Alliant Energy's 100-MW Wisconsin battery goes live, extending solar journey
22 October 2026
Alliant Energy's first 100-megawatt (MW) battery energy storage system is now operational in Grant County, Wisconsin, paired with the utility's 200 MW solar project. The 100 MW / 400 MWh battery, adjacent to the Grant County Solar site in Potosi, represents the latest phase of Alliant Energy's storage expansion in the state.
The Grant County installation forms part of Alliant Energy's larger initiative, launched in 2022, to enhance its renewable energy capacity across Wisconsin. On September 30, 2022, the company submitted plans to the Public Service Commission of Wisconsin (PSCW) for 175 MW of battery storage in Grant and Wood counties, complementing two pre-approved solar arrays.
PSCW Approval Brings Alliant Energy's Wisconsin Battery Expansion to Nine Projects
The PSCW authorized these battery projects on August 9, 2023, enabling construction to proceed. The Grant County unit marks the fourth approval out of nine granted within a two-year period. Alongside the 75 MW / 300 MWh Wood County development, regulators have also approved storage systems ranging from 25MW to 100MW at former coal plant locations and new solar sites in Fond du Lac, Oneida, Dane, Ashland and La Crosse counties, per PSCW records. Wood County's installation, located 75 miles northeast near Saratoga, achieved operational status in December 2023.
Developing the storage facility represented a four-year process involving Alliant, regulators, and community stakeholders. This included legal proceedings that concluded favorably in 2023 when a farm organization's lawsuit was resolved. "This energy storage system represents a strategic component of our plan to deliver cleaner, more dependable power to customers," stated Tyler Huebner, Alliant Energy's chairman and CEO, in the company's May 2024 announcement. "It enhances grid stability, captures surplus solar generation, and ensures consistent electricity delivery to meet increasing demand."
Large-Scale Storage: A Key Part of Alliant's Clean Energy Push
The new battery significantly bolsters Alliant's expanding storage infrastructure, supporting its wider Wisconsin renewable energy program. In a February 2024 regulatory filing, Alliant projected that renewables would constitute 60% of its 23-gigawatt generation portfolio by 2035.
Storage systems will play a pivotal role in this evolution. "We're targeting 325 megawatts of energy storage statewide to complement our portfolio expansion," Huebner informed investors during the February 9, 2024 annual meeting.
While celebrating this milestone, Alliant noted additional projects remain underway. Following the Wood County installation, the company operates two 25-MW storage facilities in Ashland and Dane counties. Future battery deployments will extend beyond state lines, including an 800 MW collaboration with an undisclosed partner announced October 2, 2024.
Grant County Battery Part of 175 MW Wisconsin Storage Push
This battery represents the completion of Alliant Energy's 175-MW Wisconsin storage initiative first outlined in its September 2022 PSCW filing. That submission characterized battery storage and solar generation as "critical components of our Clean Energy Blueprint."
With installation complete, the Grant County facility expands Alliant's growing storage network. A company representative confirmed its strategic placement supports 11 solar developments either operational or planned across Wisconsin.
The battery integrates with 1,100 MW of existing solar capacity statewide, specifically complementing the 100-MW Grant County solar farm that became operational earlier in 2024.
Alliant initially announced this storage project in its June 24, 2024 regulatory filing. At that time, documents indicated the battery would provide four hours of discharge capacity following PSCW's expedited approval process.
Putting It All Together
The 100-MW Grant County battery stands as the current centerpiece of Alliant Energy's Wisconsin clean energy portfolio, though not the final storage installation planned. The company has outlined ambitions for continued large-scale storage expansion.
Officials emphasized customer benefits: combined with the 200-MW solar farm, this storage system can power approximately 100,000 homes for four hours, extending Alliant's renewable energy utilization.
For Alliant Energy, the Grant County project exemplifies their commitment to regional energy solutions, increasingly vital for balancing industrial energy requirements and supporting Wisconsin's clean energy transition.