CAISO Interconnection at a glance
Quick facts | CAISO |
|---|---|
Who runs it | The California ISO runs the grid and generator interconnection studies for most of California. FERC approves its rules, and the CPUC oversees how utilities connect large loads. |
Governing rules | CAISO Tariff Appendix KK (Resource Interconnection Standards). For PG&E large loads, Electric Rule 30. |
Generator study process | One annual cluster, with applications accepted October 1–15. Requests are scored, and in Deliverable Zones only requests totaling up to 150% of available deliverability at each constraint are studied. |
Current cluster | The Cluster 16 window closed October 15, 2026. The Cluster Study is expected to start in January 2027. |
How competitive it is | In Cluster 15, 145 of 541 applications, representing 68 of 347 GW, made it into the study. |
Generator costs at application | A $5,000 non-refundable application fee, a study deposit of $150,000 to $250,000 for projects of 80 MW or more, and a commercial readiness deposit of twice the study deposit. The readiness deposit rises to 5% of network upgrade costs after the Cluster Study. |
Withdrawal penalties | They rise with each stage: 5% of network upgrade costs at reassessment, 10% at the facilities study, and 20% after signing, each at least the study deposit. |
Generator timeline | A 90-day engagement window, a 150-day Cluster Study and a 120-day facilities study, followed by deliverability allocation and the interconnection agreement. Commercial operation can be up to 7 years after the request. |
How large loads connect | Through the local utility. CAISO has no queue for loads, but it reviews utility studies and plans the network upgrades behind them. |
Large-load threshold | CAISO’s Board-approved proposal defines a large load as one site on the CAISO grid with 50 MW or more of peak load. It’s pending at FERC. |
Large-load rules status | CAISO’s Board approved its large-load proposal on October 28, 2026, including a Flexible Interim Load Interconnection service. CAISO will file it with FERC by November 16, 2026, and it takes effect only after FERC accepts it. PG&E’s Rule 30 is still interim, pending a final CPUC decision. |
Peak demand, for scale | 50.0 GW on September 9, 2026, below its record high of 51.1 GW reached on September 6, 2022 |
Last updated | November 3, 2026 |
CAISO Generator Interconnection Process
Generator interconnection,
step-by-step
CAISO studies generators in one annual cluster, but only after scoring them, and only the top scorers in each zone are studied. Withdrawal penalties rise at each stage.
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Check deliverability and point of interconnection data. By September 1 each year, CAISO publishes how much deliverability is available in each transmission zone. It also keeps a public heatmap of available injection capacity at each POI.
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Apply during the October window. Submit through CAISO’s GRIP portal from October 1–15, with technical models, at least 90% site control and all deposits. Incomplete applications can’t be fixed.
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Scoring. Requests are scored on commercial interest, project viability and system need. In Deliverable Zones, only requests totaling up to 150% of available deliverability are studied.
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Customer engagement window. Over 90 days, CAISO validates data and confirms each project’s point of interconnection, and developers sign a Cluster Study Agreement.
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Cluster Study and readiness deposit. CAISO studies grid impacts and upgrade costs over 150 days. To stay in, developers raise their readiness deposit to 5% of network upgrade costs.
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Reassessment and facilities study. CAISO restudies the cluster each year, then finalizes costs in a 120-day facilities study. Projects whose upgrade costs pass set thresholds can withdraw without penalties.
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Deliverability allocation and agreement. CAISO allocates deliverability, with priority for projects with signed power contracts, and the developer signs the interconnection agreement.
CAISO Large Load Interconnection Process
Large Load interconnection,
step-by-step
CAISO has no queue for large loads. Data centers connect through their utility, under rules set by the CPUC, while CAISO reviews the utility’s studies and plans the network upgrades behind them. Both CAISO’s large-load rules and PG&E’s new tariff are still pending, so confirm current requirements.
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Apply to your utility. Contact the utility that serves the site, such as PG&E, SCE or SDG&E. Smaller loads connect at distribution voltage under the utility’s standard rules.
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Follow your utility’s large load process. In PG&E territory, where most of California’s data center growth is concentrated, transmission-level loads apply under Electric Rule 30, which has been in interim use since July 2025. Other utilities follow their own processes.
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Utility load study. The utility studies the connection and any upgrades. CAISO’s approved proposal supports a 60–90 day timeframe for these studies, with CAISO reviewing new requests monthly.
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Fund the connection. Under PG&E’s Rule 30, customers pay upfront for the connection and nearby facilities. They also take on minimum demand charges and termination fees if service ends early.
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Transmission planning. Larger network upgrades are built through CAISO’s annual Transmission Planning Process, which studied 4.5 GW of data centers in its latest plan. Requests between planning cycles would get a monthly review under CAISO’s approved proposal.
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Sign agreements and build. The customer signs service and facilities agreements with the utility, which builds the connection.
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Energize. The utility energizes the load once its facilities and any required upgrades are in place.
What's changed recently in CAISO interconnection
Last updated November 2026
CAISO’s generator process is running its second scored cluster, and the rules for large loads are being written at both FERC and the CPUC. If your project is in CAISO’s process or headed there, check which of these changes apply before your next deadline.
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July 2025: The CPUC approved interim use of PG&E’s Electric Rule 30, a standard tariff for transmission-level loads, with customers paying upfront for the infrastructure they need.
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May 2026: PG&E and several parties asked the CPUC to approve a partial settlement on Rule 30. A final CPUC decision hasn’t been issued.
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June 18, 2026: FERC opened a proceeding on large and co-located loads in CAISO. CAISO later asked FERC to pause it while CAISO finished its own large-load rules.
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August 4, 2026: FERC ruled on CAISO’s latest interconnection process changes, and accepted CAISO’s compliance filing on September 30.
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October 15, 2026: The Cluster 16 application window closed, and CAISO posted a Cluster 16 queue report the next day.
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October 28, 2026: CAISO’s Board approved its large-load proposal, including a Flexible Interim Load Interconnection service that lets large loads connect before network upgrades are complete, and a new monthly window to review transmission additions tied to large loads outside the usual planning cycle, supporting 60–90 day utility load studies.
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Coming up: Tariff filings at FERC from CAISO and the utilities on November 16, 2026, the start of the Cluster 16 study in January 2027, a new initiative on permanent flexible connections in the first half of 2027, and a final CPUC decision on Rule 30.
How LandGate Helps with CAISO Interconnection
Quickly and accurately determine the feasibility of a site in CAISO using LandGate's nationwide data
Get your projects on the grid faster with reliable transmission data.
Pick a strong site before October
CAISO’s application window lasts only 15 days, and applications need at least 90% site control, so site selection has to happen months ahead. Search parcels by criteria such as distance to a substation and available offtake capacity, and see available transfer capacity at transmission-level injection points to find POI's worth applying for.
Know your upgrade exposure
Once the Cluster Study is done, withdrawal penalties climb from 5% to 10% to 20% of network upgrade costs. LandGate’s automated offtake capacity studies show substation details, capacity results, limiting elements such as transmission lines, and queue information, so you can spot upgrade risks before you're locked in.
Find the right substation
In CAISO, a data center starts with its utility, and under PG&E’s Rule 30 the customer pays upfront for the connection and nearby facilities. Landate's Data Center Due Diligence Reports identifies the ISO, the nearest transmission lines, and ranks the closest substations by capacity so you can target sites requiring less infrastructure.
Lock down the best sites
CAISO requires proof of at least 90% site control at application, with no chance to fix an incomplete one. LandGate pairs its grid data with proprietary landowner leads, nationwide ownership data, and a map-based CRM to help you find and secure the right parcels, including off-market properties with the right infrastructure profile.
