FERC Keeps PJM's 50 MW Large-Load Definition and Registry, and Rejects the Plan to Curtail New Data Centers First

PJM filed six things at FERC on August 13. On October 9, FERC accepted two of them ^[1].

The two that survived are the plumbing: a definition of Large Load at 50 MW and a Large Load Registry, both effective today, October 12 ^[1]. The four that did not are the parts that would have decided who gets cut off: Interim Resource Adequacy Service (IRAS), the requirement that utilities serving new large loads bring new capacity to avoid it, the Bring Your Own New Capacity rules, and the removal of uncovered new loads from the capacity auction’s demand curve starting with the 2029/2030 delivery year ^[1]. The order, 197 FERC ¶ 61,019 in Docket ER26-3515-000, came three days before PJM’s requested effective date ^[1].

As this column noted on September 8, the first thing to watch was whether FERC ruled by October 12. It did. The second was the 50 MW line. That held too.

What FERC kept

The Large Load definition is “end-use customer(s) load that has a cumulative peak load of 50 [MW] or greater at a single electrical site,” with affiliated facilities within a one-mile radius treated as one site ^[1]. FERC rejected every request to move it. FirstEnergy wanted 200 MW or a data-center-only definition; the market monitor said 50 MW leaves out a significant number of data centers; EPSA asked why a 49.9 MW load should escape ^[1]. FERC’s answer was short: “any cutoff criterion would inevitably exclude loads sized just below the threshold, and that alone does not render the definition unjust or unreasonable” ^[1]. It also kept manufacturing in, noting that protesters did not argue other large loads draw less or affect the grid differently ^[1].

The one-mile rule stays as well. Equinix, CyrusOne and the Data Center Coalition argued it could pull a long-running legacy facility into the definition because someone else builds nearby ^[1]. FERC said the rule exists so an owner cannot split a campus into several sub-50 MW buildings and avoid the count ^[1].

The registry puts the reporting duty on the load-serving entity, with the local distributor filling gaps ^[1]. Its contents include the load’s location, in-service date for each increment, peak load and ramp schedule, telemetry, backup generation “including fuel type and permitting limitations,” and contracts between the load and its supplier ^[1]. Access follows PJM’s existing confidentiality rules, which let state commissions see the data but generally not state consumer advocates; FERC declined to widen that ^[1]. PJM must make a compliance filing within 30 days that keeps the Large Load definition and deletes the New Large Load definition and every reference to it ^[1].

Why FERC rejected curtail-first

The center of the order is jurisdiction. FERC wrote: “We find that several provisions of the proposed Tariff appear to place obligations directly on Eligible New Large Loads, which are, for the most part, retail customers; that certain other provisions appear to dictate which retail customers taking retail service will be curtailed; and that the proposed compensation framework appears to establish a retail rate” ^[1].

PJM had said it would only tell distributors how many megawatts to cut and leave the choice of customers to the states ^[1]. FERC read the tariff text instead of the transmittal letter. The tariff said distributors “shall” implement curtailment among Eligible New Large Loads, which names a class of retail customers ^[1]. On money, FERC found the tariff sets up a framework “whereby retail customers will be paid by other retail customers for what PJM describes as a wholesale capacity service,” and that letting a distributor and state regulator pick the payers and the level amounts to “allowing a retail regulator to set a wholesale rate” ^[1].

FERC also found PJM had not shown why utilities serving new large loads should be treated differently from utilities serving the same megawatts of other load growth ^[1]. Historically, the order says, PJM’s capacity market has procured capacity for all network load “regardless of retail customer class or whether the load is new or existing” ^[1].

What it does to cost and timing

The rejection was not only about authority. FERC listed problems PJM would have to fix in any refiling ^[1]:

• Reliability standards. NERC standard EOP-011-4 allows firm load to be shed involuntarily only after an Energy Emergency Alert Level 3. PJM proposed cutting IRAS load at EEA1.
• Paying for capacity not bought. Utilities serving excluded loads would still be charged for capacity PJM did not procure for them. FERC has already found that non-firm service for co-located load should not carry capacity charges.
• Location. New capacity brought to cover a load did not have to be deliverable to the load’s zone.
• Existing contracts and the 1 MW problem. A 49 MW site that adds 1 MW would become a 50 MW New Large Load with obligations on the whole 50 MW.
• Locked accreditation. Fixing a new resource’s capacity value for the life of the arrangement could leave the auction buying too little or too much, with the gap falling on other customers.

FERC pointed to one path. A non-firm transmission service like the Non-Firm Contract Demand service in its co-location proceeding “might be considered as a potential avenue,” though it noted that service is voluntary and IRAS was not ^[1].

The timing cost falls on the capacity auction. PJM asked for an October 12 effective date so it could change demand-curve parameters for the 2029/2030 Base Residual Auction, which it said is set to run in December 2026 ^[1]. With the exclusion rejected, that auction’s demand curve does not carve out new large loads that bring no capacity ^[1].

Where the sides stand

Data center buyers largely got what they asked for. Google and Constellation urged FERC to reject everything except the registry ^[1]. The Data Center Coalition and Constellation pointed to the tariff’s own curtailment language as proof it targeted retail customers, the argument FERC adopted ^[1]. The intervenor list includes Microsoft, Anthropic, Equinix, CyrusOne and Verrus ^[1].

On the other side, Pennsylvania Gov. Josh Shapiro argued IRAS was a wholesale capacity product within PJM’s authority, and public interest organizations argued new large loads grow faster than supply and are not similarly situated to other customers ^[1]. The market monitor said IRAS was within FERC’s jurisdiction but relied on states to finish it ^[1].

Commissioner David Rosner concurred and went further on order of curtailment, in both directions. “To be clear, in an emergency, data centers not serving critical functions should be shut off before ordinary customers (Hint: homes, hospitals, and schools should never be curtailed before data centers),” he wrote ^[1]. But he objected to cutting IRAS load before paid demand response, and to dropping it from the demand curve: “The result could be a capacity market signaling that PJM has more than enough capacity while the region sheds thousands of megawatts of demand on an involuntary basis” ^[1].

PJM said it is reviewing the order with “an eye toward how we can fulfill FERC’s requirements while recognizing the responsibilities FERC indicated belong to the states,” according to spokesman Jeffrey Shields ^[2].

The registry may matter more in the other PJM docket. Two days before the order, the Department of Energy told FERC in the backstop procurement case, ER26-3380, that “Without up-to-date and project-level identification, PJM cannot reliably reconcile its base forecast with Load Adjustments, avoid omissions and double counting” or attribute growth to the right zone and supplier ^[3]. DOE filed in support of FERC’s September 29 backstop order and its concerns about how PJM would allocate costs ^[3], the question this column covered on September 30.

What I’m watching

First, the backstop refiling. DOE urged PJM to take FERC’s accelerated option and file a revised backstop procurement tariff on or before October 29, 2026 ^[3]. Whether that filing leans on the newly effective registry for its load counts is the first test of the registry’s use.

Second, the states. FERC “strongly encourage[s] states to continue their important work” on which retail customers are curtailed first ^[1]. This column covered Pennsylvania’s tentative order on that question on October 2. PJM’s compliance filing on the definition is due within 30 days of October 9 ^[1]; whether a refiled IRAS comes with it is open.