Data Center Site Selection in Illinois: ComEd, Ameren, PJM vs. MISO and the Incentive Pause

Illinois’ data center market is centered on the Chicago suburbs. The draw has been dense fiber, a large enterprise and financial customer base, flat industrial land and, until 2026, a state tax incentive program. Supply is tight. CBRE reported Chicago vacancy of 1.9% in the second half of 2025, with no contiguous block of 5 MW or more available, and 2.2% in the first quarter of 2026, when Chicago posted the largest rent increase of the major U.S. markets at 14.7%.¹¹³

Elk Grove Village, just west of O’Hare, calls itself the data center capital of the Midwest; its mayor has said about 20 data centers operate there with five more under construction.¹¹ CBRE’s notable activity included Prime Data Centers fully leasing its Elk Grove Village campus, Equinix announcing a hyperscale campus in Minooka and PowerHouse Data Centers partnering with Hillwood on a 1.8 GW campus in Joliet.¹ Newer development is pushing past the inner suburbs toward sites that can take 500 MW or more, which in practice means the outer ring and beyond.¹

For a site search, the key fact about Illinois is that it is split between two grid operators. The northern part of the state, including Chicago, is served by ComEd and sits in PJM; most of central and southern Illinois is served by Ameren Illinois and sits in MISO.⁴ Confirm the utility service territory of every parcel first, because tariffs, capacity prices and queue times differ on each side of that line.

In March 2026 the Illinois Commerce Commission (ICC) approved a ComEd proposal that lets the utility require deposits from large-load developers, sized to each project’s energy needs. The deposits let ComEd recover costs if a customer goes out of business, moves, or leaves facilities built to serve it under-used.² The commission called the approval an important first step, set aside broader consumer protections as outside the scope of the case, and directed staff to open new proceedings on them.²

Not all of that pipeline will be built, but the queue drives timing for everyone in it. CBRE reported that projects served by ComEd face power delivery delays until 2032 or later.¹ The Illinois Power Agency’s December 2025 resource adequacy study adds a supply problem on top of the delivery problem: it projects shortfalls in ComEd’s northern Illinois territory by about 2029, driven by load growth from data centers, transportation and industry while coal, gas and oil units retire across both regional grids.⁸⁴

Because ComEd is a PJM utility, capacity costs are set in part by PJM’s regional auction rather than by the state alone. Compare an Illinois site with an Ohio or Indiana site on the same basis, and see our PJM regional guide and PJM capacity prices guide for how the capacity market feeds into bills.

Ameren Illinois serves most of downstate Illinois and is in MISO’s Zone 4.⁴⁷ On its first-quarter 2026 earnings call, Ameren reported 850 MW of signed construction agreements in Illinois and said additional projects are under engineering study.¹⁴ State planners have noticed the shift: the Illinois Power Agency’s July 2026 planning materials say updated data center forecasts are higher in the Ameren zone and lower in the ComEd zone, and that the distribution of data center load has moved toward the MISO footprint.³

MISO capacity prices are seasonal and have been volatile. The Citizens Utility Board reported that the Zone 4 summer price fell from a record $666.50/MW-day in 2025 to $424.30/MW-day for summer 2026, still elevated, and named rising forecast load from new and proposed data centers as one of the drivers.⁷ The resource adequacy study projects shortfalls in the Ameren area by about 2031, a few years after ComEd.⁸⁴

MISO’s market rules, queue and resource adequacy constructs are covered in our MISO regional guide; neighboring MISO states include Wisconsin and Missouri.

Illinois’ incentive is the Data Center Investment Program, run by the Department of Commerce and Economic Opportunity (DCEO). A memorandum of understanding sets the terms under which a qualifying data center may receive state and local sales and use tax exemptions for up to 20 years, issued as renewable five-year certificates, and in some cases tax credits.⁵

On June 5, 2026, Governor Pritzker directed DCEO to stop taking new applications as of July 1, 2026, after the General Assembly did not act.⁵⁶ The pause is administrative, not statutory, and how existing agreements are treated is a question for DCEO and counsel.⁶ For a project still in planning, model the Illinois case without the exemption and treat any restart as upside. Our sales tax exemptions by state and incentives vs. power cost guides put that in context.

The Climate and Equitable Jobs Act of 2021 (CEJA) targets a zero-emission power sector by 2045, with earlier phase-out dates for private fossil units located within three miles of an environmental justice community.⁹ That matters for behind-the-meter gas generation, a common workaround for slow grid service elsewhere. The developer of the proposed Lincoln Land Energy Center, a gas plant meant to power a data center campus in Christian County, argued that unless the law changes the plant would have too short a life to attract investors, and the data center developer later abandoned its plans there.¹⁰

In January 2026 the governor signed the Clean and Reliable Grid Affordability Act (CRGA), which sets a target of 3 GW of battery storage procurement by 2030 and lifts Illinois’ ban on new large-scale nuclear plants.¹⁵ CRGA does not add a data center tariff, but storage and nuclear options change the long-run supply picture.

The next fight is the POWER Act, introduced February 11, 2026, which would require data centers to pay for their own energy, invest in renewable generation, report water use and work with host communities.¹⁶ It did not advance before the end of the spring 2026 session, though negotiations may continue; a separate bill, SB 2181, would require energy and water reporting.⁶ Plan for some form of “bring your own clean capacity” rule, and price it before you option land.

Zoning is local in Illinois, and local positions now vary widely. Elk Grove Village markets itself as the Midwest’s data center capital and keeps adding campuses.¹¹ Downstate, Bloomington council members signaled support for a six-month moratorium in May 2026, citing water and energy.¹² Expect hearings to focus on noise, water source, generator emissions and tax revenue.

Water is less of a hard constraint in northern Illinois than in the desert Southwest, but it is a political issue, particularly in areas that draw on aquifers. Reporting bills such as SB 2181 signal where state policy is heading.⁶ Ask the municipal water utility for a written capacity letter and discuss closed-loop cooling early; our municipal water and sewer capacity guide covers what to request.

1. 01Confirm the utility (ComEd, Ameren Illinois, a cooperative or a municipal system) and therefore PJM or MISO.⁴
2. 02Ask the utility where the load would sit in its queue, what deposit or security applies, and what delivery date it will commit to in writing.²
3. 03Model energy and capacity costs for the right market, including the projected shortfall years.⁸⁷
4. 04Run the tax case without the Data Center Investment Program and confirm status with DCEO.⁵
5. 05If on-site gas is part of the plan, test its economics against the 2045 zero-emission target and any environmental justice proximity rules.⁹
6. 06Check for local moratoriums, pending zoning text amendments and the water source before signing an option.

Our large-load tariffs guide explains the agreements you will negotiate, and the screening approach is laid out in our methodology. If you want a second opinion on a specific parcel, get a site reviewed.