Commercial Natural Gas in Illinois: Suppliers, Rates & Utilities

Commercial natural gas in Illinois works much like electricity: an eligible business can buy the gas supply from a competitive supplier while the utility continues to deliver it — but the gas utility, and even whether supplier choice exists, depends on where the facility sits. This page maps the territories and explains what a real gas quote requires.

Who this is for

Businesses with meaningful heating, process, or hot-water gas load — manufacturers, food service and processing, hotels and multifamily, laundromats, and any facility where therms are a real line item. It is written for the people who sign the contract: facilities, operations, and finance.

Know your gas utility first

Unlike electricity (two dominant delivery utilities), Illinois gas is split across several:

• Peoples Gas — the City of Chicago only.
• Nicor Gas — much of northern Illinois outside Chicago (600+ communities).
• North Shore Gas — a narrower set of Lake County and far-north communities from roughly Winnetka to the Wisconsin line (Waukegan is on North Shore Gas, not Nicor).
• Ameren Illinois — much of central and southern Illinois.

Some communities straddle a boundary — Buffalo Grove, for instance, has areas served by both Nicor and North Shore Gas — so the only reliable answer for a specific address is the utility name printed on a recent bill.

Where supplier choice exists — and where it works differently

In Nicor, Peoples, and North Shore territory, eligible commercial customers can contract with a licensed alternative gas supplier while the utility delivers the gas and handles safety and emergencies. In Ameren Illinois gas territory the model is different: there is no standard small-commercial supplier-choice program, and only larger non-residential customers can self-supply through Ameren's Rider T transportation service. On this site we do not describe a "switch your gas supplier" path where it does not exist.

Supply vs. delivery for gas

The supply charge is the commodity — often quoted per therm, and on utility service tied to a purchased-gas cost that adjusts over time. The delivery charge covers the utility's distribution system, metering, and applicable riders and taxes. A supplier contract prices the supply portion; delivery stays with the utility under its tariff. As with electricity, don't apply a supply-price difference to the whole bill.

What drives a commercial gas price

• Therm usage and seasonality — most commercial gas load is heavily winter-weighted, which shapes how a term is priced.
• Load profile and interruptible/transportation status — larger accounts may qualify for transportation service with different economics.
• Contract term, start month, and market timing.
• Applicable taxes and utility riders.

What a commercial gas quote requires

A recent bill and account number, the service address and gas utility, at least twelve months of therm usage (to capture the seasonal shape), and the current contract's end date. For larger or transportation-eligible accounts, the utility rate class and any interruptible terms matter. Start with the Chicagoland natural gas procurement guide, then request pricing with the documents in hand.