Study Examines how Data Centers and Other Large Energy Users May Affect Electricity Prices in Iowa and Wisconsin

­A new white paper prepared by The Brattle Group identifies system conditions, ratemaking approaches, and contractual structures that utilities can leverage to address electricity affordability concerns related to demand growth from large new electricity customers, including data centers and other energy-intensive facilities.

The paper, The Potential Impacts of Large Loads on Electricity Prices: Analysis for Alliant Energy Utilities, examines the evolving relationship between rapid electricity demand load growth, transmission investment, and retail electricity prices across communities served by Alliant Energy in Iowa and Wisconsin.

Commissioned by Alliant Energy, the paper notes that states experiencing the fastest electricity demand growth have historically also seen the largest declines in inflation-adjusted electricity prices, largely because fixed system costs were spread across more energy sales. The question now facing industry decision-makers is whether that outcome can be sustained.

"Sudden load growth from large energy users has become one of the most important and widely debated issues in the electric power industry," said Ryan Hledik, Brattle Principal and coauthor of the paper. "Our analysis shows that affordability outcomes will depend significantly on how utilities structure rates, contracts, and cost allocation mechanisms. When incremental revenues from large customers meet or exceed the costs they impose on the system, existing customers can be protected while communities still benefit from economic development and infrastructure investment."

The paper highlights that Alliant Energy's Interstate Power and Light Company (IPL) and Wisconsin Power and Light Company (WPL) utilities are comparatively well-positioned to manage the risks associated with large-load growth due to existing contractual protections, substantial owned generation resources, and limited exposure to wholesale capacity market volatility.

Among the paper's findings:

• Between 2010 and 2025, electricity price growth in Iowa and Wisconsin remained below or near inflation levels, comparing favorably with national trends.
   
• Historically, nominal increases in Alliant Energy's average retail electricity price have been driven primarily by investments in aging transmission and distribution infrastructure, regional transmission expansion to support reliability, and new generation capacity planned for coal plant replacement.
   
• Alliant Energy's ratemaking framework is designed to ensure that large load customers pay at least the incremental cost of serving them, reducing the risk of cost shifts to existing customers.
   
• Future transmission investments across the Midwest will likely increase regardless of data center growth due to aging infrastructure replacement and regional reliability requirements; the long-term impact of load growth on retail electricity prices will depend in part on whether revenue from load growth outpaces the cost of new infrastructure investment.

The paper also outlines a growing set of utility and regulatory practices emerging across the United States to address affordability concerns tied to rapid load growth. These include minimum billing commitments, take-or-pay provisions, collateral requirements, exit fees, long-term contracts, and direct assignment of customer-specific infrastructure costs.

The paper notes that transmission investment remains an area of uncertainty because regional transmission planning and cost allocation decisions are made by transmission owners and regional grid operators rather than by IPL and WPL themselves. Even so, the analysis concludes that appropriately designed tariffs and contractual protections can significantly mitigate affordability risks for existing customers.

The Potential Impacts of Large Loads on Electricity Prices: Analysis for Alliant Energy Utilities was authored by Long Lam, Ryan Hledik, Sanem Sergici, Adam Bigelow, and Tina Zhang. The full paper and two-page summary are available on Brattle's website here.