Data centers want PJM power, and northern Illinois is in the bid

I.How a big load gets in line

When a data center developer wants power at the scale we are talking about, roughly tens to hundreds of megawatts (a megawatt is about enough to run a few hundred homes at once), it does not just call ComEd and flip a switch. It files a request that triggers an interconnection study, the engineering review PJM and the local utility run to figure out what wires, transformers, and substations have to be upgraded so the new load does not overload the system.

Those studies take time, often more than a year, and they can slip. PJM has spent the last few years reworking how it processes its interconnection queue because the backlog grew faster than the staff could clear it. Large new loads add a wrinkle the old process was not built for: a single customer asking for the output of a mid-sized power plant, sometimes on a schedule measured in months, not the years the grid usually takes to build.

II.The honest math on your bill

Your bill has two big pieces that a data center boom can push on. One is the cost of the wires, the poles, substations, and transmission lines that have to be built or upgraded to serve new load, which ComEd recovers from ratepayers over time. The other is capacity, the charge that comes out of PJM's yearly capacity auction (the process where PJM pays power plants to promise they will be available on the worst demand day of the year).

That auction cleared far higher in its most recent round than in years past, on the order of several times the prior price at last public report, and more demand on the system is one reason prices climbed. Whether a specific data center raises your bill depends on who pays for the upgrades it needs. If the developer covers its own interconnection costs, the pressure on you is smaller. If those costs get spread across all customers, it is larger, and that split is exactly what regulators are fighting over now.

III.Who decides, and who does not

Four names matter here, and they do not all answer to the same boss. PJM runs the studies and the markets. FERC, the Federal Energy Regulatory Commission, is the federal agency that approves PJM's rules and rules on disputes about how big loads connect. ComEd owns the local wires and does the physical work. The Illinois Commerce Commission (the state regulator that sets ComEd's rates) decides how much of the cost you ultimately see.

The seam between them is where the hard questions live. A dispute over whether a data center can sit right next to a power plant and draw from it directly, called co-location, has already landed at FERC without a clean answer. Illinois lawmakers have started asking whether large loads should sign special contracts that protect ordinary ratepayers. None of that is settled, and the honest summary is that the rules are being written while the line of customers keeps growing.

IV.Worth watching this month

1. PJM's interconnection queue updates and any new rules on large-load additions, posted on PJM's site, are the clearest early signal of how fast this demand actually connects.

2. The Illinois Commerce Commission's open dockets on ComEd rates and grid planning, where any special treatment of large loads would surface first.

3. FERC's handling of the co-location question, which will shape whether data centers can bypass the grid or must pay into it like everyone else.

4. PJM's next capacity auction results, the single clearest number for whether the supply-and-demand squeeze is easing or getting worse.

5. Any ComEd filing about transmission upgrades tied to new large customers in the Chicago area, which is where the wires cost shows up before your bill does.