Illinois Electricity Rates per kWh: ComEd, Ameren and the Price to Compare

In May 2026 the Illinois average leapt to 23.85¢ and fell back a month later. One small line on ComEd bills, worth +8.166¢ that month, fits the jump. The price to compare is not the whole price, and a supplier has to beat both.

The month Illinois hit 23.85¢, and the line that caused it

Illinois’s average jumped from 20.47¢ in April 2026 to 23.85¢ in May, then fell to 19.89¢ in June. State averages rarely move like that. The likely cause sits on a line most people skip: the Purchased Electricity Adjustment.

The adjustment settles the gap between what a utility spent on power and what it collected, month by month. It goes on top of the price to compare, and most months it is small. In May 2026, the state’s historical list shows it at +8.166¢ for ComEd, on a 9.66¢ price to compare. At the statewide average of 514 kWh that month, it adds about $42. In December 2025 Ameren Illinois went the other way, at −4.996¢.

Over a whole year these lines do matter. We billed the average Illinois home’s 8,366 kWh for September 2025 to August 2026 on each utility’s supply prices.

That changes how to judge a supplier. A fixed contract replaces both lines. So an offer that looks a shade above the price to compare may have beaten ComEd last year, and one a shade below may have lost to Ameren. The adjustment cannot be known in advance, and the newest ComEd entry, labelled October though it appears to be November, is +3.798¢.

ComEd jumped 53% in one June

The base price has been far less stable than it looked for years. ComEd sat near 6.8¢ for two years, then the June 2025 summer price landed at 10.028¢, up from 6.552¢ the month before, as PJM capacity costs arrived.

The Ameren column deserves a second look. Its summer price falls away each October, but this year’s winter drop is much smaller. At 10.441¢, the first 800 kWh cost about 24% more than last October’s price, the Citizens Utility Board said, and about 8% less than this summer’s. Ameren’s vice president for regulatory policy said supply prices remain elevated.

ComEd’s 10.103¢ runs from 1 October 2026 to 31 May 2027, made up of 8.413¢ supply and 1.69¢ transmission. The transmission part changes in January 2027, so check the figure after New Year. Ameren’s runs to May as well.

Ameren’s 800 kWh line changes the sums

From October to May, Ameren charges 10.441¢ for the first 800 kWh in a month and 8.262¢ above it. ComEd has one price. Set side by side, supply costs flip near 950 kWh.

Nobody can pick their utility, so the real use of this table is against supplier offers. A flat 10¢ deal looks better than 10.441¢, but it saves only $3.53 on the first 800 kWh, then loses 1.74¢ on every kWh after. Past about 1,000 kWh a month, it costs more than Ameren. Electric-heat homes in central and southern Illinois should test any flat offer on a January bill.

Try a quote on your own bill

Pick ComEd or Ameren Illinois to bring in delivery, then type a supply rate. For a true comparison with your default, add the adjustment on your latest bill to the price to compare, since a contract would replace both.

$2.37 billion over eleven years

Illinois is one of the few states that tallies this officially. Citizens Utility Board’s review of the Illinois Commerce Commission’s yearly reports finds residential customers paid suppliers about $2.37 billion more than the utility price from June 2015 to May 2026.

In only one area and one year did supplier customers come out ahead: Ameren’s, in 2022 to 2023, when they saved $66.3 million. In the latest year, supplier customers paid about 1.28¢ per kWh over ComEd’s price and 3.05¢ over Ameren’s. About 1.14 million households had a supplier in May 2026: 715,750 at ComEd and 421,710 at Ameren, of whom 39% and 62% were in municipal aggregation.

EIA’s 2025 survey points the same way. Counting aggregation, 1,208,945 supplier homes averaged 19.59¢ per kWh where default prices came to 17.25¢: $213 each and $258 million in all.

Worked out from EIA-861 for 2025: suppliers’ revenue from homes plus the utilities’ delivery-only revenue, divided by the kWh, against the same kWh at each utility’s default-service price per kWh. Aggregation programmes count as suppliers. The averages hide wide differences between contracts.

Aggregation, suppliers and leaving

A town’s aggregation deal may be competitive or not, so do not assume. Chicago’s programme ended in 2015, and towns can end theirs and return residents to the utility. Plug In Illinois lists the current programmes along with supplier offers.

EIA-861 for 2025, Sales to Ultimate Customers (residential): every utility, supplier and retail provider’s own report.

Ask three things of any seller: the rate, how long it lasts and what follows it. Then compare against the price to compare for the same months, summer and winter both.

ComEd and Ameren, all in

All-in default prices were close in 2025: 17.71¢ per kWh at ComEd and 16.70¢ at Ameren. Delivery for supplier homes ran to 8.89¢ and 8.77¢. Springfield, Naperville and other city systems paid less.

— in the last two columns: the utility reported no homes on delivery-only service to EIA for 2025, so none of its homes bought power from a supplier. 9 of the 10 are city utilities, public districts or co-ops.

EIA-861 for 2025: each utility’s revenue from homes divided by the kWh they used, so monthly charges are spread into the price.

Twice the bill in July

July 2026’s average bill of $193 was almost twice April’s $110. Chicago’s air conditioning season is also when the higher summer supply price applies, and Ameren has no lower block then, so high use costs more just as it peaks.

Nuclear power and the 2025 break

From 11.53¢ in 2010 to 18.91¢ over the last 12 months is 64%. More than half of the state’s generation is nuclear, and that held prices near the US average until 2025’s capacity shock.

A low bill for a Midwest state

Illinois is 2nd of 5 in the East North Central states and 5% above the national price. Its modest use leaves the typical bill 38th of 51.

Across the border: Kentucky 13.95¢, Missouri 13.97¢, Iowa 14.20¢, Indiana 16.90¢, Wisconsin 18.79¢.

All 50 states and DC on one page, with a map.

How the year test works

We took EIA’s statewide average household for each month, priced it on the commission’s history for residential non-space-heat customers, and applied Ameren’s 800 kWh line when it was in force. Two limits: the statewide home is not a real ComEd or Ameren home, and the adjustment is billed on a lag, so a month’s line may not match a month’s use exactly. Space-heat rates differ. The history file shows two rows dated October 2026; we read the first as November.

We cannot prove the adjustment caused all of May’s spike, since EIA reports revenue by month rather than by line, but the timing and size fit. The June 2023 move in the same series matches ComEd’s price falling from 9.665¢ to 6.809¢.

Figures to August 2026 (EIA marks recent months preliminary), utility figures for 2025, refreshed 3 November 2026. How every number in this series is made and checked.

• Illinois, every month since 2010 (CSV): price per kWh, kWh and bill per home, and the US price.
• Every state, DC and the US (CSV)
• Everything above with the utility and supplier figures (JSON)

EIA data is in the public domain: credit the U.S. Energy Information Administration. A link back is welcome.

Questions

Electricity rates in other states

Version history

• 2.0 (6 November 2026): rebuilt from the Commission’s price history: the Purchased Electricity Adjustment and a year’s effect, ComEd and Ameren prices since 2023, Ameren’s 800 kWh line against flat offers, and supplier losses by year.
• 1.0.1 (November 2026): wording and page heading tidied; no figures changed.
• 1.0 (November 2026): first published.