Illinois Business Electricity Rates: ComEd vs Ameren

The most important fact about an Illinois business electricity “rate” is that it is not one number. A bill combines utility delivery, electricity supply, transmission, capacity, taxes, and adjustments. Some components vary by utility territory, customer class, usage pattern, and the account's capacity or transmission obligation.

This guide explains the comparison framework. It deliberately does not copy a single live rate into the page because utility rates and riders change. For the current utility-supply values, start with the Illinois Power Agency electricity supply rate page, then verify the applicable tariff and bill class with ComEd or Ameren Illinois.

ComEd and Ameren are different markets

ComEd serves much of northern Illinois and participates in PJM. Ameren Illinois serves much of central and southern Illinois and participates in MISO. That distinction matters because the capacity market, transmission framework, default-supply procurement, and tariff language are not interchangeable.

Question	ComEd account	Ameren Illinois account
Regional market	PJM	MISO
Utility supply source for eligible small customers	Illinois Power Agency procurement	Illinois Power Agency procurement
Current public rate starting point	IPA plus ComEd tariff/rate resources	IPA plus Ameren business rates
Capacity concept	PJM capacity obligation and account PLC	MISO resource-adequacy constructs and tariff treatment

Never apply a ComEd price, capacity explanation, or savings estimate to an Ameren account without rebuilding the analysis from the Ameren bill and tariff.

Utility supply is a benchmark, not the entire bill

Illinois allows eligible customers to buy supply from a competitive retail electric supplier while the utility continues delivery, metering, and outage response. The utility-supply benchmark is useful, but the correct comparison depends on eligibility and the specific charges included in each offer.

The Illinois Power Agency's annual procurement plan is designed for residential and small commercial default-service load. A larger commercial account, or an account on a different utility service, may not be comparing against the same product.

Before comparing an alternative retail electric supplier, record:

1. Utility and service class.
2. Annual kWh and monthly peak kW.
3. Current supply status and contract end date.
4. Utility price-to-compare components for the applicable period.
5. Whether the supplier price includes energy, capacity, transmission, renewable obligations, line losses, and ancillary charges.
6. Taxes, pass-throughs, change-in-law provisions, and early termination terms.

Why the advertised cents-per-kWh can mislead

A fixed supplier price may exclude items that later appear as pass-through charges. A utility benchmark can also contain adjustments that move from month to month. Two offers with the same headline price can therefore have different expected costs and risk.

Use an annualized comparison:

Expected annual supply cost = fixed volumetric charges + demand or capacity charges + transmission + monthly fees + modeled pass-throughs

Then run at least three scenarios. The base case uses the expected load. A high-usage case should reflect plausible production or weather growth. A stress case should model the largest uncapped pass-through or index exposure in the contract. Do not call the lowest base-case quote the winner until the stress case and contract language are reviewed.

How to read a price trend without being misled

A "trend" is only meaningful when the thing being measured stays constant. The most common mistake in tracking Illinois commercial energy prices is splicing together numbers that are not the same measurement — comparing an all-in bill rate from one month against a supply-only quote from another, or comparing a period on utility default supply against a period on a retail contract with different included components. When the definition of the number changes, the apparent "trend" is an artifact of the accounting, not a real movement in cost.

To read a trend correctly, fix three things before you compare anything:

1. Scope. Decide whether you are tracking supply-only cost, all-in cost, or a single component (for example, the volumetric energy charge). Then hold that scope constant across every point in the series.
2. Basis. Convert to a consistent unit — cents per kWh for electricity, cents per therm for gas — and note whether the figure is a bill result (dollars divided by usage) or a forward quote for a future term. These answer different questions and should never share an axis without labeling.
3. Time reference. A bill covers a past service period. A supplier quote is for a future delivery period. A wholesale forward is the market's current price for a future month. Mixing "what I paid," "what I'm being offered," and "where the market is" produces a chart that looks precise and means nothing.

Where the primary data actually lives

There is no single page that publishes "the" Illinois commercial rate, and any site that claims one is oversimplifying. The defensible sources are layered:

• Utility default supply (price-to-compare). The Illinois Power Agency electricity supply rate page is the starting point for the default-service benchmark that eligible customers are measured against. The IPA's procurement plan explains how that default supply is bought.
• Delivery and rider values. ComEd rates and rules and Ameren Illinois business rates carry the tariff and rider figures that supply shopping does not change.
• Wholesale market context. PJM (for ComEd's region) and MISO (for Ameren's region) publish market and capacity information. Treat these as context for direction and volatility, not as bill rates.
• Hourly and interval concepts. ComEd's Hourly Pricing program is a useful official explanation of how hourly wholesale energy prices behave, even for accounts that are not enrolled.

Because these sources update on their own schedules, always date the figure you pull and note the effective period. A "current" number captured six months ago is historical data now.

What drives changes over time

Illinois commercial electricity costs can change because of:

• wholesale energy forwards and spot prices;
• PJM or MISO capacity and transmission outcomes;
• the account's measured peak contribution;
• line-loss factors and utility riders;
• renewable and clean-energy compliance charges or credits;
• supplier risk premiums and credit terms;
• load-shape changes, not just total consumption.

The most defensible “trend” chart is built from the account's own bills using consistent components. Separate delivery from supply. Record adjustments and credits in their own columns. If a component changes definition, note the tariff effective date instead of splicing it into an older series as though it were identical.

A practical monthly tracking table

For each bill, capture service dates, kWh, peak kW, supply dollars, delivery dollars, taxes/other, total dollars, and supplier. Calculate supply-only cents per kWh and all-in cents per kWh separately. A falling supply rate can be offset by higher delivery or peak-related charges; only the component-level table makes that visible.

Common mistakes when interpreting price movement

• Reacting to spot instead of forward. A single spot or day-ahead print is weather- and grid-driven and can swing hard without saying anything about a 12- or 24-month contract price. Suppliers price fixed terms off the forward curve, not off yesterday's spot.
• Confusing a capacity auction result with a rate. A PJM capacity auction clearing price is an input to future capacity cost, not a line on a bill. It flows into supply cost over time and interacts with an account's own peak contribution (its capacity tag, or PLC), so two accounts in the same territory can feel the same auction differently.
• Ignoring the delivery side. Supply shopping does not touch delivery, most riders, or taxes. A falling supply market can coincide with rising delivery charges, so a supply-only trend can point one way while the all-in bill points the other. Only a component-level table (see the tracking table above) shows which is happening.
• Assuming the sign of adjustments. Reconciliation and clean-energy mechanisms can appear as either charges or credits depending on program and market conditions. Do not assume a line that was a credit last year will be a credit this year.
• Treating "the market is up" as a decision. Direction alone does not justify a signature. The account's renewal window, risk tolerance, and the fully-loaded, matched comparison of specific offers drive the decision.

How to apply this to a real account

The most defensible view of an account's price history comes from the account's own bills, not from a headline index. Build the component-level table described above, then use it to answer three questions: Is my supply cost moving, or is it delivery? Is the movement a real market change or a change in what the number includes? And where does my current position sit relative to the utility default benchmark for the same service period? From there, the decision follows a process, not a headline — see commercial energy procurement for the full framework, commercial electricity in Illinois and commercial natural gas in Illinois for the market structure behind these prices, and the renewal timeline for when to act.

Decision rule

A retail offer is supportable when its expected total cost and risk are preferable to the applicable utility alternative, after matching the same service period and charge scope. “Market prices are rising” is not enough. The recommendation should name the benchmark, assumptions, excluded charges, contract risks, and date the offer expires.

Sources

• Illinois Power Agency — Electricity Supply Rates
• Illinois Power Agency — Electricity Procurement Plan
• ComEd — Rates and Rules
• Ameren Illinois — Business Rates
• ComEd Hourly Pricing
• PJM
• MISO

Source check date: August 1, 2026. Rates and tariffs can change after publication; verify the linked primary sources for the account and billing period.