CAISO Will Let Large Loads Energize Before Network Upgrades Are Finished

The California Independent System Operator's Board of Governors approved a new framework on Oct. 28 for connecting very large electricity users to the state's transmission system, and the grid operator must file the tariff language with the Federal Energy Regulatory Commission by Nov. 16. The centerpiece is a service called Flexible Interim Load Interconnection, which lets a large load take service before the network upgrades it triggers are complete.

The filing answers a show-cause order FERC issued in June directing CAISO and five other regional grid operators, along with their transmission owners, to demonstrate that their procedures can absorb large loads quickly without compromising reliability or shifting costs onto existing ratepayers. That order also set a 60- to 90-day clock for transmission owners to finish load interconnection studies. The proposal the board approved defines a large load as 50 megawatts or more of peak demand at a single site. Pacific Gas and Electric asked for a 20-megawatt threshold and CAISO declined for now. A California Energy Commission forecast from January put data center load growth in the state at 1.8 gigawatts by 2030 and 4.7 gigawatts by 2035.

Interim service changes the sequence of the work more than its volume. Under the existing model, a data center or semiconductor fab waits for the area network upgrades identified in the transmission planning process before it energizes at all. Under the interim service, it energizes earlier and accepts enforceable operating restrictions set by grid conditions and transmission constraints until those upgrades are finished. The participating transmission owner identifies the local upgrades in its own interconnection study, and its tariff sets who pays for them. CAISO will also open a monthly window to review transmission additions tied to large loads that fall outside the annual planning cycle.

The framework writes operational visibility into the connection itself. Large loads will have to supply hourly forecasts, telemetry and other operational data, maintain communication channels with the transmission owner, and sit behind protocols that let CAISO coordinate remote disconnection when reliability demands it. That is metering, protective relaying, high-speed monitoring, fiber and controls scope, and it lands on the electrical contractor rather than the equipment vendor.

For commercial electricians working California's large-load pipeline, the practical effect is two mobilizations where there used to be one: a build-out sized to interim service, then a return when the permanent upgrade is energized. Phased work of that kind rewards crews comfortable with medium-voltage terminations, substation construction, and instrumentation and controls, and it puts a premium on certified general electricians who have logged relay and commissioning time rather than rough-in hours alone.

Whether any of it stands is FERC's call. The tariff language is due Nov. 16, and the commission's review will decide whether California's interim path survives as written. Until then, the queue in California still ends at the firm-service upgrades behind every one of these loads.