Your Ameren Bill Jumped 39% This Summer — and an Auction Set the Price

Updated on September 5, 2026

By Christopher Burg · Last updated August 29, 2026

The Ameren Illinois rate increase pushed the utility’s summer Price to Compare to 11.326 cents per kWh for June 1 through September 30, 2026 — roughly 39% higher than the same period in 2024. The cause sits in a wholesale capacity auction, not in your thermostat. In Illinois, the supply half of that bill is shoppable.

What the Ameren Illinois rate increase actually changed

Ameren Illinois publishes a number called the Price to Compare. The Illinois Commerce Commission tells shoppers to use it as the apples-to-apples benchmark when judging any competitive offer. For the summer 2026 period, that number is 11.326 cents per kWh on the first 800 kWh of usage, effective June 1 through September 30, 2026.

The Price to Compare is not your whole bill. It covers the supply and transmission portion — the part an alternative supplier is allowed to replace. Delivery charges stay with Ameren regardless of who sells you the electricity.

That distinction is the entire point of shopping. The Ameren Illinois rate increase raised the benchmark. It did not change the rule that you are allowed to beat the benchmark.

Why did the Ameren Illinois rate increase happen?

The short answer is an auction held hundreds of miles upstream. The Ameren Illinois rate increase was not decided in Illinois at all.

Ameren Illinois buys capacity through MISO, the grid operator covering the central United States. MISO runs a Planning Resource Auction that sets a price for capacity — the commitment that generation will be there when demand peaks. For the June 2026 through May 2027 planning year, that auction cleared at $424.30 per MW-day. Two years earlier it cleared around $30 per MW-day.

Citizens Utility Board, the state’s consumer watchdog, points to four drivers behind the spike: new and proposed data centers pushing MISO’s forecasted load higher, a pricing methodology called the Reliability-Based Demand Curve that deliberately rewards higher prices with more generation, interconnection queue delays of roughly three and a half years that stall new clean generation, and continued reliance on coal and gas for more than 60% of summer capacity.

None of those are things a household or a small business can influence. All of them show up on the supply line of your bill.

It is worth naming what this is not. The Ameren Illinois rate increase is not a story about anyone using more electricity, and it is not a penalty for a particular kind of customer. It is a wholesale cost, set at auction a year in advance, passed through to every customer who has not chosen a competitive supplier. Ameren does not mark it up. That is precisely why shopping works: you are not negotiating with your utility, you are replacing the pass-through with someone else’s price.

How much is the Ameren Illinois rate increase costing you?

For a residential customer, Citizens Utility Board puts the difference at roughly $16 more per 500 kWh compared with two years ago. Scale that to a business running 10,000 kWh a month and the arithmetic gets serious quickly.

The Ameren Illinois rate increase is also seasonal in shape. Summer rates run higher than winter rates because summer peaks are what the capacity market is priced against. A rate locked in June looks different from one locked in November, which is why timing matters as much as the number itself.

Ameren or ComEd? Illinois runs two different markets

This trips up a lot of Illinois shoppers. The state has two large utilities sitting in two different grid regions:

Ameren Illinois covers central and southern Illinois and buys capacity through MISO. ComEd covers northern Illinois, including Chicago, and buys through PJM — a different grid operator running a different auction on a different schedule. Both regions set records in the same period, but the numbers are not the same and neither are the effective dates.

The Ameren Illinois rate increase applies only to Ameren’s downstate territory. Both auctions set records in the same stretch, and for overlapping reasons — data centers are reshaping load forecasts across the eastern half of the country. PJM’s 2027-28 auction cleared at $333.44 per MW-day, up from $28.92 four years earlier. MISO’s cleared higher still at $424.30. Different operators, different calendars, the same underlying squeeze — and an Ameren Illinois rate increase and a ComEd increase that arrive on separate schedules. What the two share is Illinois retail choice law. In both territories, customers may buy supply from an Alternative Retail Electric Supplier while the utility continues to deliver the power, read the meter, and restore service after a storm.

What you can control about the Ameren Illinois rate increase

You cannot vote on a capacity auction. You can decide who sells you electricity. That is the whole of what a customer controls after an Ameren Illinois rate increase, and it is not nothing. Five steps, in order:

1. Find your current Price to Compare. It is printed on your Ameren bill and posted on the Illinois Commerce Commission’s Plug In Illinois rate board. For summer 2026 it is 11.326 cents per kWh.
2. Compare offers against that number for the same period. A supplier rate that looks good against a winter benchmark may lose against a summer one.
3. Read the term length and the early termination fee before the rate. A low rate on a 36-month contract with a steep exit fee is a different product than the same rate on 12 months.
4. Watch for introductory pricing that resets. The rate that matters is the one you will be paying in month seven, not month one.
5. Calendar the expiration date the day you sign. Contracts that roll to a variable month-to-month rate at expiration are where most of the regret in this market lives.

For a business, add one more: ask whether the offer passes capacity costs through or fixes them. With capacity clearing above $400 per MW-day, that single structural question can matter more than a fraction of a cent on the energy rate.

A commercial account has more leverage against the Ameren Illinois rate increase than a household does. Capacity charges are assigned based on your demand during system peak hours, which means load shifting has a direct dollar value — moving a process off the afternoon peak can lower next year’s capacity obligation, not just this month’s bill. Ask any supplier quoting your account how capacity is billed under the contract, whether the rate is fixed or indexed, and what happens if your peak demand changes mid-term. A supplier that cannot answer those three questions cleanly is quoting you a number, not a strategy.

Timing is the other lever. Because the Ameren Illinois rate increase follows a seasonal reset, the comparison you run in August is against a summer benchmark that expires September 30. Know which period any quoted rate is being measured against before you sign.

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