A draft final proposal of the California Independent System Operator (CAISO), titled "Large Load Enhancements," is dated September 24, 2026. It answers an order to show cause that the Federal Energy Regulatory Commission issued to the CAISO on June 18, 2026, one of six that went that day to the regional grid operators under the commission's jurisdiction. The proposal says it is offered "to establish new procedures for fast and reliable interconnection of new large loads." Parts of it follow, not the whole.
A large load, in the potential definition the CAISO puts forward, would be "An End User located at a single site whose Point(s) of Interconnection is/are to the CAISO-Controlled Grid," with "a peak load of 50 MW or greater." The CAISO says it may be premature to write a definition into its tariff while the North American Electric Reliability Corporation develops "similar, potentially overlapping, terms for computational loads."
On the grid under the CAISO's operating control, utilities, "specifically the PTOs, hold the lead role for load connections." A PTO, in a footnote of the proposal, is a party that has placed its transmission assets and entitlements under the CAISO's operational control. As a minimum standard, the CAISO expects the PTOs to develop consistent study procedures "to be completed within 60 to 90 days, as required by the Commission."
What FILI Would Offer
Alongside its "current generic firm service," the CAISO proposes a new Flexible Interim Load Interconnection service, FILI for short. It "would enable large loads to interconnect flexibly and receive service up to a certain level based on grid conditions and constraints until network upgrades are complete, at which time the large load would switch over to receiving firm service." Firm service would come when the upgrades are complete.
Where a PTO's proposed solution comes with network upgrades that have "an expected in-service date later than the large load interconnection date," it "would not be eligible to receive firm service until the network upgrade is placed into service." Such projects "would be candidates for the FILI process." So would a large load whose area network upgrades the CAISO's transmission planning process identifies the need for.
FILI "will likely be a tailored option for each large load based on its point of interconnection and the constraints it faces," and is "to be developed through a contractual agreement with the PTO." Some, the proposal says, may require little flexibility for a limited time, because there are few, less probable contingencies. Others may require more flexibility, because of transmission constraints that require network upgrades with longer timelines.
How a Load Would Be Held Back
On disconnecting large loads, the CAISO "does not envision direct physical disconnection of large loads by CAISO personnel," and expects any necessary load reduction or disconnection actions "to continue to be implemented through established coordination procedures between the CAISO and the applicable PTO or other responsible entity."
Depending on a large load's studies and its type of service, the CAISO and/or the relevant PTO may require further monitoring, control or protective systems, which "may include automated schemes designed to reduce or disconnect portions of the large load during abnormal system conditions." The CAISO "does not have direct control of switches, so the PTOs would need to make sure they have control at the right level."
For FILI itself, the service "may include a number of tools or measures, including but not limited to a Remedial Action Scheme (RAS), PTO operator curtailment, or managing to a present schedule." If a RAS is considered but "cannot be reliably operated, or is found to have significant market implications, the CAISO will not enable that option." To manage coordination of development of this interconnection service offering, the CAISO "will convene working groups with the PTOs, large load customers, and other interested stakeholders to maximize consistency and clarify roles and responsibilities."
No Cap, and Not for Supply Constraints
One stakeholder had supported a cap on FILI "to avoid it becoming a permanent substitute for needed transmission upgrades." The CAISO answers that it "is reluctant to place a one-sized-fits-all time limitation on what is intended to be a bespoke solution tied to the specific development timeline of the associated network upgrade," and that it "expects that the load will begin receiving transmission service as soon as the associated network upgrades are complete." It points to its Transmission Development Forum and other "statewide efforts to ensure timely completion of network upgrades as a means to track network upgrade completion and ensure continued progress." In its proposal it "declines to propose any kind of temporal or capacity cap on this interconnection service offering." With no cap on time, the interim would last as long as the upgrade takes. The date to watch would be the upgrade's in-service date, not the day the load connects.
The new service, the proposal says, "will enable faster interconnections while mitigating transmission constraints." It adds that "this interconnection service offering is not intended to address supply constraints."
Details for the PTOs to Develop
The CAISO agrees with one utility that the PTOs will offer the service, and "expects consistent implementation details across the PTO Tariffs." That utility listed the details it expected the PTOs to develop, and the CAISO "generally agrees" with its account of their responsibilities. The list includes "Cost responsibility provisions, including any financial security during the conditional service period," and "Transition-to-firm provisions for FILI that specify the automatic conversion to firm service upon network upgrade completion."
Two other stakeholders said that, while the offerings are intended to be customized, details such as "Curtailment triggers and operating conditions" and "How curtailment parameters will be established" would help. The terms that decide what the service is worth to a campus, how often it could be held back and what security it posts meanwhile, would be written later.
The CAISO will seek its Board of Governors' approval at the board's meeting of October 28, 2026.
Sources
- California Independent System Operator. Large Load Enhancements: Draft Final Proposal. 24 September 2026. grid operator