We come back with utility-formatted SLDs, three-line diagrams, conductor sizing calculations, protection coordination, and all required electrical documentation, formatted for first-submission approval.

The cost of doing this in-house

Every solar company we work with has, at some point, had a project delayed 2 to 6 weeks because of electrical design rejections. Wrong SLD format for the utility. Incorrect conductor sizing. Missing rapid shutdown documentation. Inadequate protection coordination. Each rejection means a revision cycle. Each revision cycle means the installer waits, the customer's patience erodes, and your project pipeline stalls.

The cost of getting electrical design wrong exceeds the cost of getting it right by an order of magnitude. Rejected permit revisions cost time, damage AHJ relationships, and force your senior engineers to rework designs they should have done right the first time. Outsourcing to a specialist who knows every utility's SLD format eliminates this cost entirely.

Why RIH Engineering is safe to try

Send us one project. We deliver electrical design in 3 to 7 days depending on complexity. You compare the SLD, three-line, conductor sizing, and protection coordination against your standards. If quality doesn't meet your bar, we adjust. If it still doesn't work, you don't send us the next project.

Our team has produced SLDs for every major US utility interconnection format. We maintain current templates for each utility's specific conventions and update them as utilities revise their standards. This is exactly the kind of specialized knowledge that's expensive to maintain in-house but cheap to access through an outsourced partner.

Our process

1. You send us project details, equipment selection (modules, inverters, disconnects, protection), utility, and AHJ
2. Our electrical engineer verifies utility SLD format and AHJ NEC edition
3. SLD drafted per utility conventions with all required equipment, conductors, protection devices, and disconnects
4. Conductor sizing calculated per NEC 310.15 with ambient temperature derating and conduit fill
5. Voltage drop verified for all runs
6. Overcurrent protection sized and coordination verified
7. Grounding and bonding designed per NEC 690.41 through 690.50
8. Rapid shutdown design documented per NEC 690.12 with UL PVRSS listed equipment
9. Deliverables sent for your review, typically within 3 to 7 days

Tools and standards

Our electrical design team works in AutoCAD, AutoCAD Electrical, Revit, and utility-specific SLD templates for every major US investor-owned utility and cooperative. We maintain current templates for PSE&G, ConEd, PG&E, LADWP, SDG&E, APS, SRP, Xcel, Eversource, National Grid, ComEd, Duke Energy, FPL, Georgia Power, and others.

Client-preferred tools: Our team can be trained to use the tool preferred by the client. If your workflow depends on a specific platform, template, or drafting standard, we adapt to it rather than force you into ours.