VT — Power Infrastructure Updated 2026-07-17

Vermont

ISO-NE Queue Bottlenecks Transmission Constraints

1. Grid operator and market structure

  • Balancing authority / RTO: Vermont is served by ISO New England (ISO-NE), which operates the regional wholesale markets and transmission system for the six New England states. ISO-NE’s long-term load forecast and CELT materials are the key regional planning sources for large-load impacts. ISO New England, 2026-06-10
  • Retail market structure: Vermont retail electric service remains primarily a regulated utility-service model rather than broad retail choice. This matters because large-load tariff or contract protections would generally be handled through utility tariffs, utility contracts, and Vermont PUC oversight rather than retail supplier switching. U.S. EIA Vermont State Profile, 2026-06-10

2. Interconnection queue status and large-load forecast

  • Queue access and scope: ISO-NE’s public interconnection queue covers requests for new or uprated generating facilities, elective transmission upgrades, and transmission service requests; it does not cover every distribution-level load interconnection or retail-customer onsite resource. Therefore, behind-the-meter generation or a distribution-connected data center self-supply arrangement may not appear in the ISO-NE queue. ISO New England Interconnection Request Queue, 2026-06-10
  • Queue reforms: ISO-NE continues implementing FERC Order 2023 reforms through cluster-study procedures. ISO-NE’s 2025 Regional System Plan describes the transition to the Transitional CNRC Group Study and Order No. 2023 Transitional Cluster Study, and VELCO has also posted a point-of-interconnection heat map intended to satisfy FERC Order 2023’s public interconnection-capacity mapping requirement. ISO New England 2025 Regional System Plan, 2025-11-06; VELCO Planning, 2026-06-10
  • New 2026 large-load forecast: ISO-NE added a large-load forecast to the CELT 2026 process, published the final CELT report on May 1, and updated the public forecast data on June 5. Projects included in the forecast must be 20 MW or larger and have entered a formal study agreement; the March 27 final-draft materials show a 200 MW nameplate data-center project in northeastern Massachusetts (NEMA) through 2027 and an 85 MW general-electrification project in Connecticut through 2040, before derating. Neither project is in Vermont. ISO New England CELT report index, 2026-05-01; ISO New England load-forecast index, 2026-06-05; ISO New England, 2026-03-27
  • Regional large-load scale remains limited: ISO-NE’s March 2026 forecast materials stated that prospective large loads in New England remained limited in number and scale, with recent transmission-owner data showing only a couple hundred MW in the formal study phase and no data-center proposal scale comparable to other U.S. regions. ISO-NE’s June 2 Consumer Liaison Group presentation summarized the near-term status as “only a few projects in formal study” totaling less than 300 MW, with about 110-130 MW peak-demand impact in the 2030s-2040s after forecast treatment, and stated that large loads are not yet a major driver of New England load growth. ISO New England, 2026-03-27; ISO New England, 2026-06-02
  • Federal/regional large-load policy context: In a February 6 response to members of the New England Senate delegation, ISO-NE said no new large data centers or other large electrification projects had committed to construction in New England at that time, data centers were not then a driving factor in regional wholesale costs, and ISO-NE was monitoring FERC and regional large-load interconnection reforms. ISO New England, 2026-02-09
  • FERC opened an ISO-NE large-load tariff proceeding: On June 18, FERC preliminarily found that ISO-NE’s tariffs may be unjust and unreasonable because they may not contain adequate rules for large-load interconnection and co-location. The show-cause order in Docket EL26-72-000 covers ISO-NE and participating transmission owners including Green Mountain Power, Vermont Electric Cooperative, Vermont Transco, and VELCO, and directs responses on study procedures, cost allocation and recovery, co-location, flexible transmission service, and operating requirements. This is a pending federal/regional proceeding, not a final Vermont interconnection rule. ISO-NE and the transmission owners announced that they intended to file by August 3 for a 90-day abeyance; if FERC grants it, they plan a stakeholder process followed by tariff changes due November 16. Neither step had occurred by July 17. FERC show-cause order, 2026-06-18; ISO New England Newswire, 2026-06-29

3. Ratepayer protection (large-load tariffs, cost allocation)

  • No Vermont data-center tariff/order is in force. Keyword review of the Vermont PUC’s public case portal did not identify an order or tariff creating a data-center-specific rate class, large-load tariff, or cost-allocation mechanism through July 17, 2026. H.727 would have required PUC-approved “large load service equity contracts” for data centers, but the bill was vetoed and the veto was sustained. The FERC show-cause case is regional and does not itself create a Vermont retail tariff. Vermont PUC ePUC case search, accessed 2026-07-17; Vermont Legislature H.727 status, 2026-05-29; Vermont Legislature H.727 as passed by both House and Senate, 2026-05-22; FERC show-cause order, 2026-06-18
  • What H.727 would have required: The final bill would have required data centers to be served through PUC-approved large-load service equity contracts that prevent ratepayer cost shifting, include excess-demand charges, collateral for stranded-cost risk, curtailment procedures, applicable tax/charge collection, and periodic PUC review at least every two years. These provisions did not take effect. Vermont Legislature H.727 as passed by both House and Senate, 2026-05-22
  • Existing planning safeguards: VELCO’s long-range transmission planning process is updated every three years, looks out 20 years, identifies reliability criteria violations, and evaluates transmission and non-transmission alternatives through the Vermont System Planning Committee process. This is a statewide planning safeguard, not a data-center-specific tariff. VELCO Planning, 2026-06-10; VELCO 2024 Vermont Long-Range Transmission Plan, 2024-09
  • Utility testimony: Green Mountain Power told Senate Natural Resources and Energy on April 22, 2026 that its existing Rate 70 is designed for high-usage/high-demand customers, and that a typical large-load customer under that rate could contribute to fixed costs and lower costs systemwide. This was utility testimony in support of the House-passed H.727 framework, not a PUC-approved data-center tariff. Vermont Legislature / Green Mountain Power testimony, 2026-04-22
  • Existing Rate 70 terms: GMP’s PUC-approved Rate 70 applies to commercial and industrial service taken at 115 kV with demand of at least 10 MW. Its special-contract provision allows GMP to require a PUC-approved contract rate when a customer’s unique requirements would impose significant costs not recovered through standard rates. That provision is a general large-customer safeguard, not a data-center-specific rate class. Green Mountain Power Rate 70 tariff, 2025-10-01
  • Six-state consumer-protection commitment: On July 1, the New England states, including Vermont, committed through NESCOE to coordinate on large-load policy, affordability, reliability, and local-community protection. The statement says FERC’s proceeding addresses transmission-customer cost shifting while protection of retail customers remains a state responsibility; it is a regional policy commitment, not a Vermont tariff or PUC order. New England States Committee on Electricity, 2026-07-01

4. Generation adequacy and resource development

  • In-state capacity context: Vermont’s in-state generating fleet is small relative to potential hyperscale data-center loads, so large new loads would be evaluated in a regional ISO-NE planning and market context as well as through local utility interconnection review. U.S. EIA Vermont State Profile, 2026-06-10
  • Regional planning signal: ISO-NE is now explicitly tracking data centers and other step loads in its forecast process, but its 2026 materials say large loads are not yet a major driver of regional load growth. ISO New England, 2026-06-02
  • Potential cost allocation issue: ISO-NE’s February 2026 congressional response emphasizes that New England’s current demand growth is primarily driven by electrification of heating, transportation, and other sectors, not committed data centers; nevertheless, ISO-NE is monitoring large-load and co-located-load reforms because future data-center growth could affect resource adequacy, transmission planning, and cost allocation. ISO New England, 2026-02-09
  • Resource-adequacy review now required: FERC’s June 18 order separately required ISO-NE to report on the regional resource-adequacy effects of current and forecast large loads, including whether the capacity market is sending adequate signals. ISO-NE identified July 20 as the filing deadline, three days after this update’s cutoff; the order had not decided those questions as of July 17. FERC show-cause order, 2026-06-18; ISO New England Newswire, 2026-06-29

5. Utility load forecasts and data center demand treatment

  • VELCO forecast baseline: VELCO’s 2024 Long-Range Transmission Plan remains focused on electrification, clean-energy adoption, and Vermont-specific reliability needs over a 20-year horizon rather than a quantified Vermont data-center load-growth scenario. VELCO 2024 Vermont Long-Range Transmission Plan, 2024-09
  • 2027 Vermont forecast process still has no explicit data-center scenario: Vermont System Planning Committee materials for the 2027 Long-Range Transmission Plan show medium and high load-forecast scenarios differentiated by electric-vehicle adoption, not by a separate data-center or other large-step-load case. This process is underway and does not supersede the completed 2024 plan, but it indicates that public Vermont planning assumptions had not yet incorporated a quantified data-center scenario. Vermont System Planning Committee forecast assumptions, 2026-03-25
  • GMP large-load site analysis: Green Mountain Power testified that it studied adding 50-200 MW at selected locations - Williston near GlobalFoundries, New Haven near the VELCO substation, Vernon near the former Vermont Yankee site, and West Rutland/Granite - and found that those additions could be made without significant system concern and could lower customer costs. The testimony did not identify a live interconnection request or committed project. Vermont Legislature / Green Mountain Power testimony, 2026-04-22
  • Regional-plan siting assessment is not a load forecast: Chittenden County’s ECOS Regional Plan, adopted May 20, says current transmission-capacity conditions may make southern Vermont more likely than northern Vermont to attract a large data center and directs continued monitoring of electricity, ratepayer, transmission, land, water, and job effects. This is regional planning guidance, not a quantified utility forecast or a determination that transmission service is available at any site. Chittenden County Regional Planning Commission, 2026-05-20
  • No filed or committed large-scale Vermont project in utility forecast materials located: Vermont Public reported in February that the Department of Public Service knew of no current large-scale data-center proposal and GMP described only speculative inquiries. In June, PowerTransitions disclosed a lease at the approximately 140-acre former Vermont Yankee property in Vernon and identified a data center as one of several possible future reuses. The concept was preliminary, likely years from permitting, and had no announced MW load or interconnection request, so it does not yet change the utility forecast. Vermont Public, 2026-02-26; Vermont Public, 2026-06-15

6. Behind-the-meter / co-location / direct supply

  • Queue visibility limits: ISO-NE’s queue is not a complete inventory of distribution-level load interconnections, retail-customer onsite generation, or behind-the-meter resources. Large data-center self-supply arrangements could therefore require utility and state-level checks even if they do not appear as ISO-NE generation queue entries. ISO New England Interconnection Request Queue, 2026-06-10
  • Co-location policy context: ISO-NE’s February 2026 letter identified co-located loads, large-load interconnection, and cost allocation as active federal/regional policy topics. FERC’s June 18 show-cause order converted those questions into a formal ISO-NE tariff proceeding and specifically requested rules for co-located loads and flexible transmission service. The proceeding includes Vermont transmission owners but remained pending at this cutoff; it is not Vermont-specific PUC action. ISO New England, 2026-02-09; FERC show-cause order, 2026-06-18

7. Transmission constraints and planned upgrades

  • VELCO planning process: VELCO’s 2024 plan is the controlling Vermont long-range transmission-planning document identified in this review; it evaluates transmission and non-transmission alternatives for reliability needs over a 20-year horizon. VELCO Planning, 2026-06-10; VELCO 2024 Vermont Long-Range Transmission Plan, 2024-09
  • ISO-NE Vermont needs assessment: ISO-NE’s 2025 Regional System Plan says the Vermont 2033 Needs Assessment found one non-time-sensitive thermal violation under 2032-2033 winter peak load conditions, but ISO-NE paused immediate competitive solution work because the need-by date was late in the ten-year horizon and evolving factors could affect solutions. ISO New England 2025 Regional System Plan, 2025-11-06
  • Siting implication: GMP’s April 2026 testimony suggests large loads above 50 MW would typically need connection to the 115 kV system and that location matters; the selected Vermont locations it studied were near existing large-load or transmission assets. Vermont Legislature / Green Mountain Power testimony, 2026-04-22
  • Vernon site context: PowerTransitions cited the former Vermont Yankee property’s existing high-voltage switchyard as an asset for possible redevelopment, including a preliminary data-center concept. No load, upgrade requirement, study agreement, or interconnection filing was announced, so the lease is a site-control development rather than evidence of available transmission service. Vermont Public, 2026-06-15

Notes / Gaps