When a business owner asks what their ComEd rate is, they usually mean the cents per kilowatt hour someone quoted them. That number is real, but it is only one piece of what a commercial account actually pays, and on many bills it is not the piece that matters most.
A ComEd commercial rate is really three different prices doing three different jobs: a supply rate you can shop, a delivery rate you cannot, and a demand charge set by a single thirty minute interval. Each is measured differently, and only one of them is the number on the flyer.
Supply: the rate you were quoted
Supply is the energy itself, measured in kilowatt hours and priced in cents per kWh. This is the half of the ComEd bill that Illinois opened to competition, so a third party supplier can sell it to you and compete on the rate. It is also the number everyone talks about, because it is the one a salesperson can change.
The supply rate moves. ComEd's own default supply rate is reset periodically through a state supervised auction, and third party offers rise and fall around it. That is worth knowing before you sign a fixed rate, because the honest comparison is against ComEd's current price to compare, not against last year's. But supply is only ever part of the story, and for a lot of commercial accounts it is the smaller part.
Delivery: the rate you cannot shop
Delivery is what it costs to move that energy over ComEd's wires to your building. Illinois left this half a regulated monopoly, because it makes no sense to run three sets of wires down the same street. You cannot shop it, and you cannot get off ComEd, no matter who supplies your energy.
The delivery rate is not a single cents per kWh figure. It is a bundle: a fixed customer charge, some energy based distribution charges, and, for commercial accounts, a demand charge that is often the largest single line on the bill.
The demand charge: the rate set by one interval
On ComEd commercial accounts the delivery demand charge appears as the Distribution Facilities Charge. It is a flat rate per kilowatt, applied to the highest thirty minute demand your site recorded inside the on-peak window, nine in the morning to six in the evening on weekdays. Not the energy you used. The single highest rate at which you pulled it.
That per kilowatt rate depends on your delivery class and the year. Reconstructing it from real reconciled ComEd bills:
- A Small Load account (under 100 kW) on a 2025 bill was billed about $14.59 per kW. On one such account, a 40.91 kW peak demand produced a $596.88 Distribution Facilities Charge for the month.
- A Medium Load account (100 to 400 kW) on a 2025 bill was billed about $14.92 per kW. On one such account, a 242.57 kW peak produced a $3,619.14 charge in a single month.
- A 2026 Retail Delivery Service account was billed about $12.93 per kW under the newer bill format. On one such account, a 46.20 kW peak produced a $597.37 charge.
Each of those figures was reconciled to the cent against the bill it came from. The per kilowatt rate is not the point. The point is that one interval, often lasting half an hour, sets a line that can rival or exceed the entire supply cost for the month.
Why the rate you were quoted is not the rate you pay
Put the three together and the reason a quoted rate rarely predicts the bill becomes clear. The quote changes the supply price. The delivery price is fixed by regulation. The demand charge is set by your own load, on the one interval you probably were not watching. Two businesses on the identical supply rate can pay very different totals depending on how peaky their demand is and when that peak lands.
This is also why switching suppliers so often barely moves the bill. The switch touches the one price you can shop, while the delivery charge and the demand charge, the parts you cannot shop, keep doing what they were doing.
See your own numbers
Everything above was reconstructed from real bills reconciled to the cent against their interval data. You can run the same reconstruction 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 rate legible, nothing more.