Illinois · Electric
ComEd and Ameren Price to Compare: what it is, when it changes
Written by Judy
· 7 min read
If a salesperson or a letter asks you to "beat ComEd's price" or "save on Ameren," you need one number first: the Price to Compare. In Illinois, that number may not be printed on your bill. Here is what it is, how to work it out, and when it changes.
What is the Price to Compare in Illinois?
In Illinois, you can buy your electricity from a company other than ComEd or Ameren Illinois. The state calls these companies alternative retail electric suppliers. I'll just call them suppliers.
If you never picked a supplier, ComEd or Ameren buys your electricity for you. The Price to Compare is what you pay them for it, per kilowatt-hour. A kilowatt-hour, or kWh, is one unit of electricity. Your bill shows how many you used.
The state's shopping website, Plug In Illinois (opens a new tab), explains how the utility's price is set:
- A state agency called the Illinois Power Agency plans the buying.
- In recent years, the utilities have bought power twice a year, once in the spring and once in the fall.
- The utilities pass the cost on to you "without any mark-up or profit."
So the Price to Compare is not a sales price. It is the utility's cost of buying power for you.
What does it cover?
Plug In Illinois says your bill has three parts:
- Electric supply. The electricity you use.
- Transmission. Moving that electricity over big high-voltage lines to your local area.
- Distribution (delivery). The local wires and equipment that bring it to your home.
For both utilities, the state figures the Price to Compare this way:
Price to Compare = electric supply charge + transmission charge
The delivery charges are not part of it. You pay those to ComEd or Ameren no matter who sells you the electricity. That is why switching can only change part of your bill. My guide to supply and delivery charges walks through each line.
Why can't I find "Price to Compare" on my bill?
Illinois bills may not print a line called Price to Compare. You add two lines together instead. Here is what to look for, according to Plug In Illinois:
- ComEd: In the supply section, find the Electricity Supply Charge and the Transmission Services Charge.
- Ameren Illinois: In the supply section, find the line that starts with Purch Elec (short for purchased electricity) and the Transmission Service Charge.
Adding these up by hand can be tricky, because the bill may split them into several lines. The easy way: Plug In Illinois posts the current number for ComEd (opens a new tab) and for Ameren Illinois (opens a new tab). Our ComEd page and Ameren Illinois page show it too.
What is the Purchased Electricity Adjustment?
You may also see a Purchased Electricity Adjustment in the supply section. It is a small charge or credit that changes every month. It evens out the difference between what the utility paid for power and what it charged customers.
The state leaves it out of the Price to Compare. And if you switch to a supplier, you no longer pay it.
When does the Price to Compare change?
The utility's supply price is set for two seasons:
- Summer: June 1 through September 30.
- Non-summer: October 1 through May 31.
So the Price to Compare changes on June 1 and October 1. It can go up or down.
There is one more change to know about. Plug In Illinois says the transmission charge "usually changes annually," and for both ComEd and Ameren it will change again in January 2027. Since transmission is part of the Price to Compare, the total can shift a little in January too.
Why does Ameren have two winter prices?
From October through May, Ameren's price has two steps:
- one price for the first 800 kWh you use in a month, and
- a lower price for every kWh above 800.
So in the colder months, a home that uses a lot of electricity pays less per kWh for the extra use. That matters when you compare offers. A supplier's single flat price might beat Ameren's first-800 price but lose to its price above 800.
Which season should I compare with?
Plug In Illinois points out that over a year, your average price is likely "somewhere between the summer rate and the non-summer rate." Where it lands depends on how much power you use and in which months.
If a supplier offers one fixed price for 12 months, compare it with your year-round picture, not just this month's price. A price that beats the summer rate may not beat the winter rate, or the other way around.
How do I know if I already have a supplier?
The Citizens Utility Board (CUB), Illinois's consumer watchdog group, says: "Check the 'Supply' section of your bill to see if you're with an alternative supplier."
If a supplier sells you power, its name and price show up there instead of ComEd's or Ameren's supply charges. Most suppliers put their charges on your utility bill. A few send their own bill.
If you live in a town with a city electric program, you may have a supplier without ever signing up yourself. See how Illinois city electric programs work. And my guide Do I have an electric supplier? walks through it step by step.
How do I compare an offer?
- Find your Price to Compare for this season, and think about next season too.
- Get the supplier's price per kWh and ask how long it lasts. Ask if it is a short-term starting price.
- Ask if the price is fixed or variable. A fixed price stays the same for the contract. A variable price can change.
- Ask about a monthly fee. A few dollars a month can erase a small savings.
- Compare. If the offer is lower than the Price to Compare, fees included, you would likely save.
You can see offers for your area on Plug In Illinois (opens a new tab). CUB warns that Illinois homes have lost a lot of money to supplier offers over the years, so it pays to check the numbers before you sign.
Can I go back to ComEd or Ameren?
Yes. Plug In Illinois says the utility "will not charge you a fee" to go back. But you may have to stay with the utility for at least 12 months before you can pick a supplier again. Ask your utility about this before you switch back.
What about the supplier? CUB says Illinois law lets you leave an electric supplier contract without an exit fee. My guide to fees for leaving a supplier early covers how that works in each state.
Who to call
- Illinois Commerce Commission (ICC): 1-800-524-0795
- Citizens Utility Board (CUB): 1-800-669-5556
What to do next
- Let me do the math. Try the free check. Send me a photo of your bill, and I'll compare your price with every offer the state lists for your area, including Ameren's two-step winter price.
- See the current Price to Compare: ComEd or Ameren Illinois, or start from the Illinois page.
- Read more: Illinois city electric programs and Do I have an electric supplier?