What capacity markets actually do
Electricity demand peaks for a few hours each summer. Those peaks determine how much generation capacity the grid needs to keep on hand — including reserves for outages and weather extremes. Generators committing to be available during those peaks need to be compensated, separately from the energy they actually sell during normal hours.
That's what capacity markets pay for. Three years before each delivery year, generators (and large flexible loads) submit offers to be available. The auction clears at a price that procures enough capacity to meet a reserve margin requirement. Generators who clear are paid a monthly "capacity payment" for the next year, whether they produce energy or not.
That payment shows up on your bill as a passthrough — usually a $/kW-month charge based on your "capacity tag," a number derived from your historical peak-hour consumption.
Which markets have them
Not all deregulated markets use capacity markets. The structure varies meaningfully:
| Market | Capacity Market | How Your Tag Is Set |
|---|---|---|
| PJM | Yes — annual Base Residual Auction (BRA) | Average load during the 5 highest summer peak hours (5CP), measured the prior year |
| NYISO | Yes — monthly ICAP auctions | Coincident peak load measured during one peak hour per month |
| ISO-NE | Yes — Forward Capacity Auction (FCA) | Installed Capacity Requirement (ICR) sized to annual peak |
| ERCOT | No (energy-only design) | 4CP — average load during 4 highest summer peak hours sets transmission charges |
| MISO | Limited (Planning Resource Auction) | Coincident peak demand during seasonal peak hours |
| CAISO | Resource Adequacy program (bilateral, not auction) | Monthly peak load forecasts; charges flow through retail supply |
Even ERCOT, which has no capacity market, uses peak-hour consumption (the 4CP) to set transmission charges — meaning the same operational discipline that controls capacity tags in PJM controls transmission costs in Texas.
Why capacity prices spiked
For most of the 2010s, capacity prices were relatively stable — sometimes oversupplied, with low clearing prices. That changed sharply starting around 2022. Several structural factors compounded:
Generator retirements outpacing new builds
Coal plants kept retiring on schedule. Older gas plants started retiring early as economics shifted. New solar and wind got built but provide capacity differently than thermal generation — and battery storage, while growing, hasn't filled the gap fast enough.
Interconnection queue backlogs
New generation projects are stuck in interconnection queues for 4-5 years or more in most markets. PJM's queue had over 200 GW of pending projects as of late 2024. The pipeline exists; the deliveries don't.
Demand growth from data centers and electrification
Hyperscale data center growth, especially in PJM's Virginia load zone, drove unprecedented demand forecasts. Electrification of transportation and buildings adds incremental load year over year. Demand is growing for the first time in over a decade.
Capacity market rule changes
FERC-approved rule changes — including PJM's capacity performance reform and reserve margin recalibrations — tightened the required quantity of capacity. Same available supply, higher required quantity, higher price.
$329.17/MW-day
PJM's July 2024 capacity auction clearing price — at the market price cap, up 22% from the prior year
How capacity shows up on your bill
The naming varies by supplier and utility, but capacity charges typically appear as one or more of these line items:
- Capacity or ICAP — the most direct labeling
- PJM Capacity Passthrough — pass-through from the supplier
- NITS (Network Integration Transmission Service) — transmission related, sometimes bundled with capacity
- RPM Charge (Reliability Pricing Model) — PJM's specific naming
- Sometimes bundled into a generic "transmission and capacity" line, especially on consolidated invoices
The unit is usually $/kW-month based on your capacity tag. If your tag is 500 kW and the rate is $20/kW-month, your monthly capacity charge is $10,000 — $120,000 per year, before any other components.
For a manufacturing facility or data center with a 5 MW capacity tag at current PJM rates, capacity alone can run over $1M annually — sometimes more than the energy line itself.
What buyers can actually do
The capacity charge isn't something you absorb passively. Three categories of action change the bill:
Capacity tag management
Reducing load during the specific peak hours that set your tag for the next year. In PJM, that's the 5 highest summer afternoon peaks. The challenge is forecasting which days and hours those will be — heat events, weekday vs weekend patterns, regional load forecasts. With reliable forecasting and operational coordination, capacity tags can drop 15-25% year over year.
Demand response enrollment
Programs that pay you to reduce load when the grid signals an emergency. Revenue varies by market, but for industrial facilities with operational flexibility, DR can offset 30-50% of capacity charges. Worth running the analysis even for facilities that think they can't reduce load — partial reductions sometimes qualify.
Procurement strategy
How capacity is passed through in your supplier contract matters. Some suppliers pass through at cost (clean and verifiable); others mark up; others bundle it into a fixed all-in rate that hides the capacity component. Knowing what you're signing changes both negotiation leverage and budget predictability.
Bottom Line
Capacity is the largest cost on most C&I energy bills that isn't being actively managed. The 4-5 hours each summer that set your tag determine the next year's charge. Forecasting those hours, managing load during them, and structuring your supplier contract to keep capacity transparent are the three levers that matter. None of them require capital investment — just discipline and a good forecast.
