Utility interconnection is the process of obtaining permission to connect a solar energy system to the electric grid. It can affect project design, cost, schedule and financial viability, making it one of the most important workstreams in solar development.
This guide introduces the major stages of the commercial solar interconnection process and explains how to use The Energy Academy’s interactive roadmap to explore them.
Open the Interactive Interconnection Roadmap
What Is Solar Interconnection?
Interconnection is the technical and administrative process used by a utility or grid operator to evaluate whether and under what conditions a proposed energy system may connect to the electric grid.
The process is intended to confirm that the system can operate safely and reliably without creating unacceptable impacts on the distribution or transmission system.
Requirements vary by utility, jurisdiction, project size, technology and whether the system will export electricity to the grid.
Why Interconnection Matters
A project may have a willing customer, site control and attractive economics but still face major challenges if the grid cannot accommodate the proposed system without costly upgrades.
Interconnection can affect:
- The maximum system size
- Whether electricity may be exported
- Required protection and control equipment
- Utility upgrade costs
- Engineering and construction requirements
- The target commercial operation date
- The project’s financing and return profile
Typical Stages of the Solar Interconnection Process
1. Early Feasibility Review
The project team reviews available utility maps, hosting-capacity information, nearby electrical infrastructure and applicable interconnection rules.
This early review can help identify obvious constraints, but it does not guarantee that capacity will be available when the formal application is submitted.
2. Preliminary System Design
The engineering team develops enough information to support the application. Depending on the utility, this may include:
- Proposed system size
- Site plan
- Single-line diagram
- Inverter and equipment specifications
- Point of interconnection
- Export or non-export operating approach
The design should be sufficiently developed to support review while preserving flexibility if the utility identifies a constraint.
3. Application Submission
The project team submits the required application forms, technical documents and fees. The utility reviews the package for completeness before beginning its technical evaluation.
Missing or inconsistent information can delay the application, so the development and engineering teams should review the package together before submission.
4. Initial Utility Review
The utility screens the project against applicable technical criteria. Some smaller or less complex projects may proceed through an expedited process, while others require additional study.
The utility may request clarifications, corrections or supplemental technical information during this stage.
5. Supplemental or Detailed Studies
If the project does not pass the initial review, the utility may perform additional studies to evaluate thermal loading, voltage, protection, power quality or other system impacts.
Study timelines and costs vary. Larger projects or constrained circuits may require several rounds of analysis.
6. Upgrade Determination and Agreement
The utility identifies any equipment, protection changes or grid upgrades required to connect the system. It may then issue an interconnection agreement or a study result that defines the project’s obligations.
The project team should evaluate the cost, scope, schedule and commercial implications before accepting the proposed requirements.
7. Design, Permitting and Construction
After the requirements are sufficiently defined, the project team incorporates them into the final design, obtains permits, procures equipment and constructs the system.
Utility-owned upgrades may follow a separate design, procurement and construction schedule that the project team does not directly control.
8. Testing, Inspection and Permission to Operate
After construction, the system may require electrical inspections, witness testing, utility-meter installation, settings verification and submission of final documentation.
The utility issues permission to operate, often called PTO, after confirming that the applicable requirements have been satisfied. The system should not operate in parallel with the grid before the required authorization is received.
Common Interconnection Risks
- Limited hosting capacity at the proposed location
- Unexpected grid-upgrade costs
- Long study or utility-construction timelines
- Changes to the proposed point of interconnection
- System-size limitations
- Export restrictions
- Long-lead protection, control or switchgear equipment
- Application deficiencies or inconsistent design documents
- Misalignment between utility, permitting and construction schedules
Questions to Ask During Development
- Which utility tariff and interconnection procedure apply?
- Is the proposed project exporting or non-exporting?
- What information is required for a complete application?
- Are preliminary capacity maps or screening tools available?
- What studies may be required?
- Who is responsible for utility upgrades and their cost?
- How long are utility studies, agreements and construction expected to take?
- What milestones must be completed before permission to operate?
- Which assumptions should be reflected in the project schedule and financial model?
How to Use the Interactive Roadmap
- Start at the beginning of the development process.
- Open each stage to review the major activities and decisions.
- Identify which party owns each task.
- Note the information required before moving to the next stage.
- Record schedule dependencies and unresolved risks.
- Revisit the roadmap as the utility provides new information.
The roadmap is most useful as a project-orientation and planning tool. Actual requirements and sequencing should always be confirmed with the applicable utility or grid operator.
Explore the Interconnection Process
Use The Energy Academy’s interactive roadmap to follow the major stages, responsibilities and decisions involved in connecting a commercial solar project to the grid.
Explore the Interactive Interconnection Roadmap
For additional background, explore The Energy Academy’s solar development learning resources.