Solar Interconnection Application:
Step-by-Step

What Is Interconnection and Why Does It Exist?

Interconnection is the utility's review and authorization process for connecting a customer-owned power-generating system — your solar panels — to the electric grid. It exists for two reasons: safety and grid stability. A solar system that isn't properly configured can create dangerous backfeed during a power outage, and thousands of small systems connecting without coordination can affect grid voltage and frequency.

The interconnection application is entirely separate from your building permit. The county permit authorizes the physical installation — the wiring, the racking, the electrical connections. The interconnection application authorizes your system to export power to the grid and receive net metering credits. You need both, and they run on separate timelines with separate agencies.

Who Submits the Interconnection Application?

In most cases, your solar installer submits the interconnection application on your behalf as part of their installation service. This is standard practice, and you should confirm this is included in your installation contract before signing. Ask specifically: "Will you handle the interconnection application with my utility?" and "Is that included in the price?"

However, as the account holder with your utility, you can also submit directly. Some homeowners prefer to do this to stay in control of the timeline. Either way, the application is filed under your utility account number — make sure your installer has your exact account number, not just your address, since utilities occasionally have multiple accounts at the same property.

The Full Interconnection Timeline

Total typical timeline: 25–60 business days from application submission to PTO, depending on your utility's workload. Submitting your interconnection application at the same time as your county permit application is the single most effective way to shorten this timeline — both reviews run in parallel instead of sequentially.

Step-by-Step: The Complete Interconnection Process

1. Confirm Your Electric Utility and Find Their Interconnection Program

   Your interconnection application goes to the utility that owns the meter at your property — not the state, not the county. Check your electric bill for the utility name, or look up your address on your state's utility commission website. Search "[utility name] distributed generation interconnection application" to find the current form and portal. Every utility has its own process — APS, SRP, PG&E, Duke Energy, and Xcel all use different portals and have different timelines.

2. Gather Your Required Documents

   Most utility interconnection applications require: your utility account number, a single-line electrical diagram (SLD) of the proposed system, equipment specification sheets (panels, inverter, racking), your county permit application number (not yet approved — submitted is usually sufficient), the proposed system size in kW DC and kW AC, and a signed interconnection agreement. Some utilities also require a site plan. Your installer should have all of these as part of their permit package.

3. Submit the Application Online (or by Mail)

   Most large investor-owned utilities (APS, SCE, Duke, Xcel, FPL) now have online portals for interconnection applications. Municipal utilities and electric cooperatives often still use paper forms or email submission. Pay any application fee at this step — fees range from $0 (many utilities) to $100+ for larger systems. Keep your application confirmation number: you'll need it to track status and correspond with the utility's interconnection team.

4. Application Completeness Review

   The utility reviews your submission for completeness — not technical approval, just whether all required fields and documents are present. If something is missing, they'll send a deficiency notice. Respond promptly: incomplete applications often reset the clock. This is where errors in your account number, equipment model numbers, or missing spec sheets will surface. Your installer should handle this, but staying in the loop on your application status is worth the effort.

5. Technical Review and Conditional Approval Letter (CAL)

   The utility's engineering team reviews your single-line diagram and equipment to confirm the system is technically compatible with their grid at your location. For most standard residential systems (under 10kW, with a UL-listed grid-tie inverter), this review is routine. The utility issues a Conditional Approval Letter (CAL) — sometimes called a "pre-approval" or "Preliminary Approval." This is not Permission to Operate. It means the utility has no technical objections and you can proceed with installation. Some utilities skip the CAL and go directly to final review after inspection.

6. Complete Installation and Pass County Final Inspection

   Your installer completes the installation. The county conducts and passes the final inspection. Your county's building department issues a Certificate of Completion or Certificate of Occupancy (CO/CC) — this document is what your utility needs next. Your installer should request this document from the AHJ and provide it to you and the utility. Don't skip this step: some utilities will not accept a copy of the inspection report pulled from the portal — they require the official certificate.

7. Submit the Final Inspection Report to Your Utility

   As soon as the county final inspection passes, submit the Certificate of Completion (or inspection record) to your utility's interconnection team. Use the same portal or contact method as your original application. Reference your application confirmation number. Some installers handle this automatically — ask in advance whether they will, or whether you need to submit it yourself.

8. Utility Meter Installation or Upgrade

   If your system requires a bidirectional net meter (needed to measure both energy consumed and energy exported), the utility schedules a meter technician visit. This is usually within 5–15 business days of receiving your inspection report. You do not need to be home in most cases — the utility technician can access the meter box from outside. However, if your meter is in an indoor enclosure, you'll need to arrange access.

9. Permission to Operate (PTO) Issued — System Goes Live

   After the meter is confirmed configured correctly, the utility issues Permission to Operate (PTO). This is typically a letter or email from the utility's interconnection department. Your installer can now energize the system fully. Do not turn the system on before receiving PTO in writing — doing so violates your interconnection agreement and can result in disconnection.

The Most Common Causes of Interconnection Delays

Interconnection delays are the most common complaint from solar customers — and most are avoidable. Here are the main culprits:

1. Submitting After Installation, Not Before

Waiting until the system is installed to submit the interconnection application adds 3–6 weeks to your total timeline. Submit simultaneously with your county permit application. Utilities allow pre-installation applications, and most technical review can complete before your installation even begins.

2. Account Number Errors

Using the wrong account number or service address causes the utility to be unable to pull your meter information, which stalls the technical review. Always use the exact account number from your current utility bill — not your auto-pay number or phone number.

3. Equipment Model Number Mismatches

If your installer substitutes equipment after the interconnection application is submitted (a common occurrence when supply chain issues arise), the utility application must be updated. Failing to update it causes a mismatch at final review, requiring a supplemental application and restarting the review clock.

4. Missing or Incorrect Single-Line Diagram

The SLD is the most technically scrutinized document in your application. Errors in conductor sizing, missing disconnects, or omitting rapid shutdown notation cause technical review rejection. Your installer's SLD should be prepared by someone familiar with your specific utility's requirements.

5. Utility Workload Peaks

Interconnection queues are longest in spring and summer when solar installations peak. Submitting in fall or winter can shave weeks off your wait. If you're in a high-growth solar market (Arizona, California, Florida, Texas), summer interconnection queues at major utilities can stretch to 45–60 days.

Interconnection by Major Utility

Electric Cooperative Interconnection — Different Rules

If your electricity is provided by a rural electric cooperative (co-op) rather than an investor-owned utility (IOU), the interconnection process may be significantly different. Co-ops are not subject to state utility commission rules in the same way IOUs are, which means their interconnection processes vary more widely.

Some key differences with co-op interconnection: paper-based applications are more common; timelines may be longer (30–60 days); physical inspection by the co-op may be required; anti-islanding relay requirements may be stricter; and net metering policies are often less favorable or absent. Contact your co-op's engineering or operations department — not the member services line — to get their specific interconnection requirements before your installer submits any documents.