FERC Sets June 2026 Deadline to Rewrite Large-Load Grid Rules

On April 16, FERC issued a two-sentence order that will reshape how gigawatts of new industrial power demand flow into the U.S. transmission system. The Federal Energy Regulatory Commission set a hard deadline to act by the end of June 2026 on rules governing how large loads over 20 megawatts interconnect to the interstate transmission grid — a decision that sounds technical but is actually about who pays billions in infrastructure costs and, by extension, whether new data centres and factories get built in the first place. The order, filed in docket RM26-4-000, came after FERC staff reviewed more than 3,500 pages of public comments and held what the commission describes as 'numerous meetings with stakeholders.' This is not an aspirational target. FERC said it 'intends to act' by June 30, meaning the final rule is now a regulatory commitment with real deadlines flowing backward through grid operators and investor planning cycles.

Here is why this matters more than the format suggests. The U.S. electrical system built over the last 70 years was designed for a different load profile: steady demand from cities, peaking in summer, with predictable industrial baseload. Data centres are changing that. They drove a 22 percent increase in overall U.S. electricity demand in 2025 and could triple by 2030, according to data the brief cites from government and market sources. But data centres are not like a steady-state factory. American Transmission Co., which operates one of the nation's largest transmission systems, notes in its submission to FERC that new AI data centres have 'extreme operating variability' — they can ramp load up and down by hundreds of megawatts in seconds, 'equivalent to turning Wisconsin's capital city of Madison on and off, repeatedly.' The grid does not have the transmission lines to handle this, and building them is not cheap. A single major transmission corridor can cost $1 billion to $3 billion and take seven to ten years to permit and construct. The question FERC is answering by June is: who pays for those lines?

The April 16 order did not reveal FERC's final position, but it telegraphed the likely direction. FERC has already adopted a 100 percent participant funding model in two pilot programs — one with PJM Interconnection in December 2025 and another with Southwest Power Pool in January 2026. Under this approach, large load customers pay the full cost of network upgrades their projects trigger. That is a clean break from the traditional model, where transmission costs are socialized across all ratepayers. The Energy Department's Energy Secretary Chris Wright had originally set an April 30, 2026 deadline for FERC to act. FERC's April 16 order essentially asks for two more months, committing to deliver by June 30 instead. The extension signals that the commission knows this rule will be legally contested and wants to get the reasoning airtight. FERC explicitly stated it intends to address DOE's October 2025 directive 'in a manner that is quick, efficient, and legally durable.' Durable is the key word — this rule will likely end up in federal court, probably within weeks of issuance.

The mechanics of the rule are already partially in place. In December 2025, FERC required PJM to implement three new transmission service options for large co-located customers and revise cost allocation rules to curb cost-shifting to smaller loads. In January 2026, FERC approved Southwest Power Pool's High Impact Large Load initiative, which fast-tracks data centre interconnections by requiring applicants to use co-located generation (solar, wind, or small nuclear) alongside their load and allowing the utility to avoid paying for some transmission upgrades. On April 1, 2026 — less than three weeks ago — SPP completed an expansion of its service territory into the Western Interconnection, becoming the only regional grid operator spanning two of the three major interconnections. That expansion gives SPP direct control over transmission across portions of seven additional states: Arizona, Colorado, Montana, Nebraska, New Mexico, Utah, and Wyoming. The timing is not coincidental. SPP refiled its Conditional High Impact Large Loads Service proposal on February 10, expecting FERC approval by mid-April with a July 1 effective date. That deadline passed. FERC's response is imminent and will be the first real test of how the June rulemaking applies in practice.

The rule's direct beneficiary is clear: data centre developers and the equipment manufacturers that power them. A developer that gets the FERC stamp of approval for a 200-megawatt load paying 100 percent of transmission costs knows exactly what that bill is upfront. The surprise is that this certainty itself is valuable. Right now, large loads face open-ended interconnection queues and ambiguous cost allocation rules that differ by region. That ambiguity kills projects. Once FERC standardizes the rule, the cost is fixed, and capital flows. Projects that were economically marginal become viable because developers no longer face the risk of a surprise $200 million transmission bill after two years of permitting. The losers are less obvious but just as real. First, existing ratepayers in regions with heavy new data centre deployment — particularly the Midwest and Texas, where PJM and ERCOT operate — will see smaller transmission cost increases than they would under the old socialized model. But second, and more important, smaller industrial loads and distributed generation will find it harder to interconnect. If large loads capture all the transmission capacity they need by paying for it directly, the remaining capacity gets more expensive for everyone else. Regional transmission operators will have less flexibility to cross-subsidize smaller players. This is a winner-take-most outcome, and FERC knows it. That is why the rule is legally durable in the short term but politically vulnerable in the long term.

What FERC is actually doing is resolving a tension that has been building for two years. The traditional transmission cost allocation model assumes that loads are stable and that the grid operator has flexibility to upgrade capacity for multiple users at once. Both assumptions are broken. Data centres are volatile, and transmission bottlenecks are acute. A participant funding model solves the short-term problem by making cost allocation transparent and creating incentives for large loads to co-locate with generation. But it does so by externalizing the problem onto smaller players. The June rule will codify that choice. FERC will essentially be saying: the grid is constrained, new loads are volatile, and we are going to let large loads that can pay for upgrades move to the front of the queue. Smaller industrial customers and distributed solar projects will go to the back or find other regions. This accelerates data centre deployment in the Midwest and Southwest but potentially slows electrification in rural and underserved areas where transmission capacity is scarcer and larger loads are rare. FERC's June rule is not really about large-load interconnection at all. It is about deciding which parts of the country get to grow and which do not.

The June 30 deadline is firm, but what comes after is predictable. Within weeks of the rule being issued, state utility commissions, small manufacturers, and rural co-ops will file briefs in the U.S. Court of Appeals arguing that FERC exceeded its jurisdiction and violated the Federal Power Act's requirement that utility rates be 'just and reasonable.' That is a real legal argument, and FERC knows it. The commission's April 16 language about acting in a 'legally durable' manner is code for: we are going to write this opinion so carefully that even if we lose in court, it takes three years and two appeals to overturn it. By then, the rule will have been in place long enough that reversing it creates even more disruption. That is how regulatory combat works at this level. The actual winner is not data centre operators, though they benefit. The actual winner is the grid operator that manages large loads well and builds transmission capacity efficiently. That is Southwest Power Pool, which now operates across two interconnections and has a first-mover advantage in the data centre interconnection space. PJM is second. The traditional utilities — American Electric Power, Duke Energy, Southern Company — will have to fight for data centre loads in their own territories and will likely lose some to SPP regions where costs are lower. That is the real story FERC's June rule will tell.

Watch three things to know if this plays out as described. First, SPP's CHILLS proposal decision from FERC should come within days. If FERC approves it with an effective date before June 30, the June rulemaking will essentially codify SPP's model nationally and FERC just made the Southwest the preferred region for data centre deployment. Second, follow PJM's compliance filing deadlines. FERC required PJM to revise several tariff elements in April 2026, meaning the full mechanism is not yet in place. If PJM's revised filing shows they are trying to preserve socialized cost allocation for smaller loads, that signals a fight. Third, track whether any data centre projects announce location decisions citing the April 16 order. If deals start closing in SPP or Texas immediately after the June rule is issued, FERC's intent was clear and the incentives worked. If announcements stay quiet, it means developers are waiting to see if the rule survives its first legal challenge.