Illinois Electricity Suppliers by Utility Territory: ComEd vs Ameren Illinois (2026 Guide)

Illinois is one of the most active deregulated electricity markets in the Midwest, but your options depend on which of the state’s two major electric utilities serves your area. Commonwealth Edison (ComEd) serves northern Illinois including Chicago, while Ameren Illinois covers the central and southern parts of the state. This guide explains how electricity deregulation works in each territory and how to find the best supplier for your area in 2026.

Illinois Electricity Deregulation: The Basics

Illinois deregulated its retail electricity market through the Electric Service Customer Choice and Rate Relief Law of 1997. Under deregulation, residential and small commercial customers can choose their electricity supplier — called an Alternative Retail Electric Supplier (ARES) — while their local utility continues to deliver power through its wires and responds to outages. Your bill is split into supply charges (what you pay for electricity) and distribution charges (what you pay the utility for delivery).

The Illinois Commerce Commission (ICC) regulates ARES companies and maintains a list of licensed suppliers. The Illinois Power Agency (IPA) also plays a role, setting procurement processes for customers who don’t choose an ARES and remain on utility default service.

ComEd Territory: Northern Illinois and Chicagoland

Commonwealth Edison serves approximately 4 million customers across northern Illinois, including the City of Chicago, the entire Chicago metropolitan area (Cook, DuPage, Lake, Kane, McHenry, Will, Grundy, DeKalb, and Kankakee counties), plus portions of the I-80 corridor. If your address is in Chicago or any suburb north of roughly I-80, ComEd is your delivery utility.

ComEd’s territory is the most competitive electricity market in Illinois and one of the largest in the Midwest. Dozens of licensed ARES companies compete for ComEd customers, including Constellation Energy, Ambit Energy, Verde Energy, CleanChoice Energy, Spark Energy, and Homefield Energy. Because of Chicago’s population density and commercial activity, ARES companies offer the widest variety of products — fixed-rate contracts, green energy plans, time-of-use pricing, and bundled services — in the ComEd zone.

Customers who don’t choose an ARES remain on ComEd’s Hourly Pricing or Fixed Price options. ComEd’s fixed price is set quarterly by the IPA and serves as a useful benchmark: compare any ARES offer to ComEd’s current quarterly rate before signing. You can find ComEd’s current default supply rate at ComEd.com or by calling ComEd customer service.

Ameren Illinois Territory: Central and Southern Illinois

Ameren Illinois serves approximately 1.2 million electric customers across central and southern Illinois, including Springfield, Peoria, Decatur, Champaign-Urbana, Rockford (partially), Bloomington-Normal, and communities down to the Missouri and Kentucky borders. If you live south of the I-80 corridor outside of Chicago’s suburbs, Ameren Illinois is almost certainly your utility.

Ameren Illinois’s territory has fewer ARES options than ComEd’s, but major national suppliers do operate here. Constellation, Verde Energy, Spark Energy, and a handful of regional suppliers offer fixed-rate supply contracts for Ameren residential customers. Green energy products are available but less numerous than in the ComEd zone.

Ameren Illinois customers on default service receive supply through the IPA’s annual competitive procurement process. Like ComEd’s quarterly rate, the Ameren IPA procurement price serves as a useful baseline when comparing ARES offers. Because Ameren Illinois’s territory includes a mix of urban and rural customers, the default service pricing can vary from ComEd’s — don’t assume they’re comparable.

How to Compare ARES Companies in Illinois

The Illinois Commerce Commission maintains an online Apples-to-Apples comparison tool at the Illinois Power Agency website (illinoisenergymatters.net) that lists licensed ARES companies and their current rates for each utility territory. To use the tool effectively, you’ll need your utility account number (to confirm your service territory) and your average monthly usage in kilowatt-hours (found on your bill).

Key factors to evaluate when comparing ARES offers in either territory include the supply rate in cents per kWh, whether the rate is fixed or variable, the contract term (month-to-month, 6-month, 12-month, 24-month), any enrollment or cancellation fees, and whether green energy certificates are included. Variable-rate ARES contracts can start attractively but expose you to market price volatility — fixed-rate contracts are generally better for budget predictability.

Green Energy Options in Illinois

Illinois passed the Climate and Equitable Jobs Act (CEJA) in 2021, setting a goal of 100% carbon-free electricity by 2050 with aggressive interim targets. Several ARES companies offer 100% renewable supply products backed by Renewable Energy Certificates (RECs) from wind and solar projects — Illinois has substantial wind resources downstate that make in-state RECs relatively affordable. CleanChoice Energy, Constellation’s green products, and Verde Energy all offer renewable options in both ComEd and Ameren Illinois territories. Premiums for 100% renewable supply are typically 1–2 cents per kWh above standard rates.

Switching Between Utilities: What’s Not Possible

One important limitation: you cannot switch your delivery utility. If you live in ComEd territory, ComEd delivers your electricity — period. If you’re in Ameren Illinois territory, Ameren Illinois delivers it. You can only switch your electricity supplier (the ARES), not the wires and infrastructure company. This is true throughout Illinois regardless of which territory you’re in.

FAQ

How do I know if I’m in ComEd or Ameren Illinois territory?

Check your electric bill — the utility name is prominently displayed. You can also look up your address on the ICC’s website or use the Illinois Power Agency’s Apples-to-Apples comparison tool, which asks for your utility as a first step.

What happens to my utility if I sign up with an ARES?

Your utility (ComEd or Ameren) continues to deliver power to your home. They also continue to handle outages, meter reading, and billing. You simply pay a different company for the electricity supply portion of your bill. In many cases, your ARES bill appears as a separate line item on your ComEd or Ameren statement.

Can I switch back to my utility’s default service?

Yes, at any time — with proper notice as specified in your ARES contract. Month-to-month contracts typically allow 30-day notice with no penalty. Fixed-term contracts may have early termination fees.

Is there a consumer protection office for Illinois electricity complaints?

Yes. The Illinois Commerce Commission handles complaints against ARES companies and utilities. You can file a complaint at icc.illinois.gov or by calling the ICC’s Consumer Affairs division. The Citizens Utility Board (CUB) also provides free advocacy and counseling for Illinois electricity customers.

Do ARES savings vary by season?

Yes. Electricity wholesale prices are higher in summer (peak cooling season) and can spike in winter cold snaps. If you’re on a variable-rate ARES contract, you’ll feel those fluctuations. Fixed-rate contracts smooth out seasonal variation — if you sign in a low-price period (spring or fall), you can lock in a good rate for 12–24 months.

Bottom Line

Whether you’re in ComEd’s Chicagoland territory or Ameren Illinois’s downstate service area, the mechanics of electricity choice are the same: identify your utility, benchmark the IPA procurement rate, then use the Apples-to-Apples tool to compare ARES offers. Prioritize fixed-rate contracts with clear terms, and watch for variable-rate products that could expose you to price spikes. Both territories have reputable national suppliers operating — it’s worth spending 15 minutes comparing before your next renewal.