PG&E Rule 21 solar interconnection starts with a jurisdiction decision, not an application form. The project team must confirm that Rule 21 governs the transaction. It must then describe one consistent facility across the application, drawings, equipment evidence, operating modes, and closeout record.
Direct answer. Use PG&E Electric Rule 21 for a project only when its jurisdiction and transaction fit the tariff. Record the requested export behavior, select the applicable review path, and reconcile every technical value before filing. Fast Track can include Initial Review and Supplemental Review. Projects that are ineligible or do not pass can require Detailed Study. A complete application, certified equipment, or export limit does not guarantee approval or avoid upgrades.
This guide is for solar and solar-plus-storage teams working in Pacific Gas and Electric Company territory. It explains project controls, not project-specific tariff interpretation. A qualified interconnection professional must verify the current tariff, program, portal instructions, and utility notices before the team acts.
The Rule 21 glossary entry owns the short definition. This article covers PG&E routing, evidence, review tracks, and submission quality.
When does PG&E Rule 21 apply?
The California Public Utilities Commission Rule 21 page describes Rule 21 as a tariff for generation connected under CPUC jurisdiction. It covers interconnection, operation, and metering requirements for covered investor-owned utility systems.
PG&E administers its own version in its service territory. That fact does not make Rule 21 the route for every PG&E-area project.
Start with a jurisdiction record:
| Question | Project record to preserve |
|---|---|
| Who is the serving utility? | Account record, meter identifier, and service address |
| What transaction is proposed? | Retail tariff, wholesale sale, self-supply, or another stated arrangement |
| Where is the point of interconnection? | Site map, coordinates, utility equipment, and electrical diagram |
| Is the connection on distribution or transmission facilities? | Utility confirmation and current service data |
| Will power cross the point of common coupling? | Maximum physical export and requested operating limit |
| Which tariff controls? | Title, section, sheet, advice filing, and effective date |
| Which program applies? | NBT, non-export, qualifying facility, or another verified program |
| Which version governs the request? | Filing date, transition rule, and written utility direction |
The current PG&E Electric Rule 21 tariff covers specified generating facilities on systems under CPUC jurisdiction. Its applicability section also names exceptions and other paths.
Do not reduce this decision to site location. A PG&E account can still involve a transaction that belongs under another interconnection framework.
Rule 21 versus the Wholesale Distribution Tariff
The CPUC states that FERC-jurisdictional distribution interconnections use the applicable Wholesale Distribution Access Tariff. PG&E calls its version the Wholesale Distribution Tariff, or WDT.
That boundary usually depends on the transaction and jurisdiction, not the color of the utility meter. A wholesale project does not become a retail Rule 21 project because it connects at distribution voltage.
Rule 21 versus CAISO procedures
PG&E Rule 21 directs generating facilities seeking certain transmission-system interconnections to the California Independent System Operator. The tariff also states specific exceptions. These include defined NEM and NBT facilities at or below a stated size, plus qualifying non-export facilities.
Do not apply the exception from memory. Verify the facility type, capacity definition, export method, point of interconnection, and current applicability sheet.
Rule 21 versus the permit process
Rule 21 does not replace a building, electrical, structural, or fire review. The utility evaluates grid connection under its tariff. The authority having jurisdiction evaluates construction under adopted requirements.
The same single-line diagram may support both packages. Approval in one process does not grant approval in the other.
Which document version controls the project?
The PG&E tariff PDF is a collection of sheets. Individual sheets can carry different advice numbers and effective dates. Do not assign one blanket effective date to the entire file.
For example, the applicability sheet in the source reviewed for this article identifies Advice 7540-E and an April 17, 2025 effective date. Many leading process sheets identify Advice 7692-E and an August 29, 2025 effective date. A later filing can change selected sheets without replacing every page.
Create a source register before making a design decision:
| Field | Example of a useful entry |
|---|---|
| Source title | PG&E Electric Rule 21 |
| Direct URL | Utility tariff PDF URL |
| Section and sheet | B.1, Sheet 15 |
| Advice number | Number printed on that sheet |
| Effective date | Date printed on that sheet |
| Access date | Date the team retrieved it |
| Project use | Jurisdiction, fee, screen, evidence, or deadline |
| Reviewer | Person who confirmed applicability |
Save the downloaded tariff with the application package. A bookmark proves where a file lived, but not which text supported a past decision.
When a portal instruction and tariff appear inconsistent, ask PG&E for written direction. Preserve the response with the rule register.
What are the PG&E Rule 21 solar interconnection review paths?
The current tariff separates Fast Track from Detailed Study. Fast Track includes Initial Review and, when needed, Supplemental Review. Detailed Study contains several possible study processes.
The path is a utility determination under the tariff. Project teams should not market Fast Track as automatic approval.
| Review stage | What it answers | Project-team action |
|---|---|---|
| Validation | Is the request complete and valid? | Cure missing or inconsistent information |
| Initial Review | Does the project pass Screens A through M? | Confirm inputs and review each reported result |
| Supplemental Review | Does it pass Screens N through P? | Authorize the review, pay an applicable fee, and validate the study case |
| Detailed Study selection | Which study process applies? | Evaluate Screens Q and R, notices, deposits, and commercial effects |
| Detailed Study | What impacts, facilities, or upgrades are identified? | Review assumptions, cost responsibility, design changes, and agreements |
Fast Track and Initial Review
PG&E Rule 21 says a complete and valid request normally receives Fast Track evaluation. An applicant can choose Detailed Study, and an ineligible project follows Detailed Study. Initial Review applies Screens A through M.
A pass can allow the project to proceed without Supplemental Review. A failed screen does not necessarily mean the facility cannot interconnect. The tariff states that further review or study may be required.
That distinction matters in project reporting. Use a status such as Initial Review screen not passed. Avoid a broad label such as utility rejected.
Supplemental Review
Supplemental Review applies Screens N through P under the current tariff. PG&E can require the applicant to authorize the step and pay the applicable non-refundable fee.
The tariff states a 20-business-day review period after the required authorization and fee are received. A fault-current study can extend that review by up to ten business days. Treat these as tariff conditions, not a delivery promise.
Confirm the current fee in Table E-1. Record the payment date, authorization date, accepted study case, and any written schedule modification.
Detailed Study
Projects can enter Detailed Study by choice, ineligibility, or a Fast Track result. PG&E Rule 21 names three processes:
- Independent Study Process.
- Distribution Group Study Process.
- WDT Transmission Cluster Study Process.
Screens Q and R help determine the applicable route. Electrical interdependence with other queued projects can affect the track.
Study entry is a commercial decision as well as a technical step. Deposits, upgrades, schedule exposure, design alternatives, and contract commitments may change. A qualified interconnection lead should review the notice before the team accepts or withdraws.
The interconnection application rejection guide explains how to classify utility notices without treating every return as a denial.
Should the project request a pre-application report?
The standard pre-application report is optional under the tariff reviewed here. It can provide early circuit information when PG&E has the requested data.
Section E.1 states a $300 non-refundable processing fee and a ten-business-day response after a completed request. Both values are volatile. Verify the current sheet before budgeting or promising a date.
The request must identify a proposed point of interconnection. PG&E allows location evidence such as coordinates, a site map, address, utility equipment number, meter number, account number, or a sufficient combination.
The standard report can include:
- Substation, area, or circuit capacity information.
- Allocated, queued, and available capacity information.
- Nominal circuit voltage and wiring configuration.
- Approximate circuit distance to the substation.
- Peak and minimum load data when available.
- Protective and voltage-regulating device counts.
- Whether three-phase power is available.
- Limiting conductor information.
- Known constraints at the proposed location.
PG&E also offers enhanced packages with separate fees and data fields. The tariff says enhanced requests are submitted in parallel with the standard request. It also states conditions for an additional fee when the standard report is excluded.
Do not request a report before the point of interconnection is stable. Data for the wrong pole, meter, or service location can create false confidence.
Use the report to frame risk, not to reserve capacity. Rule 21 warns that pre-application data can change and can be unavailable. The report does not replace an interconnection request or study.
What belongs in a complete PG&E submission record?
A good package lets the utility identify the customer, location, generating facility, operating case, equipment, and requested connection. Exact forms depend on the program and current instructions.
Build the record in six groups.
1. Customer and authorization records
Confirm the legal customer name, account, meter, service address, applicant, system owner, and authorized agent. If a third party submits the request, preserve the signed authorization required for that role.
Names should match across utility records, contracts, application fields, and signatures. A correct drawing cannot cure an invalid authorization.
2. Site and point-of-interconnection records
Preserve a site plan, coordinates, service-equipment photographs, utility equipment identifiers, and the proposed connection point. Mark the point of common coupling and ownership boundary when the tariff or utility requires them.
For commercial work, the three-phase interconnection checklist covers service, transformer, protection, metering, and instrument-transformer inputs.
3. Facility ratings and operating modes
Record generator DC rating, inverter AC kW, aggregate kVA, storage charge and discharge ratings, power factor capability, and maximum physical export. Then state the requested export behavior.
Storage creates more than one possible mode. The package should explain charging source, simultaneous solar and battery operation, backup behavior, islanding controls, and export during each allowed state.
4. Electrical drawings
The drawing set should use the same equipment identifiers and ratings as the application. Depending on project scope, useful records include:
- Site plan with the proposed point of interconnection.
- Single-line or three-line diagram.
- Existing service and utility transformer data.
- Service, switchboard, panel, conductor, and disconnect ratings.
- Protection, metering, and control locations.
- Current-transformer and potential-transformer data.
- Grounding and transformer winding information.
- Export-control measurement and command paths.
- Equipment schedules tied to exact model numbers.
The solar permit package checklist covers permit documents. Keep the permit and interconnection scopes distinct, then reconcile shared facts.
5. Equipment and certification evidence
Preserve data sheets, model identifiers, certification records, firmware or software versions when applicable, and the source used to validate the equipment.
The California Energy Commission Solar Equipment Lists include inverters, energy storage systems, batteries, meters, and power control systems. The CEC explains that some utilities and local governments use these lists.
The CEC also warns that manufacturer-submitted information is not independently confirmed. A listing is useful evidence, but it is not a warranty or project approval.
6. Closeout and commissioning records
Plan closeout before construction. The file may need final inspection evidence, signed agreements, approved settings, commissioning results, as-built drawings, and equipment-change records.
Do not let the construction folder become the only source of truth. Interconnection closeout must point back to the accepted application and approved design.
How do IEEE 1547-2018 and UL 1741 fit?
PG&E Rule 21 says it has been harmonized with IEEE 1547-2018. It also says Rule 21 controls if a conflict exists between the tariff and referenced standards.
For applicable generation technology below 50 kV at the point of interconnection, the current tariff requires IEEE 1547-2018 and related certification requirements. At 50 kV or above, PG&E directs teams to its Interconnection Handbook and applicable NERC and CAISO requirements.
The IEEE public overview of IEEE 1547-2018 describes performance, operation, testing, safety, maintenance, abnormal-condition response, power quality, islanding, and interoperability topics.
UL 1741 covers inverters, converters, controllers, and interconnection system equipment for distributed energy resources. The UL 1741 public scope states that interactive equipment requirements supplement IEEE 1547 and IEEE 1547.1.
These layers serve different purposes:
| Evidence layer | Main question |
|---|---|
| IEEE 1547-2018 | What interconnection and interoperability behavior does the standard address? |
| IEEE 1547.1 | How is conformance with applicable functions tested? |
| UL 1741 and applicable supplements | What product evaluation evidence applies to the equipment? |
| CEC equipment record | Does the exact model appear with the relevant reported attributes? |
| PG&E Rule 21 | What tariff requirements and settings apply to this project? |
| Utility acceptance record | What did PG&E accept for the stated facility and revision? |
Do not verify an inverter by brand or family name. Match the exact model, suffix, rating, firmware where required, certificate scope, and CEC record.
The IEEE 1547-2018 guide explains the standard layer. The UL 1741 SB verification guide covers model-level evidence.
How should export, non-export, and limited export be documented?
Export is an operating case at the point of common coupling. It is not a marketing label.
For each allowed mode, record:
- Which sources can operate.
- Which loads are assumed.
- The maximum physical power flow toward the grid.
- The requested export limit.
- The measurement point and sensors.
- The controller and command path.
- The response if communications or controls fail.
- The commissioning test and pass evidence.
PG&E Rule 21 includes several non-export and limited-export methods. They have defined conditions. Some use certified power control systems, inadvertent-export limits, or limited-generation profiles.
Do not claim that choosing non-export automatically avoids Initial Review, Supplemental Review, Detailed Study, protection requirements, or distribution upgrades. The utility evaluates the submitted method under the tariff.
The application, diagram, controls narrative, equipment evidence, study case, and commissioning plan must use the same export definition. A zero-export portal selection is not enough if the drawing shows no measurement point or control behavior.
For storage, identify grid charging and charging from onsite generation. State whether solar and storage can discharge together. Explain backup operation and the transition between grid-connected and isolated modes.
The solar and storage plan-set guide covers the drawing implications. The NBT glossary entry gives program context without replacing the tariff.
Use the four-record Rule 21 reconciliation matrix
Most preventable submission problems are cross-file problems. A value can be valid in isolation and still conflict with another record.
The four-record Rule 21 reconciliation checks the application, drawings, supporting evidence, and final released package as one system. It gives each shared value an accountable owner and a closing test.
Use this matrix before filing and after every material change:
| Controlled field | Application or portal | Drawing or schedule | Supporting evidence | Final check |
|---|---|---|---|---|
| Customer name | Exact account identity | Title block when used | Authorization | Same legal entity |
| Service address | Account and site fields | Site plan | Utility record | Same service location |
| Point of interconnection | Location field and coordinates | Site plan and electrical diagram | PG&E response or site evidence | Same physical point |
| Inverter model | Exact model and quantity | Equipment schedule and SLD | Data sheet, certificate, CEC record | Exact suffix and rating |
| Solar AC rating | Aggregate kW and kVA | SLD calculation and schedule | Manufacturer ratings | Same aggregation method |
| Storage rating | Charge, discharge, kW, kVA, and energy | SLD and storage schedule | Product record | Every operating mode covered |
| Export case | Requested limit and program | Controls narrative and SLD | PCS record and test plan | Same value at the same point |
| Transformer | Rating, impedance, winding, and ownership | SLD or three-line diagram | Nameplate and utility data | No guessed value |
| Protection | Requested functions and settings | Relay table and trip path | Device record and settings file | Same device tags |
| Metering | Meter type and purpose | Physical location and wiring | Utility requirement | Revenue and control metering separated |
| Program | Tariff and rate option | Notes only when needed | Current rule register | No outdated label |
| Revision | Application revision | Drawing revision | Transmittal and change log | One released package |
Give every row an owner. The owner does not invent missing information. The owner closes the field using an approved source.
Run the matrix three times:
- Before the application is submitted.
- After PG&E issues a technical or completeness notice.
- Before equipment procurement or a field substitution is released.
For a returned package, use the solar redline resubmission guide for drawing control. Utility notices still need their own response register.
What happens after an equipment or design change?
A submitted interconnection request describes a defined facility. Equipment swaps, rating changes, added storage, revised controls, and a moved connection point can change that facility.
PG&E Rule 21 defines material modification within the tariff. The utility decides how the definition applies to a proposed change.
Open a change review for any of these events:
- Inverter model, quantity, firmware, or rating changes.
- Battery model, power, energy, or operating mode changes.
- The AC or kVA total changes.
- The point of interconnection moves.
- The export method or limit changes.
- A transformer, relay, switchboard, or service changes.
- The project adds a generator or other distributed resource.
- The customer, system owner, or authorized agent changes.
The change record should identify every affected application field, drawing, certificate, study input, permit document, procurement record, and commissioning step.
Ask PG&E whether the proposed change can be accepted under the active request. Retain the written direction. Do not conceal a substitution inside an as-built package.
How should teams read Rule 21 fees and timelines?
Fees and response windows belong to defined steps. They are not project-wide price or schedule promises.
Read any number with five qualifiers:
- Which tariff section states it?
- Which project class receives it?
- What event starts the clock?
- What missing item or study can change it?
- Can the parties modify the timeline in writing?
Rule 21 says PG&E uses reasonable efforts to meet its stated timelines. It also allows written modifications under the tariff. A project schedule should retain contingency for deficiencies, studies, applicant decisions, construction, and external approvals.
The often-cited 30-business-day permission-to-operate provision is narrow. The current tariff applies it to qualifying NEM-1, NEM-2, or NBT-1 facilities at 1 MW or smaller. The clock follows receipt of a complete request, supporting records, required payments, signed agreement, and final inspection evidence.
The same section discusses projects with non-certified equipment, new service, interconnection facilities, or distribution upgrades. It advises earlier submission and states that added review time may be needed.
Do not turn that provision into PG&E approves solar in 30 days. It is neither a universal review clock nor a guarantee.
Maintain a live deadline register for utility notices, payments, elections, agreements, and closeout. Record the start event and proof of completion for each item.
What causes avoidable PG&E Rule 21 delays?
The tariff can require study even when a package is accurate. Still, teams can prevent many self-created delays.
Watch for these defects:
- The wrong tariff or transaction path.
- A customer name that does not match the utility account.
- An unstable or poorly identified point of interconnection.
- Different inverter models across the portal, SLD, and certificate.
- AC kW and kVA totals calculated with different equipment revisions.
- Storage modes omitted from the controls narrative.
- Export settings with no measurement, failure response, or test method.
- A CEC listing used as proof of project acceptance.
- Missing transformer, fault-current, metering, or protection data.
- Permit revisions that never reach the interconnection package.
- A late utility response, fee, agreement, or study election.
- Construction that differs from the accepted equipment and drawings.
Use the solar site survey versus satellite design guide when the existing service record is incomplete. Field evidence and utility data should resolve unknowns before the package freezes.
How can Heaven Designs support the drawing package?
Heaven Designs can prepare coordinated solar and storage drawings within an agreed project scope. That work can include site plans, single-line diagrams, equipment schedules, controls details, and revisions tied to documented utility comments.
Our US solar permit design service can help align shared data across permit and interconnection drawing sets. You can review sample design deliverables before defining the required output.
The applicant, customer, PG&E, and qualified interconnection professionals keep their own responsibilities. Heaven Designs does not control tariff decisions, utility study results, queue position, fees, upgrades, or permission to operate.
If you need drawing support, send the current project record. Include the utility account context, applicable tariff or program, portal export, site information, equipment records, submitted drawings, and every PG&E notice.
Frequently asked questions
Is PG&E Rule 21 the same as NEM 3.0 or NBT?
No. Rule 21 governs covered interconnection, operation, and metering requirements. NBT is a compensation tariff commonly associated with California’s successor to earlier net-metering structures. A project can need both interconnection and rate-program records.
Does passing Fast Track mean PG&E has issued permission to operate?
No. A Fast Track result addresses the interconnection review path. Agreements, construction, inspection, commissioning, metering, and closeout requirements may remain. Follow the project notice and tariff.
Does a failed screen mean PG&E denied the project?
No. The current tariff says a failed Fast Track evaluation means further review or study is needed. The project may enter Supplemental Review, Detailed Study, an agreed modification process, or another stated path.
Can a non-export solar or battery project skip study?
Do not assume that. Rule 21 provides defined non-export methods and special provisions. PG&E still evaluates the project, equipment, controls, protection, and system effects under the applicable process.
Is equipment on the CEC list automatically accepted?
No. The list is an evidence source. The exact model and reported functions must match the project. PG&E still determines tariff compliance and project acceptance.
What is the difference between Initial Review and Supplemental Review?
Initial Review applies Screens A through M. Supplemental Review applies Screens N through P when required. The tariff defines the screens, authorization, fee, timing conditions, and possible next steps.
Should a team order a pre-application report for every project?
No. It is optional. It can help when early circuit data will change a site, size, or operating decision. It does not reserve capacity or replace a formal review.
Who should approve a Rule 21 submission?
A qualified interconnection professional should confirm jurisdiction, tariff version, technical case, and response path. Other licensed or regulatory review may be needed for the project scope.
Final review and freshness note
This guide was researched against public sources accessed on September 26, 2026. Rule 21 remains subject to tariff filings, CPUC proceedings, utility instructions, and equipment-list changes.
A qualified interconnection professional must verify every project-specific fee, deadline, screen result, study decision, equipment record, and utility notice before submission or publication use.