ComEd Delivery vs Supply: Reading the Split on a Commercial Bill

A ComEd commercial bill is really two bills printed on the same page. One side is the electricity commodity, which an eligible business is free to buy from ComEd's default service or from a competitive retail supplier. The other side is the regulated cost of delivering that electricity, which stays with ComEd no matter whose commodity flows through the wires. Reading the bill through this delivery-versus-supply lens is the single most useful habit a commercial buyer can build, because almost every procurement mistake starts with blurring the two.

This guide is not a field-by-field walkthrough of every line item. For that, see the companion guide on how to read a ComEd commercial electric bill. Here the goal is narrower and more strategic: learn to draw one clean line down the middle of the bill, understand what sits on each side, and use that split to avoid the most common way businesses overstate savings.

The two sides of the bill

Supply is the commodity, the actual kilowatt-hours your facility consumes. This is the shoppable side. Under Illinois retail electric choice, an eligible commercial account can leave ComEd's default supply and buy the same electricity from an Alternative Retail Electric Supplier (ARES). The electrons are identical; only the price and contract terms of the commodity change. The mechanics of that choice are covered in how commercial electricity choice works in Illinois and in the broader commercial electricity overview.

Delivery is everything ComEd charges to own, maintain, and operate the poles, wires, transformers, and meter that bring power to your door, plus the metering and customer service around your account. ComEd remains your delivery utility whether you take default supply or sign with an ARES. Delivery charges are set through ComEd's tariff, which is reviewed by the Illinois Commerce Commission, not negotiated with you. That is why they do not disappear or shrink when you switch suppliers.

What sits in each bucket

On the supply side you will typically find the commodity charge for your kilowatt-hours and, depending on how supply is presented, embedded costs for capacity and transmission. If you take ComEd default supply, this side also carries ComEd's supply-related adjustments, including the Purchased Electricity Adjustment (PEA), which trues up what ComEd paid for default supply against what it collected. If you are on an ARES contract, the supply side instead reflects your contracted rate and any pass-through terms your agreement allows.

On the delivery side you will generally find a customer charge, distribution charges tied to your usage or your billed demand in kilowatts, metering charges, and a set of riders that recover specific program and reconciliation costs, along with applicable taxes and local fees. These riders recover things like energy-efficiency and renewable-program costs that ComEd is authorized to collect. They ride with delivery because they fund the regulated utility's obligations, not the commodity you buy.

The reason capacity and transmission can feel confusing is that they are wholesale cost drivers that can show up embedded inside a supply price. It helps to keep the three supply components straight, which is the subject of the capacity, energy, and transmission three-buckets guide. For the delivery side, note that a demand charge bills the peak kilowatts your facility pulls and lives in delivery, while the capacity tag (Peak Load Contribution) carries your peak into supply cost. They both reflect peak behavior but sit on opposite sides of the line. The distinction matters enough to have its own guide on commercial demand charges.

Why only supply is shoppable

Retail choice in Illinois opened the commodity to competition but left delivery as a regulated monopoly function. There is only one set of wires into your building, and building a competing set would be wasteful, so delivery stays regulated and priced through an approved tariff. Competition was introduced where it can actually work: the commodity, which any qualified supplier can sell.

The practical consequence is simple. When a supplier quotes you a price, that price can only move the supply side of your bill. It cannot touch distribution, metering, riders, or taxes. A genuinely good supply decision lowers your commodity cost or locks in price certainty for the commodity; it does nothing to the delivery charges, which continue exactly as ComEd's tariff dictates.

How the split prevents overstating savings

Here is the error the delivery-versus-supply lens is built to prevent. Suppose your total monthly bill is dominated by delivery charges, and a supplier offers a commodity rate lower than ComEd's default supply. If someone multiplies that per-kilowatt-hour difference by your usage and then talks about it as a percentage of your whole bill, the math is wrong. The difference only applies to the supply portion. Delivery, riders, and taxes were never in play.

The disciplined approach is to compute a supply-only effective rate, sum every supply-section dollar and divide by billed kilowatt-hours, and compare that against the offer on the same basis. Hold the delivery side entirely separate. When you do this, you compare like against like: the ARES commodity price against ComEd's default supply price, for the same service period, on the same load. This is also why the price to compare exists, it is the utility-supply benchmark you measure an offer against, not the whole-bill total.

A clean split also protects you against contract surprises. A "fixed" supply offer that quietly passes through capacity or transmission is not fixed on the whole supply side, and you can only see that if you already know which costs live in supply versus delivery.

A quick method you can repeat

1. Draw the line. Find where the bill separates supply charges from delivery charges. On a ComEd default-supply bill, the supply section and the PEA belong on the supply side; the customer charge, distribution, metering, and riders belong on the delivery side.
2. Total each side separately. Never net a supply credit against a delivery charge, or vice versa.
3. Compute the supply-only rate. Divide total supply dollars by billed kilowatt-hours.
4. Benchmark supply against supply. Compare your supply-only rate or ComEd's default supply price against any ARES offer, for the identical period.
5. Leave delivery out of the comparison. Report it as a fixed backdrop that the supplier decision does not change.

Run this the same way every month and your bill history becomes comparable end to end, which is the whole point. If the account also buys natural gas, the same logic applies on the commercial natural gas side, where supply and delivery are similarly split. When you are ready to formalize the read across many bills, a structured commercial utility bill review turns the split into a decision.

Where Ameren fits

The same delivery-versus-supply structure applies to Ameren accounts in central and southern Illinois, and to ComEd accounts in the north, though the specific rider names, tariff labels, and market context differ because ComEd sits in PJM and Ameren in MISO. The lens travels; the line items do not always match. Always let the actual bill and the current tariff control for the period you are analyzing.

Sources

• ComEd — Billing, Payment, Rates and Rules
• Illinois Commerce Commission
• Illinois Power Agency — Electricity Supply Rates

This guide explains how the bill is structured so you can compare supply offers on equal footing. It does not promise any particular savings; verify current ComEd tariffs and your own bill period before acting.