ComEd's Purchased Electricity Adjustment (PEA): How It Moves Your Monthly Bill

If you take ComEd's default electricity supply, one of the more puzzling entries on your commercial bill is the Purchased Electricity Adjustment, usually shortened to PEA. It moves around, it can be a charge in one month and a credit in another, and it never appears in the sales pitch a competitive supplier makes. Understanding what it does, and equally important, what it does not do to an account on a fixed supply contract, is part of reading a ComEd bill accurately.

The PEA lives on the supply side of the bill, which is the shoppable side. To keep the two halves of the bill straight before going further, it helps to have the delivery-versus-supply split clear in your mind, and to know where every line item sits from the field-by-field bill guide.

What the PEA actually reconciles

When ComEd serves you as your default supplier, it has to go out and procure electricity on your behalf. It does that through a mix of purchases arranged in advance, and the actual cost of that supply is not perfectly predictable. Meanwhile, ComEd charges default-supply customers a posted supply rate that is set ahead of time.

Those two numbers, what ComEd paid to procure default supply and what it collected through the posted rate, rarely match exactly. The PEA is the mechanism that trues up the difference. When ComEd collected more than it paid, the reconciliation can flow back as a credit. When it paid more than it collected, the reconciliation shows up as a charge. Over time the mechanism is designed to reconcile the gap rather than let it accumulate. This is a pass-through reconciliation, not a profit margin: ComEd is a wires company on the delivery side and, for default-supply customers, a cost-recovery conduit on the supply side.

Who it applies to, and who it skips

The PEA applies to accounts taking ComEd default supply, also described as utility supply or the basis for the price to compare. If ComEd is the entity buying your electricity, you are inside the default-supply procurement that the PEA reconciles.

It does not apply to the commodity cost of an account served by an Alternative Retail Electric Supplier (ARES). That account is not being served by ComEd's default procurement at all, so there is no default-supply cost-versus-collection gap to reconcile on its supply charge. The distinction matters: the PEA is not a universal ComEd rider that everyone pays. It is specific to the default-supply relationship. An account that has switched to a competitive supplier still receives delivery service from ComEd, and still pays delivery-side riders, but its commodity is priced by its supplier, not by the default-supply mechanism the PEA trues up.

Why it moves month to month

The PEA changes because it is reconciling a moving target against a fixed posted rate. Several things push it around:

• Market conditions. The cost of the electricity ComEd procures for default service reflects wholesale market prices, which vary over time. When procurement costs run above or below what the posted rate assumed, the reconciliation shifts.
• Timing of reconciliation. Because the posted supply rate is set in advance and actual costs come in later, there is always a lag being trued up. That lag is what the PEA closes, and it closes by different amounts in different periods.
• Direction can flip. There is nothing that guarantees the PEA is always a charge. Depending on how collections and costs line up, it can appear as a credit in one month and a charge in another. Do not assume the sign will be the same period to period.

For the actual current values, the primary source is ComEd's own rates and rules material and the account's bill for the period in question. This guide deliberately does not quote a rider value, because a number printed here would be stale the moment the reconciliation moved. Always read it off the live source.

What this means for a fixed ARES contract

This is where the PEA becomes a genuine decision point rather than a curiosity. If you sign a fixed-rate supply contract with an ARES, your commodity price is defined by that contract. The default-supply reconciliation that the PEA performs is not part of a fixed ARES supply price, because you are no longer being served by ComEd's default procurement.

That is one of the practical attractions of a fixed supply contract: it removes the month-to-month movement of the default-supply reconciliation from your commodity cost, replacing it with a known rate for the contract term. It does not, however, freeze your entire bill. Your delivery charges and delivery-side riders continue under ComEd's tariff regardless of supplier, so a fixed supply contract fixes the supply side, not the whole invoice. Read any fixed offer carefully for pass-through language, because a supply product that still passes certain costs through is not fully fixed even if it removes the PEA. The framework for reading those terms is in the guide on fixed versus index commercial electricity.

How to treat the PEA when you review bills

When you build a bill history for procurement, give the PEA its own column rather than burying it inside a blended supply number. Because it can swing between charge and credit, it can make one default-supply month look unusually high or low for reasons that have nothing to do with your usage or a rate change. Isolating it keeps your month-to-month comparison honest and keeps your supply-only effective rate meaningful. This is the same discipline behind separating capacity, energy, and transmission and behind a structured commercial utility bill review.

If you are weighing whether to stay on default supply or move to a competitive contract, the PEA is one reason default-supply cost is not a single fixed number you can lock in your budget. It reconciles over time, which is useful context when you compare ComEd's default supply against a fixed ARES offer using the price to compare as your benchmark. The broader commercial electricity overview puts that choice in context.

Sources

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

The PEA reconciles ComEd's default-supply costs; it is not a savings lever and not a fixed figure. Verify the current rider value on your bill and ComEd's posted materials before drawing budget conclusions.