How NYISO Interconnection Works — Study Phases
1
Application & Queue Entry
Submit via NYISO's electric submission system. Deposit: $500K (≥20MW) or $100K (<20MW). Queue position assigned. Site control certification required. Projects grouped into annual Cluster Years (CY).
NYISO LGIP, Section 3.1
2
ATBA — Area Transmission Baseline Assessment
~3 months. Establishes the baseline grid conditions without the proposed project. No cost allocation at this stage. Required before any impact studies begin.
OATT Attachment S, §S-3
3
ATRA — Area Transmission Reliability Assessment
~3 months. Evaluates the project's reliability impact. Identifies thermal and voltage violations that must be mitigated. Determines System Upgrade Facilities (SUF) required.
OATT Attachment S, §S-4
4
DIS — Deliverability Interconnection Study
~6 months. The critical study. Determines whether the project achieves FCDS, PCDS, or Energy Only status. Identifies System Deliverability Upgrades (SDUs) shared across the cluster. C24 DIS identified $2.256B in SDUs across 92 projects.
OATT Attachment S, §S-5
5
SDU Election Window
30-day window after DIS results. Projects vote to fund shared SDU upgrades (Yes = proceed with ASDU, No = Energy Only or exit). C24: 57 Yes / 3 No elections. Declining projects lose CRIS eligibility.
OATT Attachment S, §S-6
6
ASDU & Interconnection Agreement
Additional System Deliverability Upgrade Study designs final SDU costs per project. IA negotiated with transmission owner (NYSEG, Con Ed, National Grid, or LIPA). Execution triggers construction milestones.
OATT Attachment HH, §40.3
Regulatory Framework
Governing Bodies
FERC + NYPSC Joint Oversight
FERC governs wholesale markets and interstate transmission under the Federal Power Act. NYPSC (NY Public Service Commission) oversees intrastate elements. NYISO administers the OATT and LGIP as a neutral grid operator.
Cluster Year System
Annual Cohort Studies
NYISO groups all applications from a calendar year into one Cluster Year (CY) for coordinated study. This prevents the serial queue problem that plagued other ISOs. CY23 ASDU finalized; C24 ASDU now in progress (57 projects). C25 cluster opens after C24 completion.
New Rules — 2024
OATT Attachment HH
Replaces Attachments S, X, Z for new projects from May 2024. Introduces structured cluster timelines, readiness deposits, and hard deadlines. C24 is the first cluster under HH. New SDU cost allocation methodology may substantially reduce costs for most projects except LI East and Zone J.
OATT Attachment HH — Active
Key Rights
ERIS vs CRIS
ERIS (Energy Resource Interconnection Service): right to inject energy — all projects receive this. CRIS (Capacity Resource Interconnection Service): required for ICAP capacity market participation. Must pass DIS or fund SDUs to obtain CRIS. CRIS is the primary revenue driver for storage projects.
Current Cluster Status
Feb 13, 2023
CY23 Study Commenced
ATBA base: 2028 summer peak. Includes CY21 accepted projects. Indian Point 2+3 retirements modeled. DEC Peaker Rule deactivations included.
May 16, 2024
CY23 Preliminary DIS — 11 Zone K Projects Failed
11 LI storage/solar projects failed the LI Byway no-harm test. Binding constraint: Pilgrim-West Bus 138kV PAR $295M. 10 elected Yes to ASDU.
Dec 12, 2024
CY23 ASDU Approved — $520.6M Allocated
SUF $104.4M + SDU $416.2M to PSEG-LI. Decision period opened Jan 13, 2025. 5 projects received final CRIS in Feb 2025.
Mar 2026
C24 DIS Presented — $2.256B SDU, 92 Projects
New Attachment HH methodology. 24 SDUs identified. Pilgrim-West Bus PAR $334M remains the binding LI East constraint.
Apr 2026
C24 SDU Elections — 57 Yes / 3 No
Hanwha Q CELLS and Arthur Kill II declined. 57 projects proceed to C24 ASDU study.
Now — 2026
C24 ASDU Study In Progress
57 projects. Final individual cost allocations being designed. New methodology may reduce costs for most projects outside LI East and Zone J.
2026 — TBD
C25 Cluster Opens
Timeline linked to C24 ASDU completion per Attachment HH Section 40.3.1.3.2.
Deliverability Status Types
Best Outcome
FCDS — Full Capacity Deliverability Status
Project can sell its full MW into the ICAP (Installed Capacity) market. Requires passing the DIS without triggering SDU upgrades, or fully funding required SDUs. Highest revenue potential. Required for bankable project financing in most cases.
Partial
PCDS — Partial Capacity Deliverability Status
A portion of the project's MW is deliverable as capacity; the remainder is energy-only. Common outcome where SDU costs are high relative to capacity revenue. Negotiated split between FCDS and energy-only MW.
Energy Only
Energy Only (EO)
No ICAP capacity revenue. Project sells energy only into the real-time and day-ahead markets. Avoids SDU costs entirely. Revenue limited — typically only viable for low-cost solar or storage with strong PPA offtake.