CAISO Interconnection Process — Step by Step
1
Application & Feasibility
Submit via CAISO Queue Management System. $150k deposit for Large Gen (>20 MW). CAISO confirms cluster assignment within 5 business days.
CAISO Tariff, Appendix DD
2
Phase I — Interconnection Feasibility Study
Cluster study. Screens thermal, voltage, and stability impacts. Identifies potential Network Upgrades at high level. 180-day study window. Cost ~$350k shared among cluster.
CAISO BPM-CG-012, Section 7
3
Phase II — Interconnection Facilities Study
Detailed engineering. Firm interconnection costs identified. TPD (Transmission Planning and Deliverability) assessment included. 300-day study window.
CAISO BPM-CG-012, Section 8
4
Interconnection Agreement (GIA)
30-day execution window after Phase II results. FERC filing required for Large Gen. Network Upgrade cost responsibility allocated. IFS (Interconnection Financial Security) posted at signing.
CAISO Tariff, Appendix DD §17
5
Readiness Milestones (M1–M5)
Five milestones per FERC Order 2023: M1 (site control), M2 (permit filing), M3 (permit received), M4 (IFS increase), M5 (commercial operation). Failure triggers automatic withdrawal.
FERC Order 2023, §35.28(f)
6
Commercial Operation
NTP (Notice to Proceed) issued by CAISO after all milestones complete. As-built drawings filed. Revenue metering tested. Final settlement of study cost actuals vs. estimates.
CAISO BPM-CG-012, Section 11
Active Queue Clusters
In Progress
Cluster 14 (2023–2025)
Approximately 70 GW applied across ~1,400 projects. Phase I studies underway. Heavy solar + storage mix. NUC cost estimates expected Q2 2025. Largest cluster in CAISO history.
Phase I → Q2 2025
Pre-Application Open
Cluster 15 (Open 2024)
Pre-application window open since Q4 2024. First cluster expected to include offshore wind from Morro Bay and Humboldt Bay. CAISO developing new offshore interconnection framework.
Applications Open → 2025
Reassessment
Cluster 13 Reassessment
43 projects (~28 GW) in reassessment after Phase II results. High NUC costs ($180–250k/MW range) drove significant withdrawals, triggering mandatory reassessment under CAISO tariff.
Post Phase II Withdrawal Trigger
Fast Track
Small Gen Queue (≤20 MW)
Projects under 20 MW capacity use fast-track 60-day study process. Primarily rooftop-adjacent solar, small storage, and behind-the-meter co-generation projects.
CAISO Tariff, Appendix Y
FERC & California Policy Context
Federal
FERC Order 2023 (May 2023)
CAISO filed compliance tariff January 2024. Readiness milestones M1–M5 replace deposit-based queue discipline. Cluster re-study triggered automatically if >15% of MW withdraws after Phase I. Standardizes GIA terms across RTOs.
FERC Docket RM22-14
State — 2022
AB 205 — RA Centralization
Centralizes Resource Adequacy procurement through CPUC. Directs load-serving entities to procure 15% reserve margin above peak demand. Drives demand for FCDS-eligible storage interconnections throughout CAISO footprint.
CPUC R.21-10-002
State — 2018
SB 100 — 100% Clean by 2045
Mandates 100% clean electricity by 2045. CAISO Long-Term Procurement Plan models 85 GW solar, 20 GW offshore wind, and 50 GW storage needed by 2045. Drives LTPP transmission expansions already underway.
PRC §399.11 et seq.
Tracking
WREGIS Certificate Tracking
Western Renewable Energy Generation Information System tracks RECs for all CAISO generation. Bundled RECs (delivered to CA) vs. unbundled (sold separately) carry different RA compliance value under CPUC rules.
WREGIS Operating Rules v6
Recent Regulatory Timeline
January 2024
CAISO filed FERC Order 2023 compliance tariff
Submitted revised interconnection procedures adopting readiness milestones M1–M5, updated cluster re-study triggers, and standardized GIA terms. FERC accepted with modifications April 2024.
April 2024
Cluster 14 Phase I kicked off
Over 1,400 project applications processed into Cluster 14. CAISO issued cluster groupings based on shared network upgrade scope. Largest cluster by MW ever processed by CAISO.
July 2024
CPUC D.24-06-055 — RA storage counting rules confirmed
Decision confirmed 4-hour minimum discharge duration for storage to count toward RA. Clarified deliverability requirements for FCDS vs. PCDS storage resources. Significant for battery queue projects.
January 2025
Cluster 14 Phase I results released
Estimated Network Upgrade Costs distributed to Cluster 14 participants. Projects evaluating whether to advance to Phase II based on NUC allocation. Expected significant attrition (~30–40% withdrawal rate).
Q3 2025
Cluster 14 Phase II begins
Projects clearing Phase I and posting required deposits begin detailed Interconnection Facilities Study. CAISO targeting 300-day completion window for individual project cost determination.
2026
First CAISO offshore wind interconnection studies
Humboldt Bay floating offshore wind interconnection studies commence. CAISO developing new offshore study methodology — no precedent in CAISO tariff for HVDC-linked floating OSW resources.