Data Center Site Selection in California and CAISO

The California Independent System Operator operates the high-voltage grid and wholesale energy market for most of California and a small part of Nevada. It also operates a real-time energy market that utilities across the West have joined. Not all of California is inside CAISO’s balancing area: several large municipal utilities operate their own balancing areas or sit within one outside CAISO, and they set their own large-load terms.

Inside CAISO, retail service is split among investor-owned utilities, municipal utilities and community choice aggregators. A community choice aggregator buys energy for customers in its area while the investor-owned utility continues to own the wires and handle interconnection. Direct access to competitive energy suppliers is limited. For a data center, that means the wires utility and the energy supplier can be different entities, and both matter.

California does not run a centralized capacity auction. Resource adequacy is handled through state programs: the state commission sets requirements for the load-serving entities it regulates, and municipal utilities set their own. Each load-serving entity must contract for enough capacity to cover its customers’ peak demand plus reserves.

The state also has long-standing clean-energy targets that shape what new supply looks like. New capacity tends to be solar, storage and other clean resources, and procurement runs on multi-year cycles. A large new load can therefore face questions about who procures its capacity and how long that takes, separate from the substation work.

Interconnection runs through the wires utility, which studies the load, scopes the substation and line work and coordinates with CAISO where the bulk grid is affected. Transmission service in the state is commonly at 115, 230 or 500 kV. CAISO plans transmission through an annual cycle, and major new lines in California take years to permit and build. Our guide to power timelines and interconnection queues explains why the realistic date matters as much as the capacity.

Load pockets near major metros can be tightly constrained, and transmission upgrades there often involve dense urban routing. Sites in the Central Valley or inland areas may have more room on the grid but less fiber and harsher summer heat.

The California Environmental Quality Act applies to discretionary approvals by state and local agencies. Depending on the project and the agency, review may be an exemption, a negative declaration or a full environmental impact report. CEQA documents are subject to legal challenge, which can extend timelines. A site that can be built under existing zoning with ministerial permits faces a different path than one that needs a rezoning or general plan amendment. See our guide to the data center permitting process.

• Local air districts permit diesel and gas backup generators and can set strict limits on testing hours and emissions. Rules differ by district.
• The state energy code includes efficiency requirements for computer rooms that affect cooling design.
• Coastal zone sites face additional review.
• Some agricultural land is under long-term conservation contracts that restrict development and take years to exit.

California’s hazard screen goes well beyond the floodplain map. Earthquake fault zones mapped by the state restrict construction across active faults, and seismic hazard zones flag areas prone to liquefaction and landslides. Wildfire hazard is mapped in fire hazard severity zones, and utilities may de-energize lines during high fire risk, which affects how much on-site backup a campus needs.

Drought is recurring, and water is a sensitive local issue. Groundwater use is subject to the state’s sustainable groundwater management framework, under which local agencies manage basins and can limit pumping. Many municipal systems offer or encourage recycled water for industrial cooling. Designs that use little water, such as air-cooled chillers or closed-loop liquid cooling, often have an easier path.

Climate varies widely. Coastal areas have mild temperatures that favor economization for much of the year. Inland valleys and deserts are hot in summer, which raises cooling loads and peak demand.

Land near the established data center markets is expensive and rarely available in large, contiguous blocks. Redevelopment of industrial and brownfield sites is common there. Larger tracts are more available inland, at the cost of distance from fiber hubs and, often, more complex agricultural and water issues. Fiber is strong in the major metros, with subsea cable landings along the coast and long-haul routes along the main interstate corridors.

1. 01Confirm the balancing area, the wires utility and the load-serving entity.
2. 02Ask who procures resource adequacy for the load and on what timeline.
3. 03Determine whether the project needs discretionary approval and what level of CEQA review is likely.
4. 04Check the local air district’s generator rules.
5. 05Screen fault zones, liquefaction, wildfire hazard and flood or levee exposure.
6. 06Confirm water source, groundwater basin status and recycled water availability.