SDG&E Interconnection for Commercial Solar: What to Expect and What Can Go Wrong

Most commercial solar proposals focus on system size, production estimates, and financial returns. Very few give a clear, honest account of the interconnection process — the series of applications, reviews, and approvals that SDG&E must complete before a solar system can legally export power to the grid. For San Diego commercial property owners, interconnection is often the longest and least predictable part of a solar project, and the timeline assumptions in most proposals do not reflect how the process actually works.

What the SDG&E Interconnection Process Actually Involves

Connecting a commercial solar system to the SDG&E grid requires an interconnection application submitted by the installer on behalf of the property owner. SDG&E reviews the application to determine whether the proposed system can be connected to the local distribution grid without requiring upgrades to transformers, conductors, or other infrastructure. For smaller commercial systems on circuits with available capacity, this review is relatively straightforward. For larger systems, or systems on circuits that are already heavily loaded, the review can require a more detailed technical study — and potentially require the property owner to fund grid upgrades before the system can be approved.

The interconnection application is separate from the building permit, the NEM application, and the final inspection. Each step has its own timeline, and delays at any one of them can push back the date when the system receives permission to operate — the point at which it can legally turn on and begin generating bill credits.

Where Timelines Slip — and Why Proposals Often Understate Them

Installer proposals routinely show project timelines of three to six months from contract signing to permission to operate. For straightforward residential systems, that range can be accurate. For commercial systems — which are larger, more complex, and subject to more detailed utility review — the actual timeline is frequently longer, and the variables that extend it are largely outside the installer's control.

Common sources of delay include:

• Supplemental review: If SDG&E's initial screen identifies potential grid capacity issues, the application moves to a more detailed study process that adds weeks or months to the timeline.
• Grid upgrade requirements: If the study identifies required upgrades, the property owner must decide whether to fund them, negotiate cost allocation, or redesign the system to reduce its export capacity — each of which takes time.
• Incomplete applications: Interconnection applications that are missing documentation or contain errors are rejected and must be resubmitted, restarting the review clock.
• Permit coordination: Building permits and interconnection approvals must both be in place before installation can begin. Delays in either process hold up the other.
• Inspection scheduling: Final utility inspection — required before permission to operate is granted — can add additional weeks depending on SDG&E's scheduling queue at the time of completion.

A proposal that shows a six-month timeline without disclosing these variables is not necessarily dishonest — but it is optimistic in a way that can create real problems for a property owner who has made financial plans based on a specific in-service date.

What to Ask Before Signing a Contract

Before committing to a commercial solar project in San Diego, several interconnection-related questions are worth asking independently:

• Has the installer checked the available capacity on the circuit serving the property, and does the proposed system size fit within that capacity?
• What is the installer's experience with SDG&E interconnection applications for commercial systems of this size, and what is their typical timeline from application submission to approval?
• Does the contract include any provisions if interconnection is delayed beyond the projected timeline — and who bears the cost if grid upgrades are required?
• Is the financial model in the proposal based on a specific in-service date, and what happens to the projected returns if that date slips by three to six months?

Solar Power San Diego reviews commercial solar proposals for San Diego property owners as an independent advisor — with no installer commissions and no financial interest in which project moves forward. We examine the interconnection assumptions in proposals, identify where timelines are optimistic, and give property owners a clear picture of what the process actually involves before they sign a contract.