The short answer
Eligible electricity and gas accounts can have different supply choices. Start with the delivery utility and customer class, not the statement that Illinois is deregulated.
The decision this guide helps you make
Determine whether you have ComEd/Ameren electricity, a municipal/cooperative system, or a gas account under a specific choice or transportation program.
Evidence to gather before deciding
Find the delivery utility, commodity, service class and supplier on the current bill. Then consult the official utility or ICC program.
The detail that is easy to miss
Municipal aggregation is not the same as municipal ownership of the wires. A city can organize a supply arrangement for eligible accounts without being the delivery utility.
Distinguish three different arrangements
Decision case · figures, where used, are hypothetical
Retail supply selection changes an eligible account's supply. Municipal aggregation organizes purchasing under a program. A municipal electric utility operates its own delivery system. Similar words do not make the structures interchangeable.
What would make this decision ready?
Start with the delivery company, then identify any supplier or aggregation arrangement. Neither competitive supply nor aggregation replaces the delivery utility's local wires or outage-response role.
Build a comparable cost basis
Start with one billing period and keep the account and usage constant. Multiply the offered cents per kWh by monthly kWh and divide by 100, then add the supplier fees and any separately priced components. Repeat for the other offer. If a component is unknown, label it unknown instead of silently entering zero. A quote that fixes energy but leaves capacity variable does not have the same risk as one that includes both. Expected cost and cost certainty are separate comparisons.
Read the agreement behind the price
A pricing schedule and the general terms work together. Check the delivery start, term, renewal language, customer obligations and provisions for changes in law or load. Identify whether a number is fixed for the whole term, reset at a stated interval or reconciled later. Obtain explanations in writing. Ask what happens if the business closes, moves, changes operating hours or replaces major equipment; do not assume the lease and supply agreement end together.
Separate supply from utility delivery
The utility continues to maintain the distribution system and handle outages. Supplier shopping does not eliminate regulated customer charges, every demand charge or taxes. Use the price applicable to your service class and product. Residential price-to-compare information can explain concepts, but it is not a commercial quote. If two consecutive bills differ, inspect billing days and consumption before attributing the full dollar difference to a supply rate.
A worked cost comparison
Illustrative inputs, not Illinois market offers: 25,000 kWh per month, offer A at 8.5 cents/kWh with no monthly fee, and offer B at 8.1 cents/kWh with a $35 monthly fee. A models to $2,125 and B to $2,060 for those supply components. The $65 monthly difference becomes $1,560 over 24 identical months. This excludes delivery, taxes, unentered pass-throughs and load changes. B reaches the same modeled cost as A at 8,750 kWh per month. Use your own data in the offer calculator.
| Record | Why it matters | How to verify |
|---|---|---|
| Account and scope | Keeps the decision tied to the right service and customer. | Use the current utility, meter and customer class; keep account identifiers private. |
| Period and units | Prevents comparisons across different months or measures. | Write down billing days and whether the amount is kWh, kW, therms or dollars. |
| Written terms | Distinguishes a claim from an obligation. | Save the full proposed agreement, tariff or program notice and its date. |
| Unknowns and exclusions | Shows what the estimate cannot establish. | List unresolved charges, eligibility and operating assumptions before deciding. |
Use a tool without sending your numbers
A calculator is useful for checking an assumption, not for confirming a tariff, incentive or legal interpretation. Enter only nonidentifying figures in the relevant worksheet. If you need a human review, describe the question and utility first; do not paste an account number or confidential document into the inquiry. Keep the model alongside the written terms so an apparently precise output is not mistaken for a complete quote.
Electricity offer comparison calculator ↗
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Sources & further checks
Primary references checked for this guide on October 15, 2026. Follow the source for current tariffs, eligibility and program terms; rates here are not live offers.