Grid Interconnection Application

A Grid Interconnection Application is the formal process a solar installer, EPC, or developer must complete to request permission from the utility company to connect a solar PV system to the electrical grid. This application ensures the system is reviewed for safety, capacity, compliance, and grid stability before construction or commissioning.

For residential and commercial solar projects, the interconnection application is one of the most important—and often most time-consuming—steps in the project lifecycle. It involves submitting technical documentation, system specifications, line diagrams, load calculations, and equipment details. Modern solar platforms such as Solar Designing help designers prepare accurate and code-compliant documentation used during this process.

The outcome of a grid interconnection application determines whether a project receives approval, requires upgrades, or needs further engineering review.

Key Takeaways

A Grid Interconnection Application is required for any solar PV system connecting to the electrical grid.
It includes electrical diagrams, system data, layout plans, equipment certifications, and engineering details.
Utilities review applications for safety, voltage stability, transformer loading, and compliance.
Approval may be simple (fast-track) or complex (supplemental review or full grid study).
Accurate designs and engineering documentation speed up approval and reduce project delays.

What Is a Grid Interconnection Application?

A Grid Interconnection Application is the package of forms, designs, and technical documents submitted to a utility to request connection of a solar PV system to the electricity grid. Depending on the jurisdiction, this may be known as:

Interconnection Request (IR)
Net Metering Application
Distributed Energy Resource (DER) Interconnection
Grid-Tie Approval Request
Utility Interconnection Permit

The application typically includes electrical diagrams, project details, equipment specs, inverter data, safety requirements, and expected energy export.

How the Grid Interconnection Application Process Works

While each jurisdiction and utility has unique requirements, most interconnection processes follow these steps:

1. Preliminary Project Assessment

The designer confirms system size, grid type, available service, and any local rules.

Tools such as Solar Designing help ensure accurate sizing before paperwork begins.

2. Prepare Required Documentation

Typically includes:

Electrical Single-Line Diagram (SLD)
System layout and module placement
Equipment datasheets
Inverter certifications
Load calculations
Proposed AC interconnection point
Site plan showing meter and service panel

Related: Electrical Line Diagrams

3. Submit the Interconnection Application to the Utility

Submission may be online, emailed, or via paper forms depending on the utility.

4. Utility Engineering Review

Utility engineers evaluate:

Grid capacity
Voltage fluctuations
Reverse power flow
Protection equipment
Safety and anti-islanding requirements

5. Conditional Approval, Further Review, or Upgrade Requirement

Outcomes may include:

Approval — project can proceed
Supplemental review — more engineering analysis needed
Required upgrades — transformer, service panel, or feeder improvements
Rejection — system cannot connect in current form

6. Permission to Construct (PTC)

Once approved, installation can begin.

7. Post-Construction Documentation

As-built drawings, inspection reports, inverter settings, and photos.

8. Permission to Operate (PTO)

After final utility inspection, the system is allowed to operate and export electricity.

See: O&M Management for post-commissioning considerations.

Types / Variants of Interconnection Applications

1. Simplified / Fast-Track Interconnection

Used for small residential systems that fall below certain thresholds (often < 10 kW).

These require minimal engineering review.

2. Standard Interconnection Review

Used for most commercial and larger residential systems.

Includes a detailed utility engineering analysis.

3. Supplemental Engineering Review (SER)

Additional study required when system exports could affect:

Voltage regulation
Feeder loading
Transformer limits
Fault current

4. Utility-Scale Interconnection Request

Involves extensive modeling, power flow studies, and grid-impact analysis for large DER projects.

5. Net Metering Application

A simplified version of interconnection tied specifically to programs that credit solar exports.

How It’s Measured

Grid interconnection applications are evaluated using criteria such as:

System Size (kW / MW)

Total AC rating of the solar system.

Export Capacity

How much energy the system will send back to the grid.

Transformer Loading

Measured in percentage of rated capacity.

Fault Current Contribution

Critical for grid protection coordination.

Voltage Rise

Determined by AC run length, conductor size, and load conditions.

Use the Voltage Drop Calculator to support this step.

Typical Values / Ranges

These timelines vary widely by utility and local regulations.

Practical Guidance for Solar Designers & Installers

1. Submit accurate electrical diagrams

Use tools like Solar Designing to ensure inverter placement and AC interconnection points are correct.

2. Understand utility-specific requirements

Each utility uses unique thresholds and forms—prepare documentation accordingly.

3. Avoid voltage rise issues

Plan AC conductor lengths carefully using the Voltage Drop Calculator.

4. Use certified equipment only

Utilities require UL-listed inverters, rapid shutdown devices, and compliant BOS components.

5. Prepare for possible upgrades

Transformers, meters, and service panels often require updates.

6. Maintain clear communication with the utility

Follow up on application status to avoid project delays.

7. Submit clean, professional documentation

Use the Solar Project Planning Hub to prepare plan sets and submission packages.

Real-World Examples

1. Residential Grid Interconnection (Fast-Track)

A 6 kW system meets all simplified interconnection criteria.

The utility approves the application in 48 hours, and installation proceeds immediately.

2. Commercial 250 kW Rooftop System

The application triggers a supplemental engineering review due to feeder load limits.

The utility requires a transformer upgrade before approval.

3. Utility-Scale Solar Farm

A 20 MW project submits an interconnection request that requires multiple power flow studies.

Approval takes 14 months and includes protective relay coordination.