Quick answer
Mostly because the power itself got more expensive. Capacity prices in the MISO grid that serves Ameren Illinois jumped from about $30 to $666.50 per megawatt-day for summer 2025, lifting Ameren's supply price about 50%. Summer 2026 supply was 11.3¢ per kWh, and the price from October 2026 is 10.4¢, about 24% above a year earlier.
What changed on Ameren bills in 2025 and 2026?
| When | What changed | Effect on bills |
|---|---|---|
| June 2025 | MISO summer capacity price jumped from about $30 to $666.50 per megawatt-day | Supply price up about 50%, from roughly 8¢ to 12¢ per kWh |
| October 2025 | Supply price of 8.402¢/kWh for the first 800 kWh | Down more than 30% from summer |
| January 2026 | Delivery rate case decided | Ameren expected delivery rates to stay about the same |
| June 2026 | Summer supply price of 11.3¢/kWh | Nearly 40% higher than two summers earlier |
| October 2026–May 2027 | 10.4¢/kWh for the first 800 kWh, 8.3¢ above | About 24% higher than the October 2025 price |
For each period's price, see the Price to Compare tracker.
What is MISO, and why does it set my summer price?
MISO is the grid operator for central and southern Illinois. Each spring it holds a capacity auction that pays power plants to be available, with separate prices for each season. Summer carries most of the cost: the summer 2026 price was $424.30 per megawatt-day, down from $666.50 in 2025 but far above the fall, winter and spring prices.
Unlike PJM, which serves ComEd, MISO has no price cap, so Ameren's summer prices can swing more from year to year in either direction. Ameren itself says the overall cost of electricity remains at historically high levels.
What are the charges on my Ameren bill?
| Section | Line item | What it pays for |
|---|---|---|
| Supply | Purchased Electricity | The power itself, bought for you and passed through without markup |
| Supply | Transmission Service Charge | Moving power over high-voltage lines |
| Supply | Supply Cost Adjustment | Costs of buying power, such as working capital and uncollectible bills |
| Delivery | Customer Charge and Meter Charge | Fixed monthly fees for billing, service and your meter |
| Delivery | Distribution Delivery Charge | Local poles, wires and their upkeep, per kWh |
| Taxes and riders | Energy efficiency, renewable and clean energy charges | State-required programs, renewable and zero-carbon power |
| Taxes and riders | Electricity excise and municipal taxes | State and local taxes |
Ameren says supply is about half of a typical customer's bill. It's the part that rose most, and the part solar replaces for every kWh your panels produce and you use.
Why is Ameren's winter price lower above 800 kWh?
From October through May, Ameren charges less for every kWh over 800 in a month, on both supply and delivery. For October 2026–May 2027, supply is 10.4¢ for the first 800 kWh and 8.3¢ above. It mainly helps homes with electric heat. In summer, every kWh is billed at the higher summer price, which is why June through September bills climb fastest, along with air conditioning.
Will Ameren bills keep going up?
- Capacity: MISO prices set the summer supply price each June, and without a cap they can rise or fall sharply.
- Delivery: Ameren filed a 2028–2031 grid plan in January 2026; regulators are expected to rule by December 2026, with new rates from January 2028.
- State energy law: the 2026 Clean and Reliable Grid Affordability Act adds a small charge for grid batteries starting in 2030, and the Illinois Power Agency estimates the law lowers bills overall by 2031.
How can I lower my Ameren bill?
- Check supplier and aggregation deals. The Citizens Utility Board warns that alternative suppliers may charge even more than Ameren. Compare any offer with Ameren's Price to Compare.
- Power Smart Pricing: Ameren's hourly supply rate follows market prices, which are usually lowest at night. Ameren doesn't guarantee savings.
- Budget billing spreads your costs evenly over 12 months but doesn't lower the total.
- Help paying: LIHEAP and Ameren's assistance programs open each fall for households that qualify.
See hourly pricing with solar for how these rates work with panels.
How much would solar cut my Ameren bill?
| Monthly bill | System | Monthly savings, year one | Cost after incentives | Payback |
|---|---|---|---|---|
| $150 | 7.6 kW | $106 | $11,400 | 9 yrs |
| $250 | 13.2 kW | $184 | $19,600 | 8.9 yrs |
| $350 | 19.2 kW | $268 | $28,600 | 8.9 yrs |
Solar replaces the supply and per-kWh delivery charges on the power you use as it's produced, and earns a supply-rate credit on what you export. Fixed customer and meter charges stay. Downstate homes also get more sun than the Chicago area, which helps. Enter your bill in the solar savings calculator or see Ameren Illinois solar.
Sources
- Citizens Utility Board: Report on 2026 electric rates
- Citizens Utility Board: Ameren Illinois price for electricity has dropped 31 percent as of October 1 (2025)
- NPR Illinois: Regulators strike millions from Ameren, ComEd electric rate hike requests (December 2025)
- 25 News Now: Ameren Illinois electric rates set to rise beginning June 1 (May 2026)
- WSIU: CUB warns Ameren customers about alternative supplier deals (June 2026)
- WMBD: Ameren Illinois electricity price changes October 1 (2026)
- Ameren Illinois: Electric supply price change
- Plug In Illinois (Illinois Commerce Commission): Ameren Illinois Price to Compare
- Enel North America: MISO 2026–2027 capacity auction results
- Ameren Illinois: Bill terms and definitions
- Ameren Illinois: System upgrades and grid plan
- WTTW: Pritzker signs major energy reform bill (January 2026)
- Ameren Illinois: Power Smart Pricing
- Ameren Illinois: Budget Billing
This guide is general information, not tax, legal or financial advice. Incentive programs change, so confirm current terms with your installer, your utility and a tax professional.