Proposed large load cost allocation mechanisms projected to lower transmission costs for existing customers and support continued grid investment

PEWAUKEE, Wis. - Today, ATC posted its projected 2027 transmission revenue requirement, which reflects a network rate decrease of approximately 6% from the 2026 rate if the Federal Energy Regulatory Commission approves pending filings related to serving large new electric loads. If approved, ATC expects to bill $136 million related to large-load data center projects in 2026.

ATC's proposal would have large electricity users pay transmission charges based on how much capacity they request and the service they receive. It also would help protect other customers from paying those costs if the expected new electricity demand does not materialize. Without the large-load cost assignment mechanisms, the network rate would be 16% higher than it would otherwise be in 2027.

"Growing electricity demand presents another opportunity to deliver sustained value to our customers and communities," said Teresa Mogensen, ATC chair, president and chief executive officer. "By aligning transmission charges with the capacity and transmission service required to meet that demand, we can support economic growth, help keep downward pressure on transmission costs and continue investing responsibly in a safe, reliable and resilient grid."

ATC's pending filings include two complementary mechanisms designed to address different phases of large-load development.

First, during construction, the Construction Work in Progress, or CWIP charge, which consists of the financing costs and associated taxes for transmission facilities needed to serve qualifying large-load projects, would ultimately be assigned to the large customer.

Second, after facilities are placed into service, a Minimum Transmission Charge, or MTC, would ensure that the new large load customers pay 100% of the costs incurred to build facilities needed to serve them. The MTC would apply only when regular payments for network service do not reflect the full capacity requested.

ATC's proposal also recognizes that serving a large new electric load depends both on facilities constructed for that load and utilization of the broader transmission network. ATC's federally regulated rates cover the costs of both new and existing transmission facilities, and ATC's local distribution company customers are charged based on their use of the transmission system. More customers sharing the cost of the broader transmission grid means lower costs for existing customers.

The proposed mechanisms apply to qualifying projects involving a new or expanded load of at least 100 megawatts or requiring $100 million or more in transmission facilities. They are designed to address cost-shifting risks during construction and after facilities enter service, including if a project is canceled or substantially modified or if the anticipated load does not fully materialize.

In addition, ATC's 2027 network transmission rate is also lowered by over $100 million of costs that will be shared across the Midcontinent Independent System Operator (MISO) region for Multi-Value Projects that ATC builds and owns, such as the Grid Forward Project.

ATC believes these mechanisms support the fair allocation of transmission costs while helping maintain a safe, reliable and resilient electric grid capable of serving both existing customers and future growth.

ATC is a Wisconsin-based company that moves energy along the regional electric grid in parts of Wisconsin, Michigan, Minnesota and Illinois, serving more than 5 million electric consumers. We are experts at what we do: planning, maintaining, operating and protecting the grid. As the electric industry moves toward renewable generation sources, we are transforming our system to continue delivering energy reliably and safely. We proudly support STEM education programs that empower youth with the skills needed to succeed in tomorrow's energy workforce. For more information, visit www.atcllc.com