The ComEd supply rate is the price of the energy itself, measured in kilowatt hours and quoted in cents per kWh. It is the number a supplier puts in front of you, and it is the one part of the bill you are allowed to shop. Understanding where it comes from, and where it stops mattering, is most of what a commercial account needs to know about it.
Where ComEd's default supply rate comes from
ComEd itself does not profit on the energy. If you never sign with a third party supplier, ComEd buys the energy on your behalf and passes the cost through at a default rate, often called the price to compare. That rate is set through state supervised procurement and it updates on a schedule, so ComEd's default is not a fixed number you can memorize. It is a moving reference point.
That moving part matters, because the honest comparison for any offer is against ComEd's current default, not against last year's. A rate that looked good against an old price to compare can look very different once the default resets.
How third party offers compare
Illinois opened the supply half of the bill to competition, so third party suppliers can sell you the energy and compete on the rate. A lower cents per kWh number is a real saving on the supply line. The things worth reading before you sign are the ones that are not the headline rate: whether the rate is fixed or variable, how long it is locked, and what happens when the term ends.
None of that changes the delivery side of the bill. A supplier can only touch supply.
Why supply is often not the number that matters
For a residential account, supply is most of the bill, so shopping it can move the total. For many commercial accounts, it is the smaller half. The demand charge on the delivery side, set by a single thirty minute interval, can rival or exceed the entire supply cost for the month, and no supplier switch touches it.
This is the mechanism behind a common experience: a business switches suppliers and the bill barely moves. The switch did exactly what a switch can do. It changed the price on the half you can shop. It could not change the half that was actually running the bill.
See which half is driving your bill
The only way to know whether supply or delivery is the larger problem on your account is to look at both halves against your own interval data. You can do that on your own ComEd bill, and see the exact interval that set your demand charge, with the free demand charge tool. We do not sell energy and we take no commission. The tool exists to make the bill legible, nothing more.