The figures come from the utility’s cost projections submitted in a regulatory proceeding before the Illinois Commerce Commission. An expert working for the Citizens Utility Board, the Environmental Law & Policy Center, the Natural Resources Defense Council, Vote Solar and the Union of Concerned Scientists reviewed those estimates.

The projected work includes more than $1.4 billion in new transmission lines, $189 million in upgrades to existing transmission infrastructure and more than $1.5 billion in distribution-system improvements. The companies tied to the projects were not identified in the figures. The customers have either begun operating in Illinois since 2021 or are expected to come online by 2031, and each would require at least 50 megawatts of power—roughly enough for a small city.

That much electricity could be used by a large industrial facility. The Citizens Utility Board believes the projects are data centers, which are expanding nationwide amid growing demand for artificial intelligence computing.

“Everyday electric customers are potentially on the hook for billions in higher bills,” said Sarah Moskowitz, the board’s executive director. She argued that large technology companies should pay the costs of connecting their facilities upfront rather than shifting financial risk to other customers.

ComEd says the advocates’ analysis is incomplete and gives an inaccurate picture of who will pay. The utility points to Transmission Security Agreements with large-load customers, approved by state and federal regulators. A ComEd spokesperson said the agreements require customers to cover transmission costs for the term of the agreements, even if they shut down or use substantially less electricity than expected.

The utility said the distribution-system estimates and the deposits required for that work are still being developed. Some projects are years from operation, and ComEd’s engineering assessments are not finished, the spokesperson said, adding that the current $721 million in commitments could rise. The utility also said it supports assigning costs to the large-load customers that cause them.

ComEd has separately asked the Illinois Commerce Commission for authority to reduce data centers’ electricity service when the grid is under heavy strain, including during extreme heat. Consumer advocates say such steps do not eliminate the risk that the utility could build infrastructure for projects that never materialize, leaving costs to be recovered from other ratepayers.

Nick Wallace, a senior associate attorney at the Environmental Law & Policy Center, said consumer exposure could grow if more data centers join ComEd’s pipeline beyond the 30 projects included in the projections.

The advocacy groups are urging Illinois lawmakers to pass the proposed Protecting Our Water, Energy and Ratepayers Act, known as the POWER Act. The measure would require data centers to pay all of their grid-related costs before connecting, and would also set protections related to pollution and water use.

Debate over data centers has intensified as communities raise concerns about their electricity and water demands, as well as noise. The issue is landing amid frustration over rising household expenses and higher electric bills. The Citizens Utility Board says ComEd’s electricity supply price is about 50% higher than it was two years ago.

Gov. JB Pritzker has expressed support for data center regulation. The issue could come before lawmakers during the veto session in Springfield in mid-November and early December.