For more than two decades, Eversource and United Illuminating have collected a little extra on top of their transmission profits — a reward for voluntarily joining the regional power grid operator, ISO New England. The problem, Connecticut now argues, is that joining isn’t voluntary anymore. The state made it the law in 2025. And you can’t pay someone a bonus to do something they’re already legally required to do.
On June 11, four Connecticut agencies — DEEP, the Office of Consumer Counsel, PURA, and Attorney General William Tong’s office — filed a complaint with the Federal Energy Regulatory Commission asking it to pull the charge. If they win, ratepayers save about $4.5 million a year.
What the “Adder” actually is
Back in 2004, FERC wanted utilities to hand day-to-day control of their transmission lines over to independent regional operators like ISO-NE. To sweeten the deal, it let participating utilities tack an extra 0.50% onto their return on equity — the profit margin baked into transmission rates. That’s the “RTO Participation Adder.” Eversource and UI have collected it ever since, paid for by you, on every bill.
The logic made sense in 2004: it was a carrot to get utilities to do something optional. The carrot is the whole legal basis for the charge.
What changed
In 2025, Connecticut passed Public Act 25-173. The relevant piece is short and blunt: a utility can’t own or control transmission facilities in Connecticut unless it participates in ISO-NE. No other option. Participation went from a choice to a mandate.
A Connecticut House member said the quiet part out loud during the debate — paraphrasing, the point of writing the requirement into law was precisely to give FERC the hook it needs to deny the adder. The state engineered the legal predicate on purpose.
So the state’s argument writes itself: an incentive can’t incentivize behavior that’s already required. As the complaint puts it, you can’t reward a utility “for doing what it is supposed to do.”
This isn’t a novel theory
That’s the part utilities should be nervous about. Connecticut isn’t out on a limb — it’s following a path two other states already cleared.
Ohio did this first. Ohio law mandates RTO participation, FERC stripped the adder, and the Sixth Circuit upheld it in 2025 (Dayton Power & Light). California is next — same basic setup, and the Ninth Circuit affirmed FERC’s removal of the adder in July 2025 (PG&E v. FERC). Connecticut’s brief leans hard on both, and for good reason: the Ohio and California statutes do the same thing Connecticut’s does. Two federal circuits have now blessed the move.
Connecticut is the third state in the country to try this, and the first in New England.
Why the dollars are bigger than they look
The complaint flags something worth sitting with. ISO-NE already has the highest transmission costs of any grid operator in the country — rates more than double the average across other regions. New England spends $5.90 on transmission per megawatt-hour of demand, the highest of any U.S. region. Transmission costs in Connecticut have climbed 77% since 2015 and now make up 15-16% of a typical residential bill.
So the adder isn’t sitting on top of cheap rates. It’s an extra premium layered onto some of the most expensive transmission in America, in a state where roughly 30% of adults reported being unable to pay an energy bill in full at one point in 2024.
And there’s upside beyond the $4.5 million. If other New England states pass copycat laws, Connecticut’s share of savings on regionally shared transmission costs could reach $14.5 million a year. This filing is partly a dare to the rest of the region.
What they’re actually asking FERC to do
Four things: declare the continued adder unjust and unreasonable, order ISO-NE to rewrite its tariff to remove it, set a refund date as of June 11 (the filing date), and refund everything collected after that. Tong’s office is explicit that it wants refunds for ratepayers now, not just a fix going forward.
One procedural note: ISO-NE is named as a respondent only because the charge lives in its tariff. The state more or less expects ISO-NE to ask to be dismissed as a mere billing agent — and says it won’t fight that, as long as ISO-NE commits to actually implementing whatever FERC orders.
The takeaway
This is a clean, well-armored filing. The state wrote a law specifically to remove the “voluntary” foundation the adder stands on, then pointed FERC at two federal appeals courts that already approved the exact same maneuver. The comment deadline is July 1, 2026. Expect Eversource and UI to push back hard — but on the law as it currently stands, they’re swimming upstream.
Bonus profits for following the law were always going to be a tough sell. Connecticut just made them a tougher one.
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