Why It Matters
A new analysis of New Hampshire’s potential exit from the regional power grid shows that leaving the system would increase electricity costs for state ratepayers by roughly $148 million annually—a 14 percent rate increase. The findings suggest that despite growing interest in energy independence, the economic realities of grid separation would make power more expensive for consumers across the state.
What Happened
A July 15 report commissioned by the New Hampshire Department of Energy examined whether the state could feasibly withdraw from ISO New England, the regional grid operator that coordinates electricity generation and transmission across much of the Northeast. A 2025 law directed the department to study the question, and Boston-based consultant London Economics International conducted the analysis at a cost of $230,000.
The study found that a complete physical disconnection from the regional grid is not feasible. Maine relies on transmission lines running through New Hampshire to connect with the rest of New England, making full separation impractical. The most likely exit scenario, the report concluded, would involve New Hampshire maintaining its physical transmission connections while attempting to operate independently—described in the analysis as an “unprecedented” move.
The report notes that transmission lines in New Hampshire are owned by private entities including Eversource Energy, Unitil Energy Systems, National Grid, New Hampshire Electric Cooperative, and New Hampshire Transmission LLC. These transmission owners, rather than states themselves, hold membership in ISO New England. The state’s Seabrook Station nuclear plant, operated by NextEra Energy, sells electricity beyond New Hampshire’s borders, further complicating any separation scenario.
Rather than pursue withdrawal, the report recommends that New Hampshire seek reforms within the existing ISO structure to address cost concerns.
By the Numbers
$148 million — projected annual cost increase for New Hampshire ratepayers if the state leaves ISO New England
14% — the percentage increase in electricity rates that would result from departure
$230,000 — cost of the London Economics International study
Top ten nationally — ranking of New Hampshire’s current electricity rates among U.S. states
Zoom Out
New Hampshire is not alone in examining regional grid separation. Maine reached similar conclusions in 2008 when it studied leaving ISO New England, finding the economic and operational barriers too substantial. Connecticut conducted an equivalent analysis in 2020 and arrived at the same assessment. The pattern suggests that while energy independence appeals to policymakers in high-cost electricity regions, the interconnected nature of regional grids and private ownership of transmission infrastructure creates significant practical obstacles.
New England electricity costs remain among the highest in the nation, a persistent concern that has driven repeated calls for grid reform across multiple states. The region’s reliance on natural gas infrastructure, aging generation assets, and transmission congestion all contribute to elevated rates that affect residential and commercial consumers.
What’s Next
The report’s recommendation to pursue reforms within ISO New England rather than attempt withdrawal will likely shape the legislature’s next moves. Policymakers may focus on advocating for changes to regional pricing mechanisms, grid management rules, or transmission investment policies rather than pursuing the costly and operationally complex path of grid separation. The findings provide a data-backed rationale for that approach, though debates over electricity costs and grid governance in New Hampshire will almost certainly continue.