Greater Portland Transmission Upgrades Projects

Central Maine Power (CMP) is proposing the Greater Portland Transmission Upgrades Project, a multi-year initiative to build a modern network of substations, upgraded infrastructure, and strengthened grid sections stretching from Yarmouth through Greater Portland.

 

These improvements are designed to: 

  • Replace aging equipment.  
  • Expand capacity to meet growing electricity demand.  
  • Enhance the reliability of the electric system for more than 200,000 customers.  

 

Although early in the process, this project aims to support this region’s future energy needs as more heat pumps, electric vehicles, electrified water transportation and renewable energy are utilized by our customers.

 

 

Project Review Process  

Before we can begin detailed design and construction, this project must be reviewed and approved by the Maine Public Utilities Commission (MPUC). We submitted the application for review in September 2025. On July 16, 2026, the MPUC determined the application is complete and initiated a comprehensive and transparent review of the project’s merits, which will take place over the next twelve months.  

Information about the proceeding (Docket Number 2025-00276), including project filings, schedules, and opportunities for public participation, is available on the MPUC website.

 

Public Engagement 

In December 2025, we hosted a series of public workshops that provided residents, business owners, municipal officials, and other stakeholders with an opportunity to learn more about the project, ask questions, and provide feedback. We appreciate everyone who participated and helped inform our ongoing planning efforts. 

We are currently planning additional opportunities for public engagement. More information will be provided when they are scheduled.  

 

Public workshops:

Below are links to information that was provided at the 2025 public workshops: 

 

Contact us 

  • Project Information Line: 1.888.267.0831 
  • Email: outreach@cmpco.com  
  • Please refer to Greater Portland Transmission Upgrades Project in your message. 

Frequently asked questions

Central Maine Power (CMP) is proposing a major upgrade to the electric grid serving Greater Portland and surrounding communities. This initiative will strengthen the grid, improve reliability, and prepare communities for future growth as Maine’s economy and housing needs expand.

The proposed project route runs through areas of Yarmouth, Cumberland, Falmouth, Westbook, and Portland. 

NOTE: No work for the Greater Portland Transmission Upgrades Project has started. Any recent work in these areas has been part of our standard operations and maintenance work, including our Structure Replacement Program. Please see our project website for more information and work locations:  Structure Replacement Program.  

The investments proposed in the Greater Portland Transmission Upgrades Project are designed to: 

  • Support 200,000 CMP customers in and beyond Greater Portland and benefit all Mainers who rely on businesses and services in Southern Maine.  
  • Better protect critical facilities like hospitals, universities, businesses and residences from large-scale outages.  
  • Prepare for the future by adding capacity for new homes, businesses, and clean energy goals and address aging infrastructure near the end of its operational life.  
  • Improve storm resiliency so communities can recover faster from extreme weather.  
  • Help communities meet climate action goals by enabling electrification, renewable energy integration, and reducing reliance on fossil fuels.  
  • Upgrading two substations (Cumberland and East Deering). 
  • Rebuilding transmission lines in Westbrook and between Cumberland and Falmouth. 
  • Installing a new transmission line from Cumberland to Portland mainly using existing rights-of-way. 
  • Building a new substation near Portland’s wastewater facility. 
  • The project was submitted to Maine Public Utilities Commission (MPUC) in September 2025.  
  • If approved the project will take 3–4 years to complete.  
  • The MPUC determined CMP’s application to be complete in July 2026, and the review process could take up to one year.  
  • Reduces outage vulnerability in Southern Maine, the state’s economic hub.  
  • Creates backup connections so power can flow between communities during outages.  
  • Adds grid capacity to relieve energy bottlenecks and support housing, electrification, and renewable energy.  
  • For information about the MPUC review process, visit the MPUC website
  • For project information contact our Project Outreach team:  
    • Project Information Line: 1.888.267.0831  
    • Email: outreach@cmpco.com   
    • Please refer to Greater Portland Transmission Upgrades Project in your message.