Data centers in Illinois

The Illinois General Assembly passed the Clean and Reliable Grid Affordability Act on October 30, 2025, and Governor JB Pritzker signed it into law on January 8, 2026, with most provisions effective June 1, 2026. The Illinois Power Agency projects it will save Illinois energy customers 13.4 billion dollars over the next two decades through clean energy procurement and grid reforms. The law does not include specific data center rules; a separate proposal aimed at data centers, the POWER Act, did not pass in the spring 2026 session, leaving data center specific cost protections to ICC dockets and local ordinances instead.

MISO capacity auction prices have climbed sharply, and Ameren Illinois' summer supply price rose to about 11.326 cents per kilowatt hour effective June 1, 2026, up roughly 39 percent from about 8.14 cents per kilowatt hour in summer 2024. Citizens Utility Board estimates that means Ameren customers pay almost 16 dollars more for every 500 kilowatt hours used compared with summer 2024. Capacity costs, which MISO forecasts from expected future demand, make up roughly a fifth of the supply price, and both MISO and CUB point to new and proposed data centers as a major driver of that forecast.

PJM, the regional grid operator for ComEd's territory, saw its capacity auction price jump from 28.92 dollars per megawatt day to 269.92 dollars per megawatt day, a roughly 830 percent increase, largely because of surging data center demand across the PJM footprint. That flowed into ComEd's supply price starting June 1, 2025, adding an estimated 10.50 dollars a month to an average residential bill. The next PJM auction came in at 329.17 dollars per megawatt day, about 22 percent higher again, which is expected to push ComEd supply prices up further starting June 2026.

Ameren Illinois asked the Illinois Commerce Commission for a 129 million dollar increase in natural gas delivery rates. On November 19, 2025 the ICC approved 73 million dollars instead, a 43 percent cut from the request. That works out to roughly a 3.65 dollar a month increase on a typical residential gas bill, well below the 8 to 10 dollar increase Ameren originally sought.

Ameren Illinois asked to recover 59.6 million dollars in its annual reconciliation case, which trues up prior grid spending. The Illinois Commerce Commission approved 48.4 million dollars on December 18, 2025, after consumer advocates identified wasteful spending including a bid to shift 10.7 million dollars in shareholder retirement costs onto customers, which regulators rejected. Citizens Utility Board said the approved amount should leave typical residential rates close to unchanged.

Under an Illinois law that lets ComEd true up its grid plan spending every year, the utility asked to recover 268.5 million dollars in a reconciliation case. The Illinois Commerce Commission approved 243.1 million dollars on December 18, 2025, cutting about 25.4 million dollars including costs tied to a mismanaged customer billing system rollout. Citizens Utility Board estimated the approved amount adds about 3.10 dollars a month to a typical residential bill starting in 2026.

The Illinois Commerce Commission approved ComEd's refiled four year plan for grid upgrades and reliability spending through 2027, worth a 606 million dollar rate increase over that period, about 11 percent less than ComEd requested. Regulators cut roughly 25 percent from the utility's proposed 2 billion dollars in spending. ComEd separately filed its next four year grid plan in January 2026, which is expected to address the newer surge of data center connection requests.

ComEd told regulators it has 75 pending customer applications, mostly data centers, whose combined power demand is bigger than ComEd's entire all time record peak. On March 20, 2026 the Illinois Commerce Commission approved new ComEd tariff rules requiring large data center customers over 50 megawatts to post security deposits, starting at 1 million dollars, so ComEd can recover costs if a project is cancelled or never fully used. The ICC also ordered a separate investigation, due to start by April 23, 2026, into how to keep the cost of new substations and power lines built for data centers from being shifted onto regular households.