Illinois Capacity Charges Just Took Another Step Up: Why Cutting Consumption Didn't Lower Your ComEd Bill
Capacity costs on ComEd bills rose again in June 2026, and they are billed against a kilowatt capacity obligation, not kilowatt-hours. Most facilities never isolated the charge that caused the increase.
The PJM capacity auction for the 2026/2027 delivery year (June 1, 2026 through May 31, 2027) cleared at $329.17 per megawatt-day in the ComEd zone. That is about 22% above the $269.92 price for 2025/2026, and about 1,038% above the $28.92 price for 2024/2025.
Converted to the monthly unit used for billing, that is roughly $10.01 per kW-month of capacity obligation, up from about $8.21 a year earlier and about $0.88 two years earlier. Each utility then applies its own scaling adjustments to individual accounts.
The step up is not temporary. The next two auctions also cleared at the price cap: $333.44 per megawatt-day for 2027/2028 and $325.00 for 2028/2029. Elevated capacity pricing is already set through May 2029.
View the chart data
| Delivery year | Period | Clearing price ($/MW-day) | Status |
|---|---|---|---|
| 2024/2025 | June 2024 to May 2025 | $28.92 | Past |
| 2025/2026 | June 2025 to May 2026 | $269.92 | Past |
| 2026/2027 | June 2026 to May 2027 | $329.17 | On bills now; cleared at the price cap |
| 2027/2028 | June 2027 to May 2028 | $333.44 | Already set; cleared at the price cap |
| 2028/2029 | June 2028 to May 2029 | $325.00 | Already set; cleared at the price cap |
The result is a cost increase that many Illinois industrial, manufacturing, chemical, and logistics facilities absorbed without understanding the billing determinant behind it.
Reducing total consumption is not the same as reducing capacity exposure. A facility can use fewer kilowatt-hours and still carry a similar capacity obligation if it does not reduce its load during the summer peak hours that set that obligation.
That distinction is now central to Illinois electricity cost management.
The capacity cost increased by about 22%, but the unit of measure matters more
Capacity is billed against a kilowatt capacity obligation, not against kilowatt-hours. That difference changes the financial analysis.
- Kilowatt-hours, or kWh, measure consumption.
- Kilowatts, or kW, measure demand.
- Capacity charges are based on the obligation to have power available during high-demand conditions.
PJM prices capacity per megawatt-day. To compare it with a monthly bill, multiply by 365, divide by 12, and divide by 1,000. On that basis, a facility with a 1,000 kW capacity obligation would see the following approximate impact:
- 2025/2026 (about $8.21 per kW-month): $8,210 per month
- 2026/2027 (about $10.01 per kW-month): $10,012 per month
- Monthly increase: about $1,802
- Annualized increase: about $21,626
A facility with a 5,000 kW capacity obligation would see an annualized increase of about $108,131, before any other changes in supply, delivery, transmission, riders, and assessments.
These examples are directional. The actual bill applies the utility's scaling factor and PJM's forecast pool requirement to the account's peak load contribution, and supply contracts may add their own terms. But the financial logic remains the same:
The charge scales with the facility's capacity obligation, not simply with the amount of electricity consumed.
How the charge appears depends on the supply arrangement. ComEd customers with peak demand of 100 kW or more take supply either from a retail electric supplier or from ComEd's hourly-priced default service. Depending on that arrangement, capacity may appear as its own line item, be embedded in the supply price, or be passed through under the supplier contract.
ComEd states that capacity charges are passed through without markup and are included in every customer's bill, either as a separate line or within the supply charge. The ComEd capacity charge explanation provides background on the distinction between supply and delivery costs.
The billing treatment differs. The exposure is still real.
How the capacity obligation is set, and when it resets
Each ComEd account carries a peak load contribution, or PLC. It is based on the account's load during system peak periods on hot afternoons the prior summer, not on the account's total usage or its own highest demand of the year.
The PLC is adjusted by a utility scaling factor and PJM's forecast pool requirement to produce the capacity obligation. That obligation resets every June 1 and applies for the full 12-month delivery year.
The timing matters:
View the chart data
| Summer peak hours | Obligation billed | Clearing price ($/MW-day) |
|---|---|---|
| Summer 2025 | June 2026 to May 2027 | $329.17 |
| Summer 2026 | June 2027 to May 2028 | $333.44 |
| Summer 2027 | June 2028 to May 2029 | $325.00 |
Summer 2026 is already locked in for the obligation billed from June 2027. The next decision point that a facility can influence is its load during the summer 2027 peak hours.
Why Illinois electricity costs moved: PJM, data centers, and a visible political fight
ComEd serves northern Illinois within the PJM Interconnection market. PJM operates the capacity market that procures future generation resources to maintain reliability during periods of high demand.
The auction price increased because the market is repricing the cost of reliable capacity. Rapid load growth, driven largely by data centers, is a major factor, while new generation has been slow to come online.
The Chicago area's concentration of data centers has made Illinois one of the most visible examples of the issue. Artificial intelligence workloads and data center expansion require large, continuous amounts of electricity. That load changes regional forecasts and increases competition for available capacity.
The impact is not limited to data centers. Industrial facilities, manufacturers, warehouses, and other large commercial customers are also exposed to the resulting PJM pricing structure.
The political reaction is now active. On September 23, 2026, Chicago Mayor Brandon Johnson and three aldermen introduced an ordinance proposing a 12-month moratorium on new data centers and material expansions of existing ones. The proposal still needs City Council approval. Several other Illinois municipalities have already paused new data center development, and Governor Pritzker paused new applications for state data center incentives.
These moves reflect a broader question: who should pay for the grid expansion required by rapidly growing loads?
Customers cannot resolve that policy question through procurement alone. They can, however, determine whether their own billing, contracts, demand profile, and capacity assignments are correct.
Why cutting consumption alone did not lower your ComEd bill
This is the most important point for an Illinois facility manager.
A reduction in kWh consumption does not automatically reduce a capacity charge.
Capacity exposure traces back to the account's load during the prior summer's peak periods and the capacity obligation assigned to it. A facility may reduce annual production, shut down equipment, or improve overall efficiency and still see little relief if its load during those peak hours stays the same.
Consider two illustrative facilities:
- Facility A reduces annual consumption by 12% but continues to run its largest electrical loads on hot summer afternoons.
- Facility B reduces annual consumption by only 5% but actively manages its load during the summer peak hours.
Facility B may achieve a more meaningful reduction in future capacity exposure.
This does not mean consumption reduction is unimportant. Lower consumption reduces energy supply costs and may reduce other usage-based charges. It means consumption reduction is not a substitute for peak-demand management.
The relevant questions include:
- What capacity obligation was assigned to the account?
- Which historical interval data established the obligation?
- What was the facility's load during the summer peak hours that set it?
- Were the account's meters, multipliers, and billing determinants applied correctly?
- Is capacity being passed through under the supply contract?
- Does the contract fix the capacity price, or only the energy commodity price?
A fixed-rate contract does not automatically eliminate capacity risk. Some contracts include capacity in a fixed price. Others pass capacity through as a variable charge. The contract language must be reviewed alongside the bills and interval data.
This is why a utility bill audit should be the first step.
Start with a utility audit before changing operations or contracts
It is nearly impossible to fix what you do not understand.
An Illinois utility audit creates the verified baseline needed to separate unavoidable market costs from errors, misapplications, and controllable exposure. It should examine the following:
Rate classification verification
Confirm that each facility is on the correct rate class for its operations, voltage level, service characteristics, and demand profile. A misclassification can affect delivery charges, demand treatment, riders, and eligibility for applicable programs.
Capacity pass-through review
Determine whether the electricity contract includes capacity in the fixed price or passes it through to the customer. Review the definition of capacity, the applicable PJM zone, the pricing formula, and the supplier's right to adjust the charge.
Demand ratchet analysis
Some commercial and industrial tariffs use demand ratchets or historical demand provisions. These can cause a facility to pay based on prior peak demand even after current usage declines. The tariff language and account history must be tested together.
Peak load contribution and capacity obligation review
Review the assigned capacity obligation and the interval data used to establish it. A facility should know whether the obligation reflects actual operations, estimated data, incorrect account association, or an avoidable peak event.
Meter multiplier and billing determinant validation
Verify meter multipliers, demand readings, service dates, account consolidations, and other determinants that feed the invoice. A small data error multiplied across several accounts can create a recurring overcharge.
Interval data validation
Monthly bills do not show enough detail to explain every demand outcome. Review interval data to identify when peaks occurred, which equipment was operating, and whether operational changes could reduce future exposure.
The audit should also review utility billing errors, tariff riders, transmission charges, corporate classification, and assessments. These items will not remove the PJM capacity increase, but they can reduce the total financial impact.
Discovery Energy conducts contingency-based utility bill audits across complex, multi-site portfolios. There is no upfront audit fee. Under the agreed terms, Discovery Energy is paid when the client receives qualifying refunds, credits or realized savings.
Five practical actions for Illinois facilities
Once the billing position is verified, facilities can make a more targeted energy procurement and industrial energy management decision.
Manage load during summer peak hours, not only total consumption
Use interval data to identify the operating conditions that drive load on hot summer afternoons. Evaluate load sequencing, nonessential equipment scheduling, thermal storage, battery storage, demand response, and process changes before summer 2027.
Do not assume that a broad efficiency project will reduce capacity exposure unless it changes load during those peak hours.
Review contract language before renewing
Identify whether the contract is:
- Fully fixed, including capacity and transmission
- Fixed for energy only, with capacity passed through
- Indexed to a market price
- Structured with a capacity adder
- Subject to repricing at a renewal or anniversary date
A contract that appears fixed on the summary page may still contain pass-through provisions in the supply agreement. With capacity prices already set through May 2029, check how each contract treats the 2027/2028 and 2028/2029 delivery years.
Use clear Buy, Wait, or Hedge guidance
Do not make a procurement decision based only on the current all-in rate.
- Buy when budget certainty is the priority and the forward market supports an acceptable risk-adjusted price.
- Wait when the contract allows flexibility, market conditions favor monitoring, and the facility can tolerate volatility.
- Hedge when partial protection is appropriate and the organization wants to limit exposure without locking the entire position at once.
Discovery's energy procurement process uses competitive RFPs, apples-to-apples bid comparisons, market timing, and contract tracking across deregulated markets.
Benchmark comparable Illinois facilities
Compare facilities by load profile, production schedule, demand intensity, capacity obligation, utility territory, and rate structure. A simple cost-per-kWh comparison may conceal a significant capacity or demand difference.
The right benchmark answers a more useful question: Why does one comparable facility carry a higher cost per unit of output, peak kW, or operating hour?
Create one integrated view of bills, contracts, and interval data
Capacity cannot be managed effectively when billing, procurement, and operations use separate datasets.
Discovery's TaraBase reporting platform consolidates bills, usage, contracts, savings, energy metrics, and ESG metrics into a single view. The goal is to connect:
- The bill to the account
- The account to the meter
- The meter to interval usage
- The usage to the capacity obligation
- The obligation to the supply contract
- The contract to the renewal and risk strategy
Sources
- PJM, 2028/2029 Base Residual Auction results (July 2026)
- NJBPU, An Investigation of PJM's Capacity Market (August 2026; clearing price history 2024/2025 through 2028/2029)
- ComEd, Capacity Charge Updates
- Exelon, ComEd mid-sized customer group declared competitive (October 2007)
- City of Chicago, Data Center Moratorium Ordinance (September 2026)
- Axios Chicago, Chicago mayor proposes 12-month moratorium on new data centers (September 2026)