The CESIR, explained.
Before a battery or a solar array can connect to a National Grid feeder in New York, the utility studies it. That study is the Coordinated Electric System Interconnection Review.
Start the tourJump to the costA safety study of the wire.
The utility models the feeder with your battery on it: fault current, relay coordination, voltage, thermal loading, power quality (SIR Step 6, p. 11).
See the diagramMore than $12,000. No ceiling.
Probably more than $12,000 on the low end. National Grid's filing shows one flat figure for every size band from 500 kW to 5 MW, which reads as a floor, not an average (Joint Utilities, 2022). The fee itself is "project-specific" and its makeup "proprietary" (National Grid, 9/9/2026).
Try the sliders115 to 185 Business Days.
About five to nine months from a complete application to the CESIR report, adding the SIR's utility clocks end to end (SIR pp. 6 to 11). ESTIMATE
Watch the raceA safety study of the wire you want to plug into.
The New York Public Service Commission defines it in one sentence:
Any studies performed by utilities to ensure that the safety and reliability of the electric grid with respect to the interconnection of distributed generation as discussed in this document.NYS Standardized Interconnection Requirements (SIR), effective February 9, 2026, Section III Glossary, p. 32
National Grid describes its own version this way:
The intent of the CESIR is to assess the project's feasibility, determine its impact on the utility's EPS, determine interconnection scope and installation requirements, and determine costs associated with interconnecting the Interconnection Customer's generation to the Company's EPS.National Grid, ESB 756 (2024, Version 9.0), Section 5.3(H), p. 15. EPS = Electric Power System.
What the study looks at, drawn the way an engineer draws it: utility source, substation transformer, 4.8 kV bus, feeder breaker, recloser, point of common coupling, customer transformer, inverter, battery. Symbols after IEEE 315 / ANSI Y32.2 conventions.
Sources: SIR, Case 24-E-0621, dps.ny.gov; National Grid ESB 756 Supplement to Specifications for Electrical Installations 2024.
What it checks
Whether the project causes "any protective coordination, fault current, thermal, voltage, power quality, or equipment stress concerns."
SIR Step 6, p. 11 · click for the full list
What it returns
Six written items, including "a good faith, detailed estimate of the total cost" with contingency capped at 15 percent, and a Qualifying Upgrade Disclosure.
SIR Step 6, p. 11 · click for all six
Who does it
The utility. National Grid says each project "is studied individually, and requirements are identified independent of previous studies."
National Grid written answers, 9/9/2026 · click for the quote
Who it is for
Any generator or battery above 50 kW and up to 5 MW that fails the simple screens. Under 5 MW, "you are only required to go through the NY State SIR process."
SIR Section I.C; National Grid, 9/9/2026 · click for detailCard illustrations generated for this page on 9/11/2026 (kie.ai); they illustrate concepts only.
Hover a card. Each one flips to the answer.
Why can't I just connect?
A feeder is built for power flowing out from the substation. A battery pushes power back. Protection that was never designed for reverse flow can fail to see a fault. The SIR requires the utility to check this before any parallel operation (Section II, Design Requirements).
Why does it cost money?
Because the rules put the study on the applicant. National Grid: "As allowed by the NY SIR and the Company's Electricity Tariff, the costs of the detailed study and upgrades are the responsibility of the IC." (ESB 756, 5.3(G), p. 15)
Why not skip to a quote?
The utility will not price upgrades without the study. National Grid: protection cost "is different from project to project and will be provided when the CESIR Study has concluded." (written answers, 9/9/2026)
Why does it take months?
The SIR gives the utility 60 Business Days for the study itself, plus up to 40 more by agreement, after the screening clocks. Every clock in the SIR runs in Business Days, not calendar days. (SIR pp. 7 to 11)
Sources: SIR effective 2/9/2026; National Grid ESB 756 (2024) p. 15; National Grid written answers on the Mexico Auto-DLM questions, 9/9/2026.
Eleven steps. The CESIR is three of them.
Hover a number for what happens there. Click it for the full rule. Section I.C of the SIR governs systems above 50 kW up to 5 MW; a battery adds one storage review in Section I.E.
Source: SIR effective 2/9/2026, Section I.C pp. 6 to 13, Section I.E p. 17; application fee per National Grid written answers, 9/9/2026. BD = Business Days.
Move the sliders. The fees update live.
Utility fees only, from the application to the CESIR report. Your own engineering hours are extra. ESTIMATE
1. The capped fees
2. What makes the CESIR itself cost more
These are the twelve items National Grid marked in the Joint Utilities' cost-driver filing (2022, page 2). Slide each from simple to complex. The filing names the drivers but prices none of them. National Grid's filing shows one flat figure for every size band from 500 kW to 5 MW, so it reads as a floor, not an average; call it more than $12,000 on the low end. There is no published ceiling. These sliders run the fee from $12,000 with everything simple to $200,000 with everything complex; the top end is an illustration of how far an uncapped fee can go, not a published figure. ESTIMATE
National Grid on 9/9/2026: the CESIR fee "is project-specific and will be determined once the application has been processed," and its itemization is "proprietary." Probably more than $12,000 on the low end.
The fee is small. The answer can be large.
The CESIR report prices the utility's upgrades. At a substation with no backfeed protection, that can mean zero-sequence overvoltage (3V0) protection, relays and reclosers. National Grid's own planning guide priced substation 3V0 at $250,000 to $350,000 below 69 kV (Joint Utilities ITWG Technical Guide Matrix, 12/13/2016). ESTIMATE
What softens it: substation upgrades that add hosting capacity are cost-shared pro rata, "whereby the applicant pays only for the specific distribution hosting capacity assigned to its project" (SIR Appendix E, p. 2), and every advance is reconciled to actual cost at Step 11 (SIR pp. 12 to 13).
Sources: SIR Appendix E and Step 11; Joint Utilities ITWG Technical Guide Matrix 2016, DPS DocRefId AB571924.
Two races to the same report.
The SIR's utility clocks, added end to end. Watch the runner. Hover a segment for the rule behind it. Your own time to assemble the Step 5 package is not counted. ESTIMATE
Source: SIR effective 2/9/2026. Completeness review 10 BD (p. 6); preliminary screening 15 BD (p. 7); applicant notice 10 BD (p. 7); supplemental screening 20 BD plus 10 BD notice (pp. 8 to 9); CESIR invoice 10 BD and payment 10 BD (p. 8); CESIR 60 BD plus up to 40 BD by agreement (p. 11). Month ticks at 21.5 Business Days each.
The applicant. In National Grid's own words.
As allowed by the NY SIR and the Company's Electricity Tariff, the costs of the detailed study and upgrades are the responsibility of the IC.
National Grid, ESB 756 (2024, Version 9.0), Section 5.3(G), p. 15. IC = Interconnection Customer.In the event final charges are greater than the CESIR estimate, the Interconnection Customer will be responsible for all final charges. In the event the final charges are lesser than the CESIR estimate, the Company will reimburse excess charges.
National Grid, ESB 756 (2024, Version 9.0), Section 5.5(A), p. 17The interconnection application fee is currently $750.00 but the CESIR Study Fee is project-specific and will be determined once the application has been processed.
National Grid, written answers on the Mexico Auto-DLM questions, 9/9/2026National Grid does not provide this information to any applicants as our process is proprietary.
National Grid, written answers, 9/9/2026, on itemizing the CESIR feeNo ceiling
Neither the SIR nor ESB 756 sets a maximum CESIR fee. National Grid calls it "project-specific." Maximum: UNCONFIRMED.
Two fees the SIR does cap
Supplemental screening at $5,000 (p. 8). Storage Protection and Control Review at $3,000 (p. 17). Everything else is uncapped.
Sources: National Grid ESB 756 (2024, Version 9.0) pp. 15 and 17; National Grid written answers, 9/9/2026; SIR effective 2/9/2026 pp. 8 and 17.
Not sure how big the battery will be? Study the big one.
The SIR has no change order. Ask for more than 2 percent above what you filed and it is a Material Modification: a new application, a new queue position, and the study starts over at your cost, on a new clock (SIR pp. 20 and 33). Set your odds below and see which filing costs less.
An increase in the nameplate kVA or kW rating of the originally proposed distributed generation facility or energy storage system of more than 2%.SIR, Glossary, definition of Material Modification, item 3, p. 33
A Material Modification to a project will require a new application, a new queue position, and removal of the original application if the applicant elects to move forward with the modification (if not yet interconnected).SIR, Section I.H Modifications, p. 20
A change reducing the AC output or nameplate rating of the generating facility.NYS DPS Staff, DER Material Modifications: Guidance Document, listed under non-material modifications
Sources: SIR effective 2/9/2026, Section I.H p. 20 and Glossary p. 33; DPS Staff DER Material Modifications guidance, 2022. Fee arithmetic uses the $750 application fee (National Grid, 9/9/2026), the $3,000 storage review cap (SIR p. 17) and $12,000 as the low end of the CESIR fee (National Grid's filing shows the same figure for every size band; Joint Utilities, 2022). A second application also restarts the clocks on this page: about 115 Business Days at the fastest. ESTIMATE.
The report is the key to everything after it.
The upgrade price
"a good faith, detailed estimate of the total cost" broken down by equipment, material, labor and overhead. Contingency capped at 15 percent.
SIR Step 6, p. 11
The contract
The New York Standardized Interconnection Contract follows the report. Above $10,000 of upgrades: 25 percent within 90 Business Days, then 75 percent within 120.
SIR Step 7 and Section I.D, pp. 11 to 14
Cost sharing
The Qualifying Upgrade Disclosure tells you which substation work is shared pro rata with later projects, and refundable.
SIR Step 6, p. 11; Appendix E
The design
Relay settings, control-system changes and site-specific test procedures that the installation must meet before parallel operation.
SIR Steps 6, 9 and 10, pp. 11 to 12
Source: SIR effective 2/9/2026.
Every acronym on this page.
Coordinated Electric System Interconnection Review. The utility's study (SIR p. 32).
New York State Standardized Interconnection Requirements, effective February 9, 2026.
Business Days. Every SIR clock counts Business Days.
Interconnection Online Application Portal. Required for filing (SIR p. 6).
Energy Storage System. A battery.
Distributed Energy Resource / Distributed Generation.
Point of Common Coupling. Where your wiring meets the utility's.
Electric Power System. National Grid's term for its grid (ESB 756).
Interconnection Customer. The applicant (ESB 756).
Zero-sequence overvoltage protection at the substation (SIR Appendix E).
The inverter safety standard, supplement B.
National Grid Electric System Bulletin 756, its parallel generation specification, 2024, Version 9.0.
Where every number and quote comes from.
- New York State Public Service Commission. New York State Standardized Interconnection Requirements and Application Process for New Distributed Generators and Energy Storage Systems 5 MW or Less, effective February 9, 2026, Case 24-E-0621. dps.ny.gov PDF. Read 9/11/2026. Page numbers are the document's printed page numbers.
- National Grid. ESB 756, Supplement to Specifications for Electrical Installations 2024, Requirements for Parallel Generation Connected to a National Grid owned EPS, Version 9.0. nationalgridus.com Electric Specifications. Quoted for who pays (5.3(G) p. 15), the purpose of the CESIR (5.3(H) p. 15) and reconciliation (5.5(A) p. 17).
- National Grid. Written answers on the Mexico, New York Auto-DLM interconnection questions, 9/9/2026 (file Mexico_AutoDLM_Questions_for_NationalGrid_Responses_9-9-26.docx). Quoted for the $750 application fee, the project-specific CESIR fee, the proprietary itemization, protection cost timing, and the under-5 MW process.
- Joint Utilities of New York. CESIR Cost Drivers matrix, 2022. dps.ny.gov PDF. Page 2 for the twelve National Grid cost drivers; page 5 for the fee figure from 2018 to 2019 studies, the same in every size band and "not size dependent," read on this page as a low end of more than $12,000.
- NYS DPS Staff. DER Material Modifications: Guidance Document, 2022. dps.ny.gov DOCX. Quoted for the 2 percent rule and for reductions being non-material.
- Joint Utilities ITWG. Technical Guide Matrix, 12/13/2016, DPS DocRefId AB571924. Cited for National Grid's 3V0 cost range, $250,000 to $350,000 below 69 kV. ESTIMATE.
- Diagram and images. The one-line diagram is drawn for this page with IEEE 315 / ANSI Y32.2 style symbols. The hero, cost and four card illustrations were generated for this page on 9/11/2026 (kie.ai, nano-banana-2). They illustrate concepts and are not photographs of any site.