FERC Rejects ComEd Cancellation of $20B Joliet Data Center TSA, Spotlighting Large-Load Interconnection Reforms

The Federal Energy Regulatory Commission on Sept. 22, 2026, declined Commonwealth Edison’s (ComEd) notice of cancellation for a transmission security agreement (TSA) tied to PowerHouse Hillwood Holding’s planned 1.8-GW, $20-billion data center in Joliet, Illinois. The dispute centers on credit support, with PowerHouse arguing a $1 posting satisfied initial requirements, while ComEd sought to terminate amid a pending federal court case in the Northern District of Illinois.

FERC declined primary jurisdiction, leaving contract interpretation to the courts, but commissioners emphasized broader implications. Chairman Laura Swett and Commissioner Lindsay See highlighted the need for clear cost allocation and ratepayer protections in large-load interconnections. Commissioner David Rosner stressed that security deposits ensure project viability and keep risks with developers. Commissioner David LaCerte criticized the nominal $1 letter of credit as insufficient collateral for ratepayer exposure.

This decision aligns with FERC’s June 2026 show-cause orders to RTOs/ISOs, including PJM, directing pro forma cost-recovery agreements by mid-November to address inconsistent terms, cost-shifting risks, and transparency in large-load connections. Related filings show ComEd has secured similar TSAs with other developers like Equinix and QTS, some previously approved under Mobile-Sierra presumptions, while facing objections from the Illinois Attorney General over potential rate impacts. PowerHouse has separately accused ComEd of anticompetitive behavior in related dockets.

The case illustrates systemic pressures from the data center boom—Exelon utilities report an 18-GW pipeline—against grid planning constraints, where inadequate security or ramp schedules could shift upgrade costs to existing customers. Local opposition in Joliet, including lawsuits over land use and resource strain, adds layers of project risk.