SOO Green HVDC Link, a groundbreaking underground transmission project aimed at bringing renewable energy from Iowa to Illinois, on September 24, 2025, secured its final municipal franchise agreement within the state, clearing the $3.2 billion project to proceed towards construction. Bellevue was the 24th and final municipality on the route to sign off on the project, representing a critical breakthrough for the 350-mile high-voltage direct current (HVDC) line.
The project, created through partnership among the United States’ energyRe and Denmark’s Copenhagen Infrastructure Partners, will stretch from Mason City, Iowa, to Yorkville, Illinois. Converter stations at each end will allow the line to send power in both directions. The project aims to move a mix of wind and solar energy, balanced with storage, from the Midwest to population centers in the east. By using existing rail corridors as conduits for an underground transmission line, SOO Green preserves communities and landscapes while addressing one of the most significant challenges in the U.S. power market: reliably transporting low-cost renewable energy to where it is needed most.
Consumers’ benefits
When operating at full capacity, SOO Green will supply 2,100 megawatts of electricity—enough to illuminate almost 1.5 million homes. Developers estimate the project will create thousands of union construction jobs, add $3.2 billion to the local economy during construction. And enhance two large power markets’ grid reliability: the Midcontinent Independent System Operator (MISO) and PJM Interconnection.
Economic studies also pinpoint consumers’ benefits. Research projects the line would save $5.8 billion net over its initial five years in operation, or average monthly residential electricity bill savings of $5.67 for Illinois Commonwealth Edison customers.
“SOO Green represents a bold new model for building the energy grid of the future,” said David Pacyna, CEO of SOO Green. “By going underground along existing rail infrastructure, we’re dramatically reducing disruption to communities and landscapes while creating a vital energy superhighway that strengthens grid reliability and resiliency, optimizes transmission efficiency, and lowers long-term energy costs.”
Attention now turns to Illinois
With approvals in place in Iowa, attention now turns to Illinois, where state legislators are being urged by project officials to pass bills making possible SOO Green’s ability to compete well in the market. Pacyna was hopeful that legislators would recognize the value of the project to help lower costs and improve Illinois’ energy competitiveness in an era of rising electricity prices. Developers also believe this project will support Illinois’ push toward clean energy.
Groundbreaking
If all of the remaining policy and regulatory steps fall into place, project work can begin as early as 2027. With commercial activities in 2031. The project has backing from a consortium of prominent energy and infrastructure companies like Siemens Energy, Jingoli Power, Prysmian Group, and PPL Corporation.
Additionally, for the developers of SOO Green, the final municipal permit in Iowa is no formality—it demonstrates that local communities support the project and its effort to rethink transmission and how renewable energy moves across geography.
Like the multi-state PowerOn Midwest transmission project, SOO Green strengthens the regional grid and supports rising electricity demand. These large-scale transmission lines efficiently move power from where it is generated to where it is needed, helping ensure reliable electricity for homes, businesses, and industries as the energy system adapts to new technologies and growing consumption.
Additionally, the SOO Green HVDC Link aligns with a broader push to modernize and harden the U.S. grid through advanced transmission infrastructure. A similar approach is being taken on the West Coast with the $2 billion Bay Area transmission projects, which recently broke ground to strengthen regional grid reliability. While SOO Green is fully underground, the Bay Area initiative combines both underground and partially underground segments, reflecting a growing preference for buried or hybrid transmission corridors in densely populated or environmentally sensitive areas. Together, these projects highlight a shift toward more resilient, lower-visibility transmission systems aimed at improving capacity, reliability, and long-distance power transfer.
SOO Green Transmission Project – Fact Sheet
Project Overview
Type: High Voltage Direct Current (HVDC) underground transmission line
Length: 350 miles
Route: Mason City, Iowa → Yorkville, Illinois
Corridor: Existing railroad rights-of-way
Capacity: 2,100 megawatts (MW)
Equivalent Power: Enough to supply 1.5 million homes
Markets Connected: Midcontinent Independent System Operator (MISO) and PJM Interconnection
Latest Development
All 24 Iowa municipalities along the route have approved franchise agreements.
Bellevue, Iowa, was the final approval needed, clearing the project for construction in the state.
Economic Impact
Estimated $3.2 billion boost to the regional economy during construction
Support for thousands of union jobs
Projected consumer savings:
$5.8 billion in net savings during the first five years of operation
$5.67 average monthly bill reduction for ComEd customers
Timeline
Construction start: As early as 2027
Commercial operation: Targeted for 2031
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