Joliet Data Center Power Guarantee Fight Tests Rules
A $587 million utility guarantee dispute over an 800-acre campus could set how much data centers must prepay for grid power.
Updated on Nov. 2, 2026 in Data Centers
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Hillwood, the developer of a planned 800-acre data center campus in Joliet, offered a $1 letter of credit to ComEd in place of the $587 million financial guarantee the utility requires from new data center developments. ComEd scuttled the retail electricity agreement, and Hillwood sued; the case was sent to federal court in Chicago, where a judge denied Hillwood's request to reinstate the agreement. This is a live dispute over a proposed project, not an operating facility.
Why it matters
ComEd began requiring financial guarantees covering power costs from new data center developments in 2025, reflecting utilities' push to shield ratepayers from the cost of supplying very large loads. The dispute tests how far a utility can enforce those guarantees and whether jurisdiction over them sits with federal courts or the Illinois Commerce Commission.
The $587 million guarantee is the amount ComEd requires to cover projected power costs for Hillwood's campus, compared with the $1 letter of credit Hillwood proposed. Six other data-center operators have already signed agreements and posted the full amount, while the question of which regulator has authority remains unresolved.
The players
Hillwood
Real estate developer behind the planned 800-acre, $20 billion data center campus in Joliet, which is in the early stage with the site not yet purchased.
ComEd (Commonwealth Edison)
Northern Illinois electric utility that requires financial guarantees from new data center developers to cover power costs and ended the retail electricity agreement with Hillwood.
The details
ComEd, the Commonwealth Edison utility serving northern Illinois, requires new data center developers to post financial guarantees that cover the cost of the power they will draw, so existing customers are not left paying for capacity built for a single large user. Hillwood, which plans a $20 billion campus on 800 acres in Joliet, offered a letter of credit, a bank-issued promise to pay that can be drawn on if the borrower defaults, in the nominal amount of $1 instead. Hillwood argues the full amount is unnecessary until power is moved to the site in 2029. ComEd then ended the retail electricity agreement, and Hillwood's lawsuit was moved to federal court in Chicago.
Timeline
2025: ComEd began requiring financial guarantees from new data center developments.
2029: Power transfer to Hillwood's Joliet campus is scheduled to begin after completion.
The Tech Race
Six other data-center operators have already signed agreements and posted the full guarantee amount, setting the pattern Hillwood is now departing from. The outcome will indicate whether large AI and cloud campuses in the Chicago region must fund their own grid capacity up front or can negotiate lower security.
Electricity rates for existing Joliet-area customers depend on whether utilities can require large data centers to cover their own power costs up front. Until the jurisdiction question is resolved, the cost-sharing rules for this campus are uncertain.
The takeaway
Watch whether the federal court or the Illinois Commerce Commission takes the case, since that ruling will set who can enforce guarantees on data center power. Residents and ratepayers in Joliet should track any Commerce Commission filing on the Hillwood agreement before the 2029 power transfer.
What happens next
The federal court will decide whether the dispute belongs before the Illinois Commerce Commission, and Hillwood's power transfer is not scheduled until 2029, when the full letter of credit question is expected to resurface.
Further reading
For the wider context on how grid capacity is being rationed for large computing sites, see Data Centers coverage in Joliet.
Source note: This article includes information reported by The Real Deal New York.
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