ISO New England's New Rules for Big Loads: What Data Centers Must Do to Connect — and What It Means for Massachusetts Buyers
ISO New England, the New England Power Pool, and the region's transmission owners filed a proposal with FERC this week that sets new ground rules for the biggest new electricity customers in New England — data centers and other large loads.
The filing answers FERC's June 18, 2026 show-cause order (Docket EL26-72-000), which asked every regional grid operator how it plans to handle the surge of very large new loads. FERC declined to write one national rule; instead, each grid operator is filing its own. ISO New England's answer is due by November 16, 2026.
Here's what the proposal does:
It defines a "large load." A commercial or industrial customer at a single site with gross peak demand of 50 MW or more, interconnecting to the transmission system at a voltage above 60 kV. Existing loads that meet the definition are generally exempt unless their demand grows by 50 MW or more from their June 18, 2026 baseline.
It creates a formal application and study process. Applications open June 1, 2027. Each application carries a non-refundable $50,000 fee and a $150,000 study deposit, and studies are to be completed in 90 days unless additional electromagnetic transient or cluster-study
analysis is required. ISO New England also plans to post the application queue publicly — each load's size, location, status, and requested service type.
It creates three transmission services for large loads: firm, interim, and non-firm. Under firm service, all required network upgrades must be completed, and the load must designate new capacity under a "bring your own new capacity" requirement. Interim service
lasts up to seven years, or until the required upgrades are in service, whichever is longer. Loads on interim and non-firm service can be re-dispatched — effectively curtailed — when their local price exceeds $250/MWh. The region crosses that threshold in only about 1%
of hours today.
It closes two loopholes. Large loads would be barred from netting their load against behind-the-meter generation, and loads on interim and non-firm service would be excluded from the region's installed capacity requirement — so they can't lean on capacity paid for by
everyone else.
The transmission services themselves would be implemented starting June 1, 2028. Stakeholder discussions on the details of the "bring your own new capacity" requirement continue into 2027. FERC has not yet ruled on the filing — this is a proposal, and it can change.
Why It Matters
This is the other side of the data-center story. The demand is real, and it is arriving fast: data-center power demand has been growing roughly 19% a year since 2000, against grid growth of about 2%, and data centers now account for about 5% of U.S. grid capacity. Every
grid operator in the country is being asked the same question — who pays for the wires, the upgrades, and the new generation these loads need?
ISO New England's answer is blunt: the new load pays. The proposal is designed, in ISO New England's words, to preserve the reliability of the regional bulk power system and avoid shifting costs to consumers. A data center that wants firm service must bring its own new capacity and wait for its upgrades to be built. One that wants to connect sooner can take interim service — but it accepts the risk of being re-dispatched when prices spike.
That is a very different posture from the old model, where a large new customer could interconnect, draw on the existing system, and leave the cost of the upgrades it triggered to be spread across everyone else's bill.
It also matters because FERC is now handling this region by region. PJM filed its own large-load proposal in August. NERC separately petitioned FERC on October 21 to bring data centers of 50 MW or more under mandatory reliability standards, with comments due November 20. The rules that govern how the biggest new loads connect are being written right now, in parallel, across the country — and they will shape power costs for every other customer for a decade.
What It Means for Commercial Buyers
For Massachusetts buyers, the near-term picture is different from the one in PJM — and that difference is worth understanding.
New England's large-load pipeline is small, for now. ISO New England's first large-load forecast found just 285 MW of large-load projects in the region. Compare that with PJM, where data-center load is driving capacity prices from $28.92 to $329.17 per MW-day.
Massachusetts buyers do not face a data-center load wave today. Their bigger risk remains gas deliverability on the coldest winter days — the same constraint behind the $122.58/MMBtu Algonquin Citygate print during Winter Storm Fern and the roughly $6 billion winter of wholesale electricity costs.
But this filing protects you if that changes. The whole point of the proposal is that a large load arriving tomorrow cannot push its costs onto your bill. Firm service requires the load to bring its own capacity; interim service means the load, not you, absorbs the curtailment risk when prices spike. If a data-center wave does reach Massachusetts, the cost-allocation fight is being settled before it arrives, not after.
Watch the June 1, 2027 date. That is when the application and study process opens. It is the first concrete milestone to track: which loads apply, how big they are, and where they want to connect. The public queue will make that visible in a way the old process never
did.
Watch the "bring your own new capacity" details in 2027. The stakeholder work on that requirement is unfinished. How strict it is — and how much new generation a large load must actually bring — will determine whether firm service is a realistic path for data centers or a door that stays mostly closed.
And watch FERC. The filing is a proposal. FERC could accept it, modify it, or send it back. The November 16 filing deadline and the June 2027 start date are the proposal's own timeline, not FERC's decision.
PEM Perspective
The grid is being asked to do something it was never designed for: absorb a new class of customer the size of a small city, on timelines measured in months, without raising costs for everyone already connected. ISO New England's answer — you pay your own way, you bring
your own capacity, and if you want in early you accept being cut back when prices spike — is the right framework. The details still matter, and the "bring your own new capacity" work in 2027 will decide how much of it holds.
For Massachusetts buyers, the message is narrower and more useful: your near-term risk is still winter gas deliverability, not data centers. But the rules that would protect you if large loads arrive are being written now, and they are being written in your favor. That is worth knowing — and worth watching as FERC takes up the filing.
We will keep tracking this docket and the June 2027 application opening, and what they mean for your energy strategy. — Tony Zelinski, Premier Energy Management
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