PowerHouse Hillwood data center in Joliet, Illinois, has retained its transmission agreement after FERC rejected ComEd’s cancellation notice. The 1.8GW data center carries an estimated $20 billion investment and spans about 795 acres.
PowerHouse Hillwood Holding plans 24 principal data center buildings across four development phases. The decision preserves the transmission security agreement while a separate federal court dispute continues.
The Federal Energy Regulatory Commission rejected Commonwealth Edison’s notice on September 22, 2026. ComEd had sought to cancel its transmission security agreement with PowerHouse Hillwood.
However, FERC did not determine whether the agreement’s disputed credit provisions were properly satisfied. Instead, commissioners allowed the existing federal court case to address those contractual questions.
PowerHouse Hillwood Data Center retains transmission agreement
The dispute centers on credit support required under the transmission security agreement. PowerHouse Hillwood contends that it met the initial requirement through a $1 letter of credit.
ComEd challenged the arrangement and later filed its cancellation notice with FERC. The utility’s action followed wider efforts to assess the certainty of large data center loads.
FERC’s decision therefore leaves the transmission agreement in place for now. However, it does not settle the disagreement between the developer and ComEd.
The U.S. District Court for the Northern District of Illinois is handling the related contract dispute. FERC said the court can address the disputed contractual interpretation.
Meanwhile, FERC commissioners linked the case to broader reforms targeting large electricity loads. The commission issued show-cause orders to regional grid operators in June.
Those orders seek clearer rules for connecting large loads to transmission networks. They also address cost recovery and protections against shifting infrastructure costs onto existing customers.
PowerHouse Hillwood Data Center advances major campus plans
The planned data center campus covers approximately 795 acres around South Rowell Road and Bernhard Road. Joliet approved the project’s conditional annexation and preliminary planned development in March 2026.
PowerHouse Hillwood Holding plans four construction phases for the data center campus. Each phase would contain a six-building cluster. The complete development would therefore contain 24 principal data center buildings. City documents estimate approximately 6.936 million gross square feet at full buildout.
Moreover, each building would provide approximately 144,500 square feet across two stories. The development would also require substantial supporting electrical and stormwater infrastructure. Furthermore, each phase would include an electrical substation covering approximately six acres. A separate 25-acre switching station would serve the wider development.
The switching station would sit west of South Rowell Road. City documents identify ComEd as the eventual owner of that facility. In addition, road improvements would also support the data center construction program. The plans include extending Millsdale Road eastward toward Rowell Road.
The project’s scale makes power infrastructure a central component of its construction strategy. Therefore, its planned 1.8GW capacity places substantial demands on the regional electricity network.
The Joliet development is part of a wider expansion of large-scale data center infrastructure across Illinois. A separate development in Chicago’s Illinois Medical District has also advanced, with its construction team already unveiled. The Illinois Medical District data center construction team highlights the growing scale of data center investment across the state as developers plan new high-capacity facilities.
PowerHouse Hillwood Data Center faces wider large-load scrutiny
FERC’s decision arrives as utilities and regulators reassess agreements serving major data center developments. The commission wants stronger safeguards around infrastructure commitments and customer costs. on the other hand, Commissioner David Rosner said security deposits can improve project viability and transparency. He also stressed that developers should retain project-related risks.
Commissioner David LaCerte separately questioned whether a $1 letter of credit provides meaningful protection. His comments focused on potential infrastructure exposure for ComEd customers. In addition, FERC Chairman Laura Swett and Commissioner Lindsay See supported allowing the federal court proceedings to continue. They also emphasized clearer and more consistent agreements for large electricity loads.
For the Joliet development, the ruling removes ComEd’s immediate cancellation action. Nevertheless, the contractual dispute remains unresolved. The project still requires subsequent development approvals for its individual phases. However, the city’s preliminary approval does not itself represent completion of the planned construction.
Project Fact Sheet
Name: Joliet Technology Center
Type: Data center campus
Location: Joliet, Illinois, United States
Developer: PowerHouse Hillwood Holding LLC
Development area: Approximately 795 acres
Planned electricity capacity: 1.8GW
Estimated investment: $20 billion
Planned construction phases: Four
Planned data center buildings: 24 principal buildings
Buildings per phase: Six
Approximate total buildout: 6.936 million gross square feet
Approximate building size: 144,500 square feet
Building configuration: Two stories
Phase electrical substations: Approximately six acres each
Main switching station: Approximately 25 acres
Planned switching station location: West of South Rowell Road
Planned electricity provider: Commonwealth Edison Company
Cooling infrastructure: Closed-loop cooling
Stormwater infrastructure: Phased with each development stage
Primary site roads: South Rowell Road, South Ridge Road and Bernhard Road
Additional road improvement: Millsdale Road extension
Annexation approval: March 19, 2026
Zoning classification: I-1 Light Industrial
Current regulatory issue: Transmission Security Agreement dispute
Disputed credit support: $1 letter of credit
FERC docket: ER26-3257
FERC decision date: September 22, 2026
Federal court: U.S. District Court for the Northern District of Illinois
Current status: Planned data center development with contractual litigation ongoing
Project Team
Developer: PowerHouse Hillwood Holding LLC
Data center development partner: PowerHouse Data Centers
Development partner: Hillwood
Utility: Commonwealth Edison Company (ComEd)
Parent company: Exelon Corporation
Federal regulator: Federal Energy Regulatory Commission (FERC)
Local government: City of Joliet
Planning authority: Joliet Plan Commission
Transmission agreement: Transmission Security Agreement between ComEd and PowerHouse Hillwood
Federal court: U.S. District Court for the Northern District of Illinois
Electrical infrastructure owner: Commonwealth Edison Company, for the planned switching station
Traffic consultant: Kimley-Horn
Development site: South Rowell Road and Bernhard Road, Joliet, Illinois
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