Quick answer
Partly, yes. PJM's independent market monitor attributed about $29.4 billion, or 46%, of capacity costs in the last four grid auctions to data center demand, and those costs flow into ComEd's supply price. The Citizens Utility Board says the 2026 ComEd price spike is largely the result of new and proposed data centers. Illinois lawmakers may take up data center rules in the November veto session.
How do data centers affect my electric bill?
Through capacity costs. PJM, the grid operator for ComEd's area, holds auctions that pay power plants to be available during peak demand. When forecast demand jumps, as it has with planned data centers, prices rise, and ComEd passes those costs through in its supply price. The Citizens Utility Board says capacity makes up about 20% of ComEd's supply price.
| Delivery year | Price per megawatt-day | Data centers' share of costs (market monitor) |
|---|---|---|
| 2024/25 | $28.92 | Before the spike |
| 2025/26 | $269.92 | About half of the $30.8 billion across 2025/26 and 2026/27 combined |
| 2026/27 | $329.17 (price cap) | Included above |
| 2027/28 | $333.44 (price cap) | About $6.5 billion, roughly 40% |
| 2028/29 | $325 (price cap) | About $6.3 billion, or 38% |
PJM said the 2028/29 auction would have cleared at about $777 per megawatt-day in the ComEd zone without the price cap. See why ComEd bills are so high.
How much have capacity costs added to ComEd bills?
ComEd estimated that the June 2025 auction added about $10.60 a month to the average residential bill, and that bills from June 2026 through May 2027 would run about 12% higher on average. ComEd's summer 2026 supply price was 10.399¢ per kWh, about 50% higher than two years earlier, according to the Citizens Utility Board. See the Price to Compare tracker for the current rate.
How many data centers want to connect in Illinois?
A lot. When the Illinois Commerce Commission approved new rules for very large customers in March 2026, ComEd had more than 75 large-load projects expected to draw over 28,000 megawatts, more than its highest-ever peak of about 24,000 megawatts. A ComEd official said that if every project came in at full demand, it would more than double the system's peak by roughly 2040. Ameren reported 850 megawatts of data center construction agreements in Illinois in early 2026, with several gigawatts more under study.
Not every project will be built, but the forecasts alone move the capacity auctions.
What is Illinois doing about data center costs?
- Large-load rules: the ICC's March 2026 order requires new customers of 50 megawatts or more to post deposits, starting at $1 million for 50 to 200 megawatts, so households aren't left with stranded costs.
- Tax incentive pause: Governor Pritzker directed the state to stop signing new data center tax incentive agreements starting July 1, 2026; existing deals are honored.
- The POWER Act: a proposal for new data centers to bring and pay for their own clean power and grid upgrades stalled in the spring session. Sponsors said it could come back in the fall veto session, which runs November 17 to 19 and December 1 to 3, 2026, and the governor asked lawmakers to revisit data centers then.
We'll update this guide as the legislature acts.
Are Ameren bills affected too?
Ameren Illinois is in a different grid, MISO, with its own auction. MISO's summer capacity price jumped to $666.50 per megawatt-day for 2025/26, then eased to $424.30 for 2026/27, which MISO credited to more supply. Ameren has data center projects too, but we haven't found MISO tying its prices to them. See why Ameren bills are so high.
How can homeowners protect themselves from rising electricity costs?
- Make your own power. Solar replaces the supply and delivery charges on every kWh you use as it's produced, so capacity-driven price increases matter less. See is solar worth it in Illinois?
- Add a battery. It shifts your solar to the evening, keeps power on in outages and earns the storage rebate through the utility's virtual power plant. See what a home battery costs.
- Watch your rate plan. Hourly or time-of-day pricing can help if you can shift use away from peak hours. See ComEd Hourly Pricing with solar.
Try the solar savings calculator with your current bill to see what solar would save at today's prices.
Sources
- Citizens Utility Board: PJM capacity auction leads to price spike for second straight year (July 2025)
- Citizens Utility Board: Why is ComEd's price spiking? (June 2026)
- Utility Dive: Data centers drove PJM capacity costs, market monitor says
- PJM: 2027/2028 Base Residual Auction report
- Utility Dive: Data centers and the 2027/28 PJM capacity auction
- Utility Dive: PJM capacity auction clears at price cap again (July 2026)
- ComEd: Why is your electric bill going up?
- NPR Illinois: Regulators approve ComEd plan for large data center customers (March 2026)
- NPR Illinois: Energy demand in ComEd territory could double by 2040 (April 2026)
- Nasdaq: Ameren Q1 2026 earnings call highlights
- NRDC: Pritzker announces two-year suspension of data center tax incentives (June 2026)
- Capitol News Illinois: POWER Act data center regulation won't move forward this spring (May 2026)
- Illinois General Assembly: 2026 Senate veto session calendar
- Citizens Utility Board: Why is Ameren's electricity price spiking? (May 2025)
- Enel North America: MISO 2026–2027 capacity auction results
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.