National Grid interconnection requirements
Sample preview — compiled from public sources 2026-08-19
Who this applies to
National Grid runs electric distribution in two states with two entirely different interconnection regimes, and this page keeps them separate throughout:
- Upstate New York (Niagara Mohawk territory) — distributed generation and energy storage with an AC nameplate rating of 5 MW or less interconnect under the New York State Standardized Interconnection Requirements (SIR), the Public Service Commission framework shared by the state's investor-owned utilities. The SIR document current at review is effective February 9, 2026.
- Massachusetts (Massachusetts Electric / Nantucket Electric) — DG interconnects under the DPU-approved Standards for Interconnection of Distributed Generation, filed as National Grid's tariff M.D.P.U. No. 1599 (effective June 1, 2025 confirm current revision).
Covered project types in both states: solar, storage, and solar-plus-storage operating in parallel with the distribution system — residential through commercial and community-scale. Out of scope for this page: systems above 5 MW in New York (utility-specific large-generator process), wholesale and transmission-level interconnections, National Grid's other service areas, and gas-side work.
Application pathway overview
New York — SIR pathways
Applications go through National Grid's online nCAP (Customer Application Portal); the SIR requires electronic submission through the utility's portal, and hard-copy, email, or mailed applications are not accepted unless the portal is down. An optional pre-application report is available before formally applying.
| Track | Size | What review looks like |
|---|---|---|
| Expedited process | 50 kW or less | Six steps; completeness and eligibility determined within 10 business days. Inverter-based systems above 50 kW up to 300 kW certified to UL 1741 SB may also use this process. |
| Full process | Above 50 kW up to 5 MW | Eleven steps: preliminary screening (Screens A–F, results within 15 business days), optional supplemental screening (Screens G–I, 20 business days), CESIR study (60 business days), construction commitment, build, verification testing, interconnection, and cost reconciliation. |
| Utility process | Above 5 MW | Outside the SIR; separate National Grid process |
Massachusetts — DPU tariff pathways
Massachusetts applications also go through nCAP. The tariff sorts projects into three paths; customers unlikely to qualify for Simplified or Expedited may opt directly into Standard.
| Path | Typical projects | Review |
|---|---|---|
| Simplified | Listed inverter-based systems, 15 kW or less single-phase or 25 kW or less three-phase, on qualifying radial circuits (and certain small network systems) | Fastest path; the interconnection agreement is part of the application |
| Expedited | Listed facilities that pass pre-specified screens on a radial circuit | Screen review, with Supplemental Review if a screen fails |
| Standard | Everything else, including area-network projects that don't qualify for Simplified | Initial review, then Impact Study and Detailed Study as required |
Required forms & documents
New York (SIR): the SIR defines the complete application package in its appendices; National Grid layers its published technical requirements (ESB 756) on top. Structural contents:
- Standardized SIR application — inverter-based or non-inverter-based appendix form confirm current revision — submitted through nCAP
- SIR application-package checklist items (Appendix F confirm current revision)
- Customer authorization tied to the correct National Grid account and service point
- Single-line diagram; three-line detail where required for three-phase or storage designs
- Equipment spec sheets — inverters certified to UL 1741 (supplement SB) with settings per ESB 756
- Site plan
- Property-owner consent and site-control certification where applicable (SIR appendices)
- Energy storage systems: the ESS application requirements appendix (SIR)
- Verification-test paperwork at the end of the process
Massachusetts (M.D.P.U. No. 1599):
- Simplified Process application (tariff Exhibit A — includes the agreement) or Expedited/Standard application (Exhibit C) confirm current revision
- Pre-application report (Exhibit B) — optional below 250 kW, required at 250 kW and above for Expedited/Standard filings
- Interconnection Service Agreement for Expedited and Standard projects (Exhibit G)
- Single-line diagram and equipment spec sheets for listed inverters
- Landowner consent agreement where applicable (Exhibit I)
- Schedule Z — additional information required for net metering service
- Application fee payment per the tariff fee schedule
Fees
Two separate fee schedules. New York's comes from the statewide SIR; Massachusetts' comes from Table 6 of National Grid's DG tariff (M.D.P.U. No. 1599).
| State · Item | Published amount | Notes |
|---|---|---|
| NY · Application fee — 50 kW or less | None | The SIR requires no application fee for systems 50 kW or less |
| NY · Application fee — above 50 kW | verify current schedule | Set by the SIR and the utility's application page; applied per the SIR's cost-reconciliation rules |
| NY · Pre-application report | $750 verify current schedule | Per the SIR; non-refundable |
| NY · Supplemental screening | $2,500 verify current schedule | Non-refundable at election; actual costs up to $5,000 billable at reconciliation (SIR) |
| NY · CESIR study | Utility cost estimate | Invoiced before study start; project-specific |
| MA · Application fee — Simplified | $28 per application verify current schedule | Tariff Table 6; if the facility doesn't qualify for Simplified, the Company advises the appropriate fee |
| MA · Application fee — Expedited / Standard | $4.50/kW, minimum $300, maximum $7,500 verify current schedule | Tariff Table 6; covers screens |
| MA · Application fee — listed inverter on spot/area network | $100 (≤3 kW) / $300 (>3 kW) verify current schedule | Tariff Table 6 |
| MA · Supplemental Review | Up to 30 engineering hours at $150/hr ($4,500 maximum) | Tariff Table 6; Expedited path only |
| MA · Pre-application report | $100 (<250 kW) / $250 (250–500 kW) / $750 (>500 kW) | Optional below 250 kW, required at 250 kW and above |
| MA · Impact / Detailed Study, system modifications | Actual cost | Payment plan available when study costs exceed $25,000 |
Filing here every month?
Design partners get 5 free filings and their territory encoded first — packets produced with dual human review while the software is built.
Typical timeline stages
New York (SIR, business days): for systems 50 kW or less — application through nCAP, 10-day completeness and eligibility review, installation, verification testing, and final acceptance. For systems above 50 kW up to 5 MW:
- Application — complete package through nCAP; completeness response within 10 business days.
- Preliminary screening — Screens A–F; written results within 15 business days.
- Supplemental screening (if elected) — Screens G–I; completed within 20 business days of authorization and fee.
- CESIR (if required) — completed within 60 business days of authorization, fee, and complete design package; extendable by up to 40 business days by agreement.
- Contract, payment, construction, verification testing, and final acceptance — on the SIR's remaining clocks, with cost reconciliation at the end.
Massachusetts (M.D.P.U. No. 1599, business days): every path starts with a 3-day acknowledgment and a 10-day completeness review. The tariff's published maximum totals:
- Simplified — screens reviewed within 15 days (20 on a screen #5 failure); total maximum 25 days (30 with the screen #5 case). The agreement is part of the application.
- Expedited — screens within 25 days; Supplemental Review, if needed, 20 days; executable agreement within 10 days; total maximum 45 days (65 with Supplemental Review).
- Standard — initial review 20 days, Impact Study 55 days, Detailed Study 30 days, executable agreement 15 days; total maximum 135 days (160 if the application started in Expedited).
- Witness test — within 10 business days of the Certificate of Completion, or by mutual agreement.
Common deficiency causes
Common ways applications fall short of the published requirements above — each item maps to a requirement in the SIR, the Massachusetts tariff, or National Grid's technical documents. Not drawn from SunDocket filing data.
- Application package missing SIR appendix-checklist items — the New York completeness review is administrative and literal
- Filing under the wrong state's process or path — the two regimes share a portal brand but nothing else
- Single-line diagram missing detail at the point of common coupling, or three-line detail not provided where required
- Inverters not certified to UL 1741 SB, or certified but without the settings National Grid's technical requirements (ESB 756) specify
- Customer or site data that doesn't match the utility account of record
- Massachusetts filings at 250 kW or above submitted without the required pre-application report
- Wrong fee for the path — the Massachusetts fee schedule varies by path, size, and circuit type
- Missed response windows on deficiency notices, screening decisions, or agreement signatures, which can cost queue position
FAQ
How long does National Grid interconnection take in upstate New York?
The NYS Standardized Interconnection Requirements attach business-day clocks to each stage rather than one overall number. Systems 50 kW or less get a 10-business-day completeness and eligibility review; larger systems move through preliminary screening (results within 15 business days), optional supplemental screening (20 business days), and a CESIR study (60 business days, extendable by up to 40 by agreement). Actual end-to-end time depends on which stages a project triggers.
How long does National Grid interconnection take in Massachusetts?
National Grid's Massachusetts DG interconnection tariff (M.D.P.U. No. 1599, effective June 1, 2025) publishes maximum business-day totals per path: 25 days for the Simplified process (30 if a project fails screen #5), 45 days for the Expedited process (65 with Supplemental Review), and 135 days for the Standard process (160 if the application started in the Expedited process). Verify against the tariff revision in force when you file.
What is the National Grid interconnection application fee?
It depends on the state and path. In upstate New York, the SIR requires no application fee for systems 50 kW or less; larger systems pay an application fee and study fees per the SIR — verify current schedule. In Massachusetts, the tariff lists $28 per application for the Simplified process and $4.50 per kW (minimum $300, maximum $7,500) for the Expedited and Standard processes — verify current schedule.
What is nCAP?
nCAP is National Grid's Customer Application Portal — the online system where interconnection applications are submitted and tracked. New York's SIR requires electronic submission through each utility's online application portal, so hard-copy, email, and mailed applications are not accepted unless the portal is down.
What are the NYS Standardized Interconnection Requirements (SIR)?
The SIR is New York's Public Service Commission framework for interconnecting distributed generation and energy storage with an AC nameplate rating of 5 MW or less, aggregated on the customer side of the point of common coupling. It standardizes applications, screens, studies, fees, and timelines across the state's investor-owned utilities, including National Grid's upstate territory. The document current at review is effective February 9, 2026.
What is ESB 756?
Electric Service Bulletin 756 is National Grid's published technical requirements document for generation connected in parallel with its distribution facilities. Its Appendix B covers distributed generation connected under the New York SIR, and the bulletin also applies to National Grid's New England service areas. Designs and equipment settings are checked against it during review.
Does this page cover National Grid in Rhode Island or other states?
No. This page covers National Grid's upstate New York and Massachusetts electric distribution territories only. Other states and any gas-side processes are not covered here.
Change log
- Page created from public sources.
Requirements drift. Get the changes.
When this page's change log gets a new entry, we'll email you that entry. Nothing else — see the privacy note.
Sources
- NY Department of Public Service — NYS Standardized Interconnection Requirements (SIR document effective 2026-02-09) (accessed 2026-08-19)
- National Grid — Customer Application Portal (nCAP) (accessed 2026-08-19)
- National Grid — Pre-Application Report Request for Upstate NY Distributed Generation Projects (accessed 2026-08-19)
- NYSERDA — NY-Sun Interconnection resources (utility portal directory) (accessed 2026-08-19)
- National Grid — Standards for Interconnection of Distributed Generation, M.D.P.U. No. 1599 (Massachusetts, effective 2025-06-01) (accessed 2026-08-19)
- National Grid — ESB 756, Requirements for Parallel Generation (2024 supplement) (accessed 2026-08-19)
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