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Transmission Load Interconnections

We assist in the development of large load interconnections to the transmission system in our service territory.

We can support load projects that are Eversource retail customers or ISO New England Regional Network Service (RNS) and Local Network Service (LNS) customers. Transmission load interconnections may be subject to either ISO New England tariff or an Eversource state tariff.


  • Data center
  • Large manufacturing or processing facilities
  • Large electric vehicle (EV) charging stations
  • Large load increases due to reduction in carbon footprint or electrification

Services we can provide include the following and often result in a transmission service agreement:

  • Preliminary engineering screening review
  • Cost estimates
  • Potential alternatives
  • General guidance and support

How to Get Started

Initiate a project

Inquiries and project initiation requests can be sent to our Transmission Interconnections and Services Team (TIS) at Provide us with any available data related to the project including proposed size, location, Commercial Operation Date (COD) and site plan.

We will review the materials provided and set up an exploratory and project initiation call as needed.

We perform a transmission study

The preliminary transmission study we perform will identify the initial scope and cost of the infrastructure required to serve the proposed load project. Infrastructure requirements may include the facilities necessary to physically interconnect the project to the existing system, as well as resolving any system overloads resulting from the proposed project.

This is a study funded by the requesting party. The goal of this study is to provide a timely feasibility assessment and order of magnitude cost estimate.

Study steps:

Review project data – We will review the project data provided by the requesting party and develop a scope and fee for the study. Any missing or required information will be requested as needed after review.

Create and finalize study agreement – We will draft a two-party study agreement that will include the scope and estimated cost to perform the study. The agreement will be reviewed and finalized by both parties. Once finalized and the requesting party provides payment, we will commence study work as agreed.

Perform study – The scope of the study depends on project specifics. However, the study will include steady state analysis to demonstrate the impact of the project on the transmission system in New England under N-1 and N-1-1 scenarios. We will develop scope of work for the interconnection and network upgrades required for the project at a preliminary level and provide corresponding non-binding good faith cost estimates. We will draft a final study report which will be delivered to the requesting party.

Review results – The requesting party will review their project report and provide comments and questions. Typically, a results discussion meeting is held between parties.

We can provide assistance with study results

  • Siting and permitting: We will provide assistance with siting and real estate strategy for the transmission facilities required, as well as explain expected required permitting.
  • Rates: We will provide guidance on concerns or questions on applicable transmission rates for the project and any needed potential special contract filings.

After the study

The requesting party can move forward to formal execution outlined below after our transmission study is completed.

This includes steps and agreements to complete the project, subject to changes to meet specific needs. The three phases below allow the project to commit to discrete steps for added flexibility, if desired.

Engineering and design agreement

We will perform an ISO-NE grade System Impact Study (SIS) suitable for obtaining ISO-NE I.3.9 Proposed Plan Application approval, which is necessary for any modification to the existing transmission system. The scope for the SIS study will be reviewed and confirmed by ISO-NE prior to us commencing.

Additionally, the SIS report will be reviewed and approved by ISO-NE. Upon completion we will coordinate with ISO-NE to file required Transmission Proposed Plan Applications in accordance with ISO-NE Planning Procedure 5-1 (PP5-1: Procedure for Review of Governance Participants Proposed Plans), proceed through the regional stakeholder process, and obtain ISO-NE approval.

Upon completion of this study, any additional network upgrades will be identified and cost estimates adjusted.

Amend engineering and design agreement (full engineering and construction)

We will complete engineering and prepare for construction. We will then coordinate with all required internal parties to engineer, procure, construct, site and permit, and operate the new project's transmission facilities.

Operation agreement

The agreement will include the terms and conditions on operating the facility taking transmission service, including but not limited to, operation and maintenance as well as applicable taxes and fees.