Data center load growth in California could turn out to be “lumpy,” with sudden, large increases in specific regions of the state, rather than smooth growth over time.

Standard forecasting models assume smooth and diversified load growth, such as a 1.5% increase per year, GridLab Senior Program Manager Casey Baker said in a letter to the stakeholder working group managing CAISO’s large loads initiative. But data center load growth often jumps 50 to 100 MW almost instantly in specific locations, he said.

California’s data center demand is expected to increase by 1.8 GW by 2030 and 4.9 GW by 2040, but utility interconnection queues in the Silicon Valley area suggest the 4.9-GW demand could occur by 2030, Baker added.

To address sudden demand growth, CAISO should complete a high load-growth sensitivity case as part of its 2026/27 transmission planning process (TPP), he said. This study would show the risks of underbuilding the CAISO system compared to the risks and costs of overbuilding and would be particularly critical for the South Bay Area and other load pockets where growth is concentrated.

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Major transmission infrastructure requires eight to 10 years to plan, permit and construct, but modern data centers can be energized in two or three years. If CAISO’s TPP relies on the base case forecast but a high load-growth future occurs, the grid faces a physical deficit in the early 2030s that “cannot be remedied in time,” Baker said.

“The transmission owners simply will not be able to build wires fast enough to catch up to the demand,” he said.

A high load sensitivity case would include specific hot zones where loads develop at a higher rate than is currently forecast, Baker said.

“This is the only way to reveal where voltage instability and thermal overloads might occur that the base case forecast averages away,” Baker said.

GridLab cited a Silicon Valley Power (SVP) study that showed SVP’s capital construction plan far exceeds the state’s base assumptions. Load in Santa Clara will double from about 720 MW to about 1,300 MW by 2035, with most of it happening in the next five years.

It is important for CAISO to clarify how it will review large load interconnection requests, particularly when significant network upgrades are identified as needed, SVP representatives said in comments to CAISO on the initiative. These network upgrades could occur in utility-led load interconnection studies that are not fully reflected in the CAISO’s annual TPP, the representatives said.

SVP found that several 230- and 115-kV facilities could become overloaded based on proposed large load additions in SVP’s region, according to the letter.

CAISO does not presently have a threshold for what constitutes a large load, Danielle Mills, CAISO infrastructure policy development principal, said during a February CAISO workshop. (See CAISO Examines ‘Pulsating’ Data Center Loads.) The ISO is taking comments on this threshold and may develop a definition over the next several months.

Utilities are responsible for large load interconnections, but CAISO is monitoring developments at the federal level regarding whether RTOs and ISOs can or should be more heavily involved in the process, the ISO said in a Jan. 30 Large Load Considerations issue paper.

Large loads include more than data centers: Loads from EV charging stations and electric agricultural and industrial equipment, which also fall into the category, are expected to increase significantly over the coming years too.

SPP Model Should be Considered, Some Stakeholders Say

NextEra Energy representatives said CAISO should model SPP’s recent proposal for large loads that was approved by FERC. SPP’s proposal includes a 90-day study process for interconnecting large loads that will be paired with new local generation.

SPP’s model is “just and reasonable and not unduly discriminatory” and allows large load customers “to interconnect to the transmission system in a timely manner and increase the speed of interconnection queue processing,” NextEra said. CAISO could develop a similar model to meet the California Energy Commission’s large load forecast in a timely manner, it said.

CAISO could also develop a new way to study large load proposals in its interconnection queue, specifically those that include co-located generation, NextEra said.

Currently, large loads with co-located generators or energy storage facilities are part of two interconnection processes — the transmission owner’s load interconnection process and CAISO’s generator interconnection process. A more closely coordinated process is needed to ensure that large loads are quickly interconnected while recognizing the effects at the point of interconnection, NextEra said.