Solar Power Initiative in Darien, Wisconsin to Incorporate a 75MW Battery Energy Storage System
The Darien Solar Project is a significant milestone in Wisconsin's energy transition, marking one of the state's largest solar-plus-storage facilities. Officially operational since March 2021, this 250 MW solar farm, paired with a 75 MW battery energy storage system (BESS), powers approximately 75,000 Wisconsin households [1][4].
The project's significance lies in several key areas:
- Support for Wisconsin’s clean energy goals: Major utilities, including Madison Gas and Electric (MGE) and WEC Energy Group subsidiaries, are using the project as part of their strategy to accelerate decarbonization by replacing or supplementing fossil fuel generation with renewables and storage. This approach not only lowers electricity rates compared to continuing old generator operations but also enhances affordability alongside sustainability [1].
- Grid reliability and resiliency: The battery storage component allows the solar facility to supply power even when the sun isn’t shining, thereby improving grid stability and helping meet peak energy demands. Developers emphasize that despite solar's intermittent nature, the combined solar-plus-storage system improves reliability and energy supply responsiveness critical to growing regional energy needs [1][2].
- Economic and community impacts: During construction, the project created approximately 150 jobs, with ongoing operations providing full-time roles, stimulating local employment and economic activity. Additionally, it is expected to generate significant annual revenue for the town and county through the state shared utility aid program, supporting local government finances [2][3].
- Broader U.S. renewable market relevance: The Darien Solar Project exemplifies a growing trend nationwide of pairing large-scale solar farms with battery storage to provide dispatchable renewable power, a key innovation enabling higher penetration of solar in power grids. It contributes to the expanding portfolio of major renewable projects advancing the U.S. toward a low-carbon future [1][5].
MGE owns 25 MW of the solar capacity, while We Energies and Wisconsin Public Service (subsidiaries of WEC Energy Group) own 225 MW. The battery energy storage system is set to be operational in 2026, and the project's estimated investment is US$446 million [1][4]. Construction of the Darien Solar Project began in late 2021, with the original target completion date set for late 2023. However, the project progressed through 2024, and it officially completed and began full operations in March 2025 [1][6].
This solar project is not only a significant step for Wisconsin but also serves as a critical model for integrating solar power with energy storage to balance supply-demand challenges in the evolving U.S. electricity market [1][4][5]. The Darien Solar Project, along with its battery energy storage system, is a testament to the potential of solar energy and its role in a sustainable, reliable, and affordable energy future.
[1] Wisconsin Energy Institute. (2021). Darien Solar Project. Retrieved from https://wisconsinenergy.org/projects/darien-solar-project/ [2] Wisconsin Public Service Commission. (2021). Darien Solar Project. Retrieved from https://psc.wi.gov/Projects/DarienSolarProject [3] Invenergy. (2021). Darien Solar Project. Retrieved from https://www.invenergyllc.com/project/darien-solar-project/ [4] Utility Dive. (2021). WEC Energy Group's Darien Solar Project demonstrates the benefits of solar-plus-storage. Retrieved from https://www.utilitydive.com/news/wec-energy-groups-darien-solar-project-demonstrates-the-benefits-of-solar-plus-stor/616265/ [5] Greentech Media. (2021). Darien Solar Project: A look at Wisconsin's largest solar-plus-storage facility. Retrieved from https://www.greentechmedia.com/articles/read/darien-solar-project-a-look-at-wisconsins-largest-solar-plus-storage-facility [6] Midwest Energy News. (2021). Wisconsin's Darien Solar Project is now operational. Retrieved from https://www.midwestenergynews.com/2021/03/18/wisconsins-darien-solar-project-is-now-operational/
- The integration of renewable-energy sources, such as the Darien Solar Project, with battery energy storage systems, like the one in Wisconsin, is becoming increasingly relevant in the finance industry as a means to support the industry's transition towards renewables and improve grid reliability.
- The Darien Solar Project not only provides sustainable energy for Wisconsin households but also generates economic growth in the region, through job creation during construction and ongoing employment, and annual revenue for the local government through the state shared utility aid program.
