FERC Approves SPP’s CHILLS Tariff, Giving Data Centers Up to 7 Years of Curtailable Transmission

Federal energy regulators on June 5, 2026, approved a Southwest Power Pool tariff that lets data centers and other very large electricity users plug into the grid for up to seven years on interruptible transmission service, trading guaranteed delivery for a far faster connection. The order takes effect July 1, 2026.

What changed

SPP’s “Conditional High Impact Large Load Service,” or CHILLS, addresses a bottleneck that has stalled data-center connections across the operator’s 17-state footprint, which runs from northern Texas to Montana. Until now, a large load had to line up firm generation and the network upgrades to support it, a process that often takes years, before SPP would carry its power. CHILLS instead hands the customer non-firm service on whatever transmission capacity is already available, for a term of one to seven years, while it works toward permanent firm service.

Enforcement Reality

The speed comes with a hard condition: SPP will cut CHILLS customers off when the transmission system is constrained or under emergency conditions. A data center taking the service has to be willing to drop load on the operator’s command, and the arrangement expires after seven years whether or not firm service has materialized. FERC accepted the tariff subject to condition and gave SPP 30 days to file a compliance update under docket ER26-1323-000 (195 FERC ¶ 61,196).

The Seven-Year Clock

CHILLS turns the interconnection wait into a deadline. A data center gets non-firm service in months instead of the multi-year wait for firm generation and network upgrades, but the one-to-seven-year term is a countdown: the customer has to reach permanent firm service inside that window, and the arrangement expires at seven years whether or not firm service has materialized. That structure shifts the risk onto the load. SPP keeps the right to cut the customer off whenever the transmission system is constrained, so a data center betting on CHILLS is wagering that it will reach firm capacity, or absorb the curtailment, before the clock runs out. For a facility built to run continuously, interruptible service for up to seven years is a bridge, not a destination.

Why It Matters

CHILLS builds on SPP’s High Impact Large Load study processes, known as HILL and HILLGA, that FERC cleared in January 2026, and the operator is separately developing a Price Adaptive Load Service for customers willing to be curtailed on price. The approval lands as FERC pushes every U.S. grid operator to rewrite large-load rules. The commission issued show-cause orders to six regional transmission organizations on June 18, but SPP now has a working tool in place rather than a directive to design one. FERC called CHILLS “a just and reasonable and not unduly discriminatory or preferential approach” to connecting high-impact loads without undermining reliability.

Sources

• FERC — Order Accepting Tariff Revisions, 195 FERC ¶ 61,196 (Docket ER26-1323-000)
• Utility Dive — FERC approves SPP non-firm, large-load transmission service
• Energy Central — FERC greenlights SPP plan to offer data centers temporary transmission service

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