CAISO Cluster 16 Raised the Bar: How to Vet a POI in EPE’s InSights Platform Before You Commit

Three changes in this cycle have raised the stakes.

Why Does Your POI Choice Matter More in Cluster 16?

Site control now extends through Commercial Operation Date. Cluster 16 applications have to show control of at least 90% of the land the project reasonably needs, under agreements that extend through COD.

Intake scoring decides who gets studied. CAISO now scores applications on commercial interest, project viability, and overall system needs. Where zones are constrained, only the highest scoring projects proceed to the cluster study.

Fewer Points of Interconnection (POIs) are open. For Cluster 16, CAISO and participating transmission owners have restricted interconnection at a number of POIs due to short-circuit duty limits, proximity rules, physical space, or upgrades too complex to undertake. A substation that appeared viable last cycle may no longer be available to choose from.

Together, these changes mean fewer places to connect, longer site holds, and a higher bar to prove a project is viable. A POI with hidden upgrade costs or curtailment risk becomes harder to carry and harder to defend. Before committing to a site, developers need answers to a few basic questions.

• Is there actually room on the grid here?
• What transmission constraints could affect me?
• What other projects are competing for the same capacity?
• Could expensive upgrades kill the economics?

EPE’s InSights® platform releases its CAISO Cluster 15 results on Tuesday, October 6th. When you select a Cluster 15 result set, InSights shows hosting capacity for POIs open to Cluster 16. This allows you to rule out restricted sites immediately and spend your time on the ones you can actually connect to that have capacity for your project. From there, you can work through the remaining questions for each candidate POI. Keep reading to learn how to read and interpret the results.

Deliverability: Which Overloads Are Actually Yours?

InSights shows deliverability hosting capacity at a POI along with the overloads that limit it. But not every overload means the same thing, and the distinction determines whether you'd be responsible for the upgrade cost.

Know When to Care About Zero (“Pre-Existing”) Hosting Capacity Overloads: usually someone else's problem.

These overloads exist before your project is added. Earlier Cluster 15 projects caused them, and those projects are responsible for fixing them.

To check who's responsible in InSights, open the contributors for the overloaded element and look for Cluster 15 projects with a shift factor above 5%. If at least one is still active, responsibility stays with them. If all of them have withdrawn, remove their impact and recalculate. If the overload disappears, you have no responsibility for it. If it remains, it becomes yours.

Positive Hosting Capacity Overloads: likely yours, possibly shared.

These overloads occur because adding your project increases flow on a branch, so they're the ones you're most likely responsible for at this POI.

You may not carry the cost alone. In the contributors list, look for possible Cluster 16 projects with a shift factor above 5% on the same element. If those projects apply in this cluster, they'll share upgrade responsibility with you.

If shift factors are new to you, here's a primer on how developers use shift factor analysis to evaluate congestion.

When Do Older Interconnection Projects Withdraw from the Queue?

If a Cluster 14 or 15 project is labeled withdrawn in the contributors list, or has withdrawn since the data was released, its impact can be removed and the overload recalculated. If the overload disappears, so does your responsibility for it.

Reliability: Reading Curtailment Risk

Reliability results tell a different story. In CAISO reliability studies, overloads are typically managed through congestion management, so both Zero and Positive Hosting Capacity overloads can signal curtailment risk at your POI.

How much risk depends mostly on your POI's shift factors on the overloaded elements:

• Low shift factors across all overloaded elements: curtailment risk is generally minimal.
• High shift factor on one or more elements: review the other contributors. Resources with higher shift factors are typically curtailed first, so if yours is low compared to the biggest contributors, your risk stays low. If you're among the biggest contributors, your risk is higher.
• Other possible Cluster 16 projects: if they have higher shift factors than your POI on the same elements, they would likely be curtailed ahead of you if they join the cluster.

The same withdrawal logic applies here. If removing a withdrawn project's impact clears the overload, the curtailment risk from that overload goes away.

A Quick POI Check Before You Commit

For each candidate POI:

1. Review both deliverability and reliability hosting capacity in InSights.

2. Classify each overload as Zero or Positive Hosting Capacity.

3. Check contributors and shift factors to see who's responsible, who might share costs, and who gets curtailed first.

4. Account for withdrawn projects and recalculate.

5.Ask the bottom-line question: is this POI worth pursuing before you commit to the site? Factor in whether you can hold site control through COD and make a credible a strong intake scoring case.

Capacity view in InSights showing limiting elements and competing contributors.

What the Data Can and Can't Tell You

Hosting capacity results in InSights provide a general indication of deliverability and curtailment risk, not a final answer. Many inputs and assumptions can change the outcome, including withdrawals, new projects entering the cluster, and CAISO's own study assumptions.

Plan Around October 8

The Cluster 16 window opens October 1 and closes October 15 at 5 p.m. Pacific. CAISO has stated that applications submitted or corrected after 5 p.m. on October 8 likely won’t get another chance to fix deficiencies before the window closes, so treat October 8 as a priority deadline. Starting on October 6, run your POI checks in InSights and submit as early on October 8, as possible. If you need to file sooner, EPE’s interconnection team can support your application ahead of the release.

CAISO is raising the bar for which projects move forward. InSights lets you do the homework upfront, so your time and capital go to the sites most likely to make it. Then validate your top candidates with detailed engineering before you commit.

Fresh Cluster 15 results go live in InSights on Tuesday, October 6. Explore InSights for developers to review hosting capacity at your candidate POIs.