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Why Your Ameren Bill Keeps Going Up (and What MISO Has to Do With It)

Ryan Cook•March 30, 2026•Updated Sep 13, 2026

If you're an Ameren Illinois customer and you've been staring at your summer bills wondering what happened — you're not imagining it. Your bill went up somewhere between 18% and 22% in summer 2025. That's $38 to $46 extra per month that didn't exist the year before.

Updated September 13, 2026: the summer 2026 Price to Compare is 11.326¢/kWh for the first 800 kWh, effective June 1 through September 30, 2026, per the ICC's Plug In Illinois page.

Most people blame Ameren. And Ameren is partly responsible — they've been filing rate increase after rate increase with the ICC. But the biggest hit came from somewhere most customers have never heard of: MISO.

What Is MISO and Why Should You Care?

MISO — the Midcontinent Independent System Operator — runs the power grid for central and southern Illinois. Ameren doesn't generate its own electricity. It buys it through MISO's markets, and those costs get passed directly to you.

Every year, MISO holds a capacity auction. Utilities bid to secure enough power to keep the lights on during peak demand. In 2024, that auction cleared at $30 per megawatt-day. A reasonable number. The grid was stable.

In 2025, it cleared at $666.50 per megawatt-day.

That's a 22x increase in a single year. And every dollar of it landed on your bill starting June 1st.

Why Did the Price Jump 22x?

Two things collided.

Coal plants are shutting down faster than replacements are coming online. MISO's reserve margin — the cushion between how much power is available and how much people need — dropped from 6.5 gigawatts to 2.6 gigawatts in two years. That's not a comfortable cushion. That's a region running on fumes during a heat wave.

Data center demand is eating up what's left. I wrote about this in detail in my data centers post, but the short version: facilities that consume as much power as mid-size cities are being built across Illinois, and they're competing for the same limited supply your house runs on.

When supply is tight and demand is surging, auction prices explode. That's what happened.

The Delivery Side Is Getting Hit Too

The capacity auction is the supply cost. But your bill has two sides — supply and delivery.

Ameren has been filing delivery rate cases with the Illinois Commerce Commission almost continuously. The ICC granted a $48 million increase for electric delivery charges in late 2025 — less than Ameren asked for, but still a meaningful hit.

And an Ameren representative told regulators the company intends to file another rate increase request in 2026, regardless of what they were granted in the current case. That's not speculation — that's what they told the ICC on the record.

So supply costs are spiking from MISO auctions, and delivery costs are climbing from Ameren's own infrastructure spending. Both sides of your bill are going up, driven by different forces, with no mechanism to bring either one down.

What Does This Mean Going Forward?

The Citizens Utility Board projects continued increases for Ameren customers. Historically, Ameren rates have inflated about 6% per year on average. That compounds. A $170 bill today becomes $195 next year. $225 the year after. $305 by 2032 if the pattern holds.

There's some seasonal relief — Ameren's supply rate dropped to 8.4 cents/kWh for the October-May winter period. But that dip disappears every June when summer capacity pricing kicks back in. The pattern is a ratchet: summer spikes get worse, winter lows barely improve, and the annual average keeps climbing.

What's Actually in Your Control

I've been having this conversation with homeowners across Ameren territory — Belleville, Springfield, Decatur, Champaign, Edwardsville — and the reaction is always the same. Nobody likes hearing this. But they'd rather know.

A solar lease gives you a rate as low as $0.10/kWh, predictable for 25 years. Ameren's all-in rate is already over 50% higher than that, and it's going in one direction. The gap between what you'd pay on solar and what you'd pay on the grid gets wider every single year.

For homeowners who qualify, Solar for All covers the entire cost — I had a customer in Belleville whose average bill went from $245/month down to $65/month with a system that cost them nothing.

If you're in Ameren territory, your bill is going to keep doing what it's been doing. The only question is whether you're going to keep paying it or fix it. Run your numbers on our savings calculator or call me at (618) 217-2001.

Sources

Frequently Asked Questions

Ameren Illinois bills keep going up because of two compounding forces: MISO capacity auction clearing prices spiked 22x in a single year (from $30 to $666.50 per megawatt-day in 2025-2026), and the Illinois Commerce Commission has approved a series of delivery rate increases totaling $48 million in late 2025 alone. The MISO auction spike flows directly into the supply portion of your bill since June 1, 2026, while the delivery rate increases cover Ameren's infrastructure spending and appear on the delivery portion. Both components are rising simultaneously with no mechanism to bring either down. Ameren has told Illinois regulators it intends to file another rate increase request in 2026 regardless of the current case. The underlying drivers — coal plant retirements, tight MISO reserve margins (dropped from 6.5 gigawatts to 2.6 gigawatts in two years), and data center demand — are structural, not temporary.

MISO — the Midcontinent Independent System Operator — is the regional grid operator for central and southern Illinois, including all Ameren Illinois territory. Ameren does not generate its own electricity; instead, it procures power through MISO's wholesale markets, and those costs pass directly through to residential bills. Every year MISO holds a capacity auction in which utilities bid to secure enough power for peak demand — the clearing price for summer 2025-2026 hit $666.50 per megawatt-day, a 22x increase over the prior year's $30. That $636.50 per megawatt-day jump translates into cents per kilowatt-hour on your summer bill, which is why Ameren Illinois residential rates jumped 18-22% for the summer 2025 season and why the summer 2026 Price to Compare reset to 11.326¢/kWh (June 1 through September 30, 2026). MISO's reserve margin has also tightened significantly, from 6.5 gigawatts to 2.6 gigawatts in two years, indicating a grid with shrinking headroom.

Ameren Illinois residential bills rose approximately 18-22% for summer 2025 compared to summer 2024, translating to about $38 to $46 per month of extra cost for a typical household. The primary driver was the MISO capacity auction clearing price jumping from $30 per megawatt-day to $666.50 per megawatt-day in a single year — a 22x increase that flowed directly into the supply portion of Ameren bills starting June 2025. Over the longer time horizon, Ameren Illinois residential rates have risen approximately 94% since 2021, making Illinois one of the fastest-rising electricity markets in the Midwest. Current all-in Ameren rates average 15.5¢/kWh, with summer rates reaching approximately 20¢/kWh during peak months. The Illinois Commerce Commission approved a $48 million delivery rate increase for Ameren in late 2025, with another Ameren rate request already telegraphed to regulators for filing in 2026.

Yes — Ameren Illinois rates are projected to keep rising through at least 2026 and 2027, based on both Ameren's stated filings and independent Citizens Utility Board projections. Historically, Ameren Illinois residential rates have risen approximately 6% per year on average, a compounding pattern that produces meaningful long-term increases: a $170 monthly bill today becomes approximately $195 next year, $225 the year after, and roughly $305 by 2032 if the pattern continues. Ameren has already told the Illinois Commerce Commission it plans to file another rate increase request in 2026 regardless of outcomes in the current delivery case. The MISO capacity auction spike to $666.50 per megawatt-day is already locked into the 2026 summer supply rate, and coal plant retirements combined with tightening reserve margins suggest further upward pressure on future capacity auctions. CUB describes the trajectory as elevated rates for at least the next few years.

The MISO capacity auction clearing price jumped from $30 per megawatt-day in 2024 to $666.50 per megawatt-day for the 2025-2026 summer season — a 22x increase that flowed directly into Ameren Illinois residential bills starting June 2025. Capacity charges are a fixed component of your supply rate that covers Ameren's obligation to reserve grid capacity for peak demand events; when MISO's auction clears at a higher price, utilities pass that cost through to customers with essentially no buffer. For a typical Ameren household using 1,000 kWh per month, the 22x capacity price jump added approximately $38 to $46 per month to summer bills, or roughly $300-400 per summer season. The drivers behind the price jump were coal plant retirements outpacing new generation coming online, MISO's reserve margin collapsing from 6.5 gigawatts to 2.6 gigawatts, and data center demand consuming available capacity. Those drivers are structural, not temporary.

The most effective way to structurally reduce an Ameren Illinois electric bill is to shift a significant portion of your electricity consumption onto solar, which gives you a predictable rate that doesn't move with MISO capacity auctions or delivery rate cases. A $0-down solar lease in Ameren territory can run as low as $0.10 per kilowatt-hour for 25 years — roughly 35% below the current Ameren all-in rate of 15.5¢/kWh and far below summer peak rates near 20¢/kWh. Income-qualified households can access Solar for All (ILSFA) at $0 total cost with guaranteed bill savings. For near-term relief without solar: shift heavy loads (laundry, dishwasher) to off-peak hours, check eligibility for LIHEAP assistance, request a CUB bill review to catch billing errors, and consider supply-side shopping with an alternative retail electric supplier (results vary). But the durable fix is decoupling from the utility rate curve.

Ameren Illinois applies a seasonal rate structure where summer delivery charges are substantially higher than winter — not a formal surcharge but an embedded seasonal escalation. Non-summer (October through May) delivery rates are approximately 4.572¢/kWh, jumping to approximately 7.811¢/kWh during summer months (June through September) — a 71% increase in delivery alone. On top of that, summer capacity pricing flows through from MISO auctions: the 2025-2026 summer capacity price of $666.50 per megawatt-day (vs. $30 the prior year) added approximately $38-46 per month to summer bills. The combined effect pushes Ameren Illinois all-in rates from approximately 15.5¢/kWh non-summer to roughly 20¢/kWh during summer peak, with hottest days reaching 22-23¢/kWh. This seasonal pattern is one reason solar leases (predictable year-round at a rate as low as $0.10/kWh) deliver particularly large summer-month savings for Ameren Illinois customers.