ComEd Announces Energization of Expanded Wilton Center 765 kV Substation, Unlocking Illinois’ Largest Cluster of Wind and Solar Projects
ComEd announced today that it has officially energized a major expansion of its 765-kilovolt (kV) Wilton Center substation in southern Will County, marking a significant milestone for renewable energy integration in Illinois. This substantial infrastructure upgrade is designed to support the interconnection of the state’s most extensive cluster of utility-scale onshore wind and solar farms, which are set to begin delivering power to the ComEd grid and the PJM regional energy market starting in 2026.
The expansion represents a cornerstone project in ComEd’s long-term transmission strategy, supporting the growing volume of renewable energy development across northern Illinois. As state and national policies push for greater clean energy adoption, ComEd’s investment in high-voltage transmission infrastructure is critical for enabling the next generation of large-scale renewable resources.
ComEd President and CEO Gil Quiniones highlighted the importance of the accomplishment, stating, “The livening of the Wilton Center expansion project marks a major milestone. The expansion will enable ComEd to deliver more than 2,000 megawatts of new renewable generation through our transmission system to meet growing demands for electricity among residential and business customers. What’s more, interconnecting large volumes of renewable energy in the PJM zone helps us put downward pressure on rising energy costs.”
The scale of the Wilton Center project reflects the enormity of the renewable energy wave coming into Illinois. The expansion increased the substation’s physical footprint by 50%, bringing it to a total size of approximately 1.5 million square feet. Such a large buildout required extensive earthwork and planning, but ComEd and its contractors implemented measures to significantly reduce environmental impact. The project team reused roughly 80,000 tons of topsoil and 90,000 tons of on-site clay to meet grading and foundational requirements. By eliminating the need to haul soil to or from the site, ComEd prevented a substantial amount of truck traffic, fuel use, and emissions—demonstrating how major grid projects can incorporate sustainable construction practices.
The new infrastructure installed at the site includes high-voltage circuit breakers, advanced current and voltage transformers for system instrumentation, surge arresters, enhanced protection and control systems, and upgraded disconnect switches. The addition of this equipment modernizes one of the most important assets in ComEd’s transmission network. To support water management on the expanded site, crews also constructed a new detention pond capable of capturing 2.8 million gallons of stormwater.
Wilton Center has long played a crucial role in ComEd’s grid operations. Originally constructed in 1968 near Joliet, Illinois, the substation is one of the few in the United States that supports 765 kV transmission lines, the highest voltage level in the nation. These ultra-high-voltage lines are essential for moving massive amounts of electricity efficiently across long distances. In fact, less than 1% of existing U.S. transmission lines operate at this voltage, underscoring Wilton Center’s uniqueness and strategic value.
ComEd’s expansion will not only modernize one of its most important facilities but will also allow for the integration of a substantial amount of new renewable energy. Following an additional minor system upgrade planned for the second quarter of 2026, ComEd’s transmission network will have the capability to support the output of up to 2,450 megawatts (MW) of renewable generation from seven large-scale wind and solar installations. These projects will serve both ComEd customers and the broader PJM Interconnection region, which spans all or parts of 13 states plus the District of Columbia.
The renewable projects slated to interconnect through the upgraded substation include:
• Heritage Prairie Wind and Solar Project
Located across western Kankakee County and northeastern Livingston County, this major development—led by Pattern Energy and Repsol—will consist of up to 850 MW of wind capacity, making it the largest onshore wind interconnection in northern Illinois and the largest onshore wind project in the entire PJM territory. The project also includes a 300 MW solar expansion, positioning it as one of the most significant hybrid renewable projects in the region.
• Panther Grove Wind Farms
Panther Grove Wind Energy is developing two separate 400 MW wind facilities, one in Livingston County and the other in Woodford County. Together, these two projects will add 800 MW of clean generation to the grid once fully interconnected.
• Lower Crossing Wind Farm
Located in Kankakee County and owned by Cordelio Power, this project will contribute 200 MW of wind energy to ComEd’s transmission network.
• Osagrove Flats Wind and Solar Project
Situated in LaSalle County and led by Avangrid, Inc., Osagrove Flats is a 150 MW wind project with a planned 150 MW solar expansion. Avangrid is already active in Illinois, with the 100 MW Midland Windfarm in Henry County recently achieving interconnection with ComEd’s system in November.
These renewable energy projects represent a significant step forward for Illinois’ decarbonization goals and underscore the need for continued transmission investment. Their ability to deliver power reliably depends on robust high-voltage infrastructure—precisely what the Wilton Center expansion provides.
Construction efforts at the site were led by ComEd crews in partnership with Lindblad Construction. Engineering, design, and construction support were provided by Burns & McDonnell, one of the nation’s leading engineering firms specializing in energy infrastructure. Their collaboration ensured the project met technical requirements, regulatory standards, and environmental objectives.
As renewable energy development accelerates across the Midwest, projects like the Wilton Center expansion are becoming increasingly important. Beyond enabling specific wind and solar farms, these investments strengthen the reliability and resilience of the broader transmission grid. They also help moderate energy prices by bringing low-cost renewable power into regional markets—an economic benefit that will be felt by customers throughout Illinois and beyond.
With the energization of the expanded Wilton Center substation, ComEd is signaling its readiness to facilitate the next era of clean energy growth and demonstrating how strategic infrastructure upgrades can enable large-scale renewable integration while supporting environmental stewardship and economic value.
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