A supply-side solar connection is rarely rejected for the reason the designer expects. The sizing is usually right. The comment comes from the tap point. Typical triggers are a connector without a line-side marking, a splice inside a utility-sealed compartment, or a disconnect that the utility wants fused and the plan set shows as a breaker.
This guide covers the mechanics of a supply-side connection and how each piece appears on a plan set. It is written for installer operations managers and permit coordinators in the US. It does not cover the busbar math for load-side connections. That sits in our NEC 705.12 guide, which also explains the 120% rule.
Quick answer. A supply-side connection ties the inverter output to the service conductors ahead of the main service disconnect, so the busbar 120% rule does not apply. NEC 705.11 governs it. That means conductors sized from 125% of inverter output current with a 6 AWG copper minimum, a listed line-side splice or tap, a service-rated disconnect with overcurrent protection, and bonding. Subsection letters differ by NEC edition, and utilities add limits.
Sourcing note. NFPA publishes the NEC behind a login, so we did not read the code text directly. Every rule below comes from IAEI Magazine, Mike Holt Enterprises, Mayfield Renewables, UL Solutions, SolarAPP+ and utility documents, each named next to the rule with its NEC edition. Check the adopted edition and local amendments before you issue drawings.
What is a supply-side connection for solar, and when does a design need one?
A supply-side connection, also called a line-side tap, connects the PV output to the service conductors between the utility meter and the main service disconnect. The solar source does not share a busbar with the main breaker. That is why the 120% busbar limit does not apply to it.
Designs reach this method when the busbar methods and a main breaker derate cannot deliver the system size, or when a panel upgrade is impractical. The NEC 705.12 guide lists the other routes, including a subpanel and a power control system, so test those first.
The price of this method is paperwork and physical work at the service entrance. The utility and the authority having jurisdiction (AHJ) both have a say. Our NEC 705 glossary entry gives the short definitions if you need them.
What does NEC 705.11 require, edition by edition?
The subsection letters moved between the 2020 and 2023 editions. A comment that cites “705.11(E)” means ground-fault protection in one edition and bonding in the other. Name the edition on the drawing and in the comment response.
| Topic | NEC 2020 | NEC 2023 | NEC 2026 (reported only) |
|---|---|---|---|
| Section title | 705.11 Supply-Side Source Connections, new in 2020 | Retitled Supply-Side Source Connections; (A) Service Connections rewritten with three subsections | Not read |
| Output limit | (A): sum of source output current ratings must not exceed the service conductor ampacity, unless a power control system under 705.13 limits it | (A) rewritten; wording not confirmed from a primary text | Not read |
| Conductors | (B): size per 705.28, not smaller than 6 AWG copper or 4 AWG aluminum; wiring method per 230.30 (underground) or 230.43 (aboveground) | (B) expanded; same 6 AWG copper and 4 AWG aluminum or copper-clad aluminum minimums reported | Not read |
| Overcurrent device location | (C): inside a building, within 10 ft of conductor length in dwelling units and 16.5 ft in other occupancies, or, in other occupancies, within 71 ft with cable limiters inside 16.5 ft; outside, in a readily accessible outdoor location or at the first readily accessible point on entry | Fixed distances no longer in the text; overcurrent protection moved to (F) and refers to Article 230, Part VII | Reported: length limits reinstated in 705.11(C)(1), measured as actual conductor length |
| Connections | (D): listed connectors per 110.14; modified equipment per manufacturer instructions or field evaluated with a field label; utility-controlled meter enclosures only with utility approval | (C): (1) splices or taps per 230.33 or 230.46, (2) existing equipment, (3) utility-controlled equipment | Not read |
| Disconnect | Service-equipment-listed disconnect per 230.82(6) | (D): disconnecting means per Article 230, Parts VI to VIII | Reported: fewer 705.11 subsections for protection, disconnect and bonding than 2023, with more reliance on general rules |
| Ground-fault protection | (E): 230.95 for source output rated 1,000 A or more on a solidly grounded wye system above 150 V to ground and not above 1,000 V phase to phase | Handled through the Article 230 reference in (F) | Not read |
| Bonding | No separate subsection | (E): metal enclosures, raceways and cables bonded per Article 250 | Not read |
Sources: NEC 2020 rows from Mike Holt’s 2020 PV textbook excerpt and John Wiles in IAEI Magazine, January 2023. NEC 2023 rows from John Wiles in IAEI Magazine, March 2023, Mike Holt in EC&M, September 2024 and Mayfield Renewables, February 2024. The 2023 minimum conductor sizes and the 230.33 or 230.46 wording come from a continuing-education page that reproduces the 2023 text, which we treat as secondary. The Holt EC&M article does not name its edition, so we matched its subsection layout to the IAEI description of the 2023 text.
What did 2026 change, and how firm is that?
Mayfield Renewables reported in January 2026 that the 2026 NEC reinstates the conductor length limits in 705.11(C)(1). It says the distances are actual conductor length, not straight-line distance. See the Mayfield 2026 summary. That article does not list the distances. A GreenLancer summary gives 10 ft and 16.5 ft with a cable limiter option, but it does not quote NFPA text.
We treat all of this as reported. Our 2026 NEC changes guide takes the same position. Design to the edition your jurisdiction has adopted, which our state adoption guide helps you find. Our NEC 2023 vs 2020 comparison covers the other Article 705 and 690 differences.
Where can the tap physically land?
The tap point decides how much utility and AHJ friction the project meets. The table lists the common landing spots, the code hook for each and where utilities push back. Use the tap-point column on the plan set, not the code column.
| Tap point | How it is made | Code hook | Common restriction |
|---|---|---|---|
| Meter socket adapter | An adapter between the meter and the socket takes the PV wires | 2020 705.11(D) and 2023 705.11(C)(3): utility-controlled meter enclosures only with utility approval | PG&E allows only its own Green Meter Adapter in that program; the utility installs it |
| Line-side lugs or a listed tap in the customer section of the service equipment | Connector on the service entrance conductors or a lug kit in the equipment | 230.46 listed splice or tap; 2020 705.11(D) or 2023 705.11(C)(2) for equipment modification | Equipment manufacturer instructions or a field evaluation label |
| Tap box or gutter added between meter and main | Service conductors run through a new enclosure and the PV conductors tie in there | 230.46 for the splice; enclosure fill and wiring method rules | APS accepts a field-installed NEMA 3R gutter or tap box on meter-main or main-lug-only equipment |
| Additional set of service entrance conductors or a new service | PV output lands on its own service conductor set | 705.11(A) service connection methods | APS treats a supply side connection as a new service under the NEC |
| Inside the utility sealed meter, CT or pull section | Tap made in the utility compartment | None that overrides the utility | SCE, APS and Xcel Colorado do not allow it |
Utility statements come from PG&E bulletin TD-7001B-007, the SCE NEM Interconnection Handbook, the APS supply side connection excerpt and the Xcel Energy Colorado PV line diagram form.
What does 230.46 mean for the connector you specify?
NEC 230.46 covers splices and taps on service conductors. UL Solutions wrote in IAEI Magazine in January 2023 that, effective 1 January 2023, wire connectors used on the line side must be listed for that use. UL marks connectors it has investigated with “SR” or the words “suitable for use on the line side of the service equipment,” under product category ZMVV. See the UL Question Corner column.
Put the connector manufacturer and model on the plan set, and carry the marking into the equipment schedule. A generic note that says “listed tap connector” invites a comment. A named product with its line-side marking does not.
What about meter-main combinations and modified equipment?
Existing equipment is listed as built. UL’s 2016 line side tap guide notes that some utilities and inspectors treat a line side tap as a modification of certified equipment. See UL’s Line Side Taps installation guidelines. UL describes a field evaluation that ends in a serialized label on the panel enclosure.
John Wiles wrote for the 2020 edition that the connection between the meter and main breaker in a listed meter-main combination cannot be made in the field. His options were a UL 508 shop recertification, a field inspection by a nationally recognized testing laboratory, or replacing the unit with a separate meter socket and load center. That is one author’s reading, not an AHJ ruling, so confirm it locally.
APS adds that drilling, tapping or replacing factory bus is not allowed unless the manufacturer or its representative does it. If the manufacturer offers no kit, APS asks for a field evaluation letter from a nationally recognized testing laboratory and a photo of the label.
How are the supply-side conductors and fuses sized?
Size in this order: inverter output current, conductor, overcurrent device, disconnect rating. Then check the result against the utility limits. John Wiles describes the 2020 705.28 method as the largest of three values. These are 125% of the inverter maximum circuit current, that current after conditions-of-use factors, and the 240.21(B) result where the circuit feeds a smaller feeder. Overcurrent devices on non-generator sources must be rated at least 125% of the maximum currents (705.30).
Illustrative example, not a project design. Assume one 15 kW AC inverter at 240 V single phase, a 200 A service, copper conductors and a 75 C terminal rating. Ampacities are read from NEC Table 310.16, which we did not open for this guide, so verify them against the adopted edition.
| Step | Calculation | Result |
|---|---|---|
| 1. Inverter output current | 15,000 W / 240 V | 62.5 A |
| 2. Minimum conductor ampacity | 62.5 A x 125% | 78.1 A |
| 3. Conductor | 6 AWG copper at 75 C is 65 A, too small; 4 AWG copper at 75 C is 85 A | 4 AWG copper |
| 4. Minimum overcurrent device | 62.5 A x 125%, next standard size | 80 A fuses |
| 5. Disconnect | At least 60 A, so a 100 A fused service-rated switch with 80 A fuses | 100 A switch |
| 6. Output limit check (2020 705.11(A)) | 62.5 A against the service conductor ampacity | Passes on a 200 A service |
Now apply the utility layer. APS asks for a conductor not smaller than 2 AWG copper or the disconnect rating, whichever is larger, so the 4 AWG result is upsized on an APS job. PG&E’s Green Meter Adapter path caps combined source current at 60 A, so 62.5 A is out of that program. The same bulletin caps the system at 14.0 kW, which also excludes this inverter.
The 10 ft figure deserves care. Mayfield reports that NEC 2023 has no fixed maximum length. SCE and APS still ask for the overcurrent device or disconnect within 10 ft of the connection, and the APS excerpt cites NEC 705.31 and predates the 2020 edition. Design to the stricter of the code edition and the utility.
What disconnect does a supply-side connection need?
The disconnect is a service-type device, not a convenience switch. In the 2020 edition, 230.82(6) requires a disconnect listed as suitable for service equipment, with overcurrent protection per Part VII of Article 230 (Wiles, IAEI, 2023). The 2023 edition points to Article 230, Parts VI to VIII, for the disconnecting means (Holt, EC&M, 2024). Where fuses protect the circuit, the disconnect sits on the service side of the fuses.
Utilities then set the type and place.
- PG&E: a fused AC disconnect 2 ft to 10 ft from the meter panel, built to PG&E’s disconnect requirements for generation customers.
- SCE: a single fusible, visible-open, lockable AC disconnect directly adjacent to the point of connection.
- APS: a fused service disconnect rated at least 60 A, plus a second utility disconnect switch, mounted within 10 ft on the same wall as the service entrance section.
- Xcel Colorado: a lockable disconnect with visible open, labeled “PV AC Disconnect,” when a line side tap is used.
Wiles also flagged the 2020 emergency disconnect rule in 230.85 for one- and two-family dwellings. It left unclear where the PV tie-in sits relative to that device. Ask the AHJ before you draw the order of devices.
How are grounding and bonding handled?
NEC 2023 added a bonding subsection, 705.11(E). Metal enclosures, raceways and cable systems that hold supply-side conductors are bonded per Article 250 (Holt, EC&M, 2024). The 2020 edition had no matching subsection, so designers worked from Article 250 directly.
Ryan Mayfield’s 2022 article on the 2020 edition gives the working method. Run a neutral from the service conductors to the PV disconnect even if the inverter does not need one. Establish the neutral-to-ground bond at the service disconnecting enclosure per 250.24. He notes that grounding electrode conductor routing is still debated. See Mayfield’s 2020 705.11 Code Corner. That is a consultancy view, so confirm GEC routing with the AHJ.
Utilities are more specific. APS asks for the neutral-to-ground bond to be re-established in an externally mounted supply side disconnect, with the GEC landed on the neutral bus. If the tap is made through a breaker or fused switch inside the service entrance section, the existing bond is enough. PG&E’s adapter path requires an equipment grounding conductor from the disconnect to the service grounding system.
Which utility rules restrict a supply-side tap?
Utility rules decide whether the method is available at all. The table compares four documents we read in full. Each is dated, and each may have been revised since, so open the current version before you design.
| Utility and document | Where the tap can go | Disconnect and protection | Paperwork and process |
|---|---|---|---|
| PG&E, Green Meter Adapter bulletin TD-7001B-007, Rev 2, 15 Feb 2021 | PG&E-installed adapter between meter and socket; underground single-phase 120/240 V panel up to 125 A with the main breaker and meter socket in one panel | PG&E-approved fused disconnect 2 ft to 10 ft from the panel; 6 AWG copper in liquidtight nonmetallic conduit; combined source limit 14.0 kW and 60 A | AHJ must permit the line-side connection; some AHJs do not approve it; PG&E installs the adapter before the final building permit issues |
| SCE, NEM Interconnection Handbook v8, June 2020, section 5.3 | Never in SCE metering, CT or pull sections; SCE encourages load-side instead | Fusible, visible-open, lockable AC disconnect adjacent to the tap; overcurrent device within 10 ft of the connection | SLD with signed PE stamp, line of delineation, “Line Side Tap” callout, plot plan, photos, signed final inspection and a Line Side Tap Letter; SCE reviews location and method case by case |
| APS, Supply Side Connection excerpt, Rev 09/27/19 | Customer section of the service entrance section or a field-installed NEMA 3R gutter or tap box; never in the sealed metering compartment or pull section | Externally mounted fused disconnect within 10 ft, rigid metal conduit between tap and disconnect, two-disconnect configuration | Only APS can de-energize the service; AHJ green tag before re-energizing; stamped third-party inspection where the AHJ does no plan review |
| Xcel Energy Colorado, small third-party PV line diagram form, drawing revised 9/25/14 | No piercing tap connectors inside a self-contained meter socket or CT enclosure | AC disconnect with visible open if a line side tap is used; optional production meter within 10 ft of the utility meter | One-line must carry the form notes or it is denied; the form is old, so confirm the current Xcel standard |
Two further points matter at the permit desk. First, PG&E’s September 2026 Greenbook update bulletin, effective 3 November 2026, says only meter socket adapters explicitly approved by PG&E may be installed behind its meter. See bulletin TD-7001M-B013. Second, our PG&E Rule 21 guide, APS guide and Xcel guide cover the wider application process for those utilities.
Does SolarAPP+ allow a supply-side connection?
The SolarAPP+ platform supports it. Its release notes show supply-side inputs added in 2021 and main-lug-only support added in December 2021. Support then narrowed. A January 2022 note limited main-lug-only panels to NEC 2017, and a December 2022 note said NEC 230.71 means those panels are not supported. See the SolarAPP+ release notes. Its eligibility article caps projects at a 400 A service, 225 A disconnects and busbars, and 38.4 kW.
A jurisdiction can still exclude the method. Our LADBS SolarAPP+ guide lists supply-side interconnection as a disqualifier for Los Angeles. Check each AHJ’s own SolarAPP+ scope.
How does a supply-side connection appear on the single-line diagram?
The single-line diagram (SLD) should let a reviewer find the tap point, the protection and the bond without reading the notes. Our single-line diagram guide covers general layout. The table below lists what a supply-side SLD adds. Our SLD glossary entry has the term.
| SLD element | What to show | Why |
|---|---|---|
| Method callout | ”Supply-side connection per NEC [edition] 705.11” and, where the utility uses the term, “Line Side Tap” | Names the edition and matches utility vocabulary; SCE asks for the callout |
| Line of delineation | A boundary between the utility section and the customer section of the service equipment | SCE asks for it; it proves nothing is tapped in a sealed section |
| Tap point | Location in the service equipment or tap box, connector manufacturer and model, line-side marking | Supports 230.46 |
| Tap conductors | Size, material, insulation and temperature rating, wiring method, length to the overcurrent device | Supports 705.28 and the length rule or utility limit |
| Disconnect and fuses | Rating, fuse size and class, service-rated listing, lockable and visible-open where required, location | Supports 230.82(6) in 2020 or Article 230 in 2023 and the utility rule |
| Neutral and bonding | Neutral run, where the neutral-to-ground bond is made, GEC connection | Supports the bonding subsection and the utility bond rule |
| Service data | Service rating, main breaker, service conductor size, meter and any production meter | Supports the output limit check |
| Equipment modification | Manufacturer kit reference or the field evaluation label | Supports 2020 705.11(D) or 2023 705.11(C)(2) |
| Utility notes | The utility form notes, if the utility requires them on the drawing | Xcel Colorado denies one-lines without them |
SCE asks for a signed PE stamp on the SLD for a line side tap. Whether any project needs a stamp, and who provides it, is a state and utility question. For our work, stamping requirements are confirmed at quote stage.
If you want drawings that carry these callouts, our US solar permit design service prepares permit plan sets from your site data. Our commercial electrical design checklist covers the larger-system view.
What do inspectors and utility reviewers check on a supply-side tap?
Use this list before submission. Each item traces to a source above.
- Edition and amendments. The drawing names the NEC edition the AHJ has adopted and any local amendment.
- Connector marking. The listed splice or tap is named and carries the line-side marking (230.46).
- Modification authority. A manufacturer kit or instruction, or a field evaluation label, covers any change to the service equipment.
- Torque. The plan set carries the connector torque value, which UL’s field evaluation checks with a calibrated tool.
- Sealed compartments. Nothing is tapped or routed through a utility metering, CT or pull section, and no seal is broken by the installer.
- Conductors. Size, wiring method and length match the sizing calculation and the utility limit.
- Disconnect. The device is service-rated, matches the fuse size on the SLD, and meets the utility rule on lockable and visible-open.
- Bond. The neutral-to-ground bond and GEC connection match the SLD.
- Labels. Utility placards and interconnection signage are on site. SCE specifies a “SOLAR INTERCONNECTION TERMINATION SECTION” placard in its special exception for building a customer section for the tap.
- Outage and energization. The utility has scheduled the outage, and final inspection is signed before permission to operate. Our interconnection rejection guide shows how missing items stall the application.
When does supply-side beat load-side?
Supply-side wins when the busbar is the constraint and the service equipment can take a tap. It loses when the utility or AHJ discourages it or the equipment cannot be modified. The table compares the two on situations, not on cost, because we have no cost data to publish.
| Situation | Supply-side tends to win | Load-side tends to win | Check first |
|---|---|---|---|
| PV output exceeds the busbar headroom | Yes, if the other busbar routes fail | If a derate, subpanel or power control system fits | The 705.12 options |
| Panel upgrade is impractical, such as a rental or old equipment | Yes, if the equipment can be modified | Manufacturer kit or field evaluation | |
| System is small and inside the headroom | Yes, fewer utility steps | 120% result | |
| Utility discourages line-side taps (SCE) | Yes, where headroom exists | Current utility handbook | |
| PG&E residential, 125 A panel or less, up to 14.0 kW and 60 A | Adapter path is available | Panel type, AHJ pre-approval | |
| Meter-main combination with no customer section | Hard without a tap box or replacement | Yes, if headroom exists | Equipment listing and utility rule |
| Larger system with new switchgear and a customer section | Yes, practical | Utility interconnection process | |
| AHJ uses SolarAPP+ and excludes the method | Yes, or a manual permit | AHJ SolarAPP+ scope |
How can Heaven Designs help with a supply-side plan set?
Heaven Designs is a design and engineering firm. It does not install or sell hardware. For US installers, the permit design service covers the plan set, SLD and calculations. The supply-side items above, tap point, connector, disconnect, bond and utility notes, become named elements of the drawing. Turnaround is agreed at scoping.
- Solar permit design for US projects for plan sets and SLDs.
- Design samples if you want to see a deliverable first.
To discuss a project, use our contact page. We reply within 1 business day.
FAQ
Is a supply-side connection the same as a line-side tap?
In everyday use, yes. NEC 705.11 uses the term supply-side source connection. Utilities and the UL guidance use line-side tap. Use the code term on the SLD and add the utility term if the utility uses it.
Does a supply-side connection need a separate disconnect?
Yes. The disconnect must meet the service-equipment rules in Article 230 for the edition in force. Utilities then add type and location rules, such as fused, lockable and visible-open.
Can I tap inside the utility meter socket?
Only where the utility approves. The 2020 and 2023 editions both limit meter enclosures under exclusive utility control to utility-approved connections. SCE, APS and Xcel Colorado state that customer taps are not allowed in sealed sections.
How long can the tap conductors be?
It depends on the edition. NEC 2020 set 10 ft in dwelling units and 16.5 ft elsewhere for connections inside a building. NEC 2023 removed fixed distances. NEC 2026 is reported to restore them. Utilities such as SCE and APS ask for 10 ft regardless.
Does the 120% rule apply to a supply-side connection?
No. The busbar rule governs load-side connections. A supply-side connection is limited by the service conductor ampacity in the 2020 edition and by the sizing and protection rules in 705.11.
Will the utility or AHJ accept my supply-side design?
We cannot say. Acceptance depends on the utility document in force, the AHJ’s adopted edition and the equipment. Confirm project-specific requirements with the utility and the AHJ before you design.