AI Data Centers Push the Largest US Grid to Shortage Alerts
The largest US grid, PJM, added a capacity-shortage alert on 24 June 2026 as AI data-center demand outpaces supply; its 2027/2028 auction fell short by 6.6 GW.
AI Data Centers Push the Largest US Grid to Shortage Alerts
On 24 June 2026, PJM Interconnection, the largest US grid operator, added a new Capacity Advisory to warn when electricity supply is approaching a shortfall, even outside the extreme heat or cold that has historically driven shortages. The change took effect immediately. It lands as data-center demand outpaces new power supply across a grid serving 67 million people, and after PJM's latest capacity auction fell short of its own reliability requirement by about 6.6 GW.
- On 24 June 2026, PJM added a Capacity Advisory, effective immediately, to flag approaching shortfalls up to five days out, even in mild weather.
- PJM serves 67 million people across 13 states and DC, and now sees forecast capacity deficits outside extreme weather as demand outpaces new supply.
- Its 2027/2028 capacity auction fell short of the reliability requirement by about 6.6 GW, the first time the entire grid came up short.
- Capacity costs for 2027/2028 hit a record $16.4 billion; nearly 5,100 MW of the latest demand increase is attributed to data centers.
- A second new procedure lets PJM, under a federal order, require large loads to switch to backup generation within 15 minutes as a last resort.
What PJM changed
The new Capacity Advisory is a revision to PJM's Manual 13, endorsed by stakeholders at the 24 June Markets and Reliability Committee meeting and effective immediately. Issued up to five days ahead, like a Hot or Cold Weather Alert, it gives members advance notice when available generation is forecast to approach the demand requirement in a zone.
Items labeled projection are forecasts or stated plans, not built facts.
The reason for the new tool is the shift it describes. PJM capacity emergencies have historically tracked systemwide heat or cold alerts. The operator now reports forecast or actual capacity deficits outside those extreme periods, and expects such instances to increase as demand growth outpaces new power resources and intermittent generation makes up a larger share of the grid.
An advisory anticipates concrete steps: recalling or rescheduling generation and transmission maintenance outages, notifying neighboring grids to prepare for reduced imports from PJM, and asking members to update information on generator availability, fuel supply, and environmental constraints.
Why now: demand outrunning supply
The advisory follows a capacity auction that came up short. In the 2027/2028 Base Residual Auction, committed supply fell short of PJM's FERC-required reliability requirement by about 6,623 MW, the first time the entire grid cleared below the standard. PJM held a 14.8 percent reserve margin against a target of 20 percent.
The cost moved with it. Capacity procured for 2027/2028 cleared at a record $16.4 billion, and PJM attributed nearly 5,100 MW of the demand increase in that cycle to data centers. Retail bills are expected to rise between 1.5 percent and 5 percent for some PJM customers in the year starting June 2026 Projection.
The trajectory points up. PJM expects its summer peak load to grow about 3.6 percent a year to roughly 222 GW by 2036 Projection, with data centers the dominant driver. Bloomberg has reported PJM scenarios pointing to a supply shortfall of up to 60 GW over the next decade absent major new generation Projection.
The backup-generator backstop
PJM paired the advisory with a separate emergency procedure aimed squarely at large loads. When conditions are extreme, PJM may request a US Department of Energy order allowing data centers and other large users to run on-site backup generation as a last resort, to avoid outages for residential and other retail customers. The three new measures escalate in stages.
| Procedure | What it signals | What it requires |
|---|---|---|
| Capacity Advisory | Approaching shortfall, up to five days out, even in mild weather | Advance notice; recall maintenance outages, alert neighbors and members |
| Backup Generator Warning | Extreme conditions; coordination begins among PJM and utilities | Determine how much load can shift to backup generation per zone |
| Backup Generator Action | Last resort, before voltage reduction or manual load shedding | Large loads ready to move to backup generation within 15 minutes |
A dispute over the forecasts
How much of this is data centers is contested inside PJM itself. The grid's independent market monitor named forecast data-center load growth as the primary cause of the strain so far, while casting doubt on the demand numbers feeding PJM's own planning models.
"The accuracy of those forecasts is highly questionable."
PJM independent market monitor
PJM's own filings point to more than one cause: generator retirements, interconnection backlogs, permitting delays, supply-chain constraints, and compressed auction schedules alongside the load surge. The open question is whether data-center growth merely exposed those weaknesses or fundamentally changed the supply-and-demand balance. The answer shapes how much new generation, and how much ratepayer cost, the buildout ultimately requires.
What comes next
The advisory is one piece of a wider response. In January, PJM's board moved to launch a reliability backstop procurement to secure more supply, plus a fast-track interconnection path for large loads that bring their own generation, with large load defined as at or above 50 MW. The next capacity auction, for the 2028/2029 delivery year, is set to begin around 30 June 2026 Projection.
The politics are escalating in parallel. The Trump administration has pushed PJM to hold an emergency reliability auction in which data-center operators would bid on long-term contracts to fund new generation, a plan reported to be worth more than $15 billion Projection. For now, the new alerts are an admission in plain terms: on the largest US grid, the AI buildout is arriving faster than the power to run it.
Grid forecasts, auction results, and the rules behind them change as new filings land. Verify current figures with PJM and FERC before relying on any number here.
Sources
- PJM Interconnection, Manual 13 emergency-procedure revisions (Capacity Advisory; Emergency Use of Backup Generators), endorsed at the Markets and Reliability Committee, 24 June 2026.
- PJM Board of Managers, letter on the Critical Issue Fast Path for Large Load Additions, 16 January 2026.
- PJM Interconnection, "PJM Board Outlines Plans To Integrate Large Loads Reliably", 16 January 2026.
- American Public Power Association, "PJM Adds Emergency Procedures to Maintain Reliability", 25 June 2026.
- Bloomberg, "AI Data Center Growth Prompts New Capacity Advisory for US Largest Power Grid", 24 June 2026.
- Data Center Knowledge, "PJM Monitor: AI Data Center Growth Reshaping Power Markets", June 2026.
- Utility Dive, "PJM trims near-term load forecast on stricter data center vetting, economic outlook", 15 January 2026.
- DatacenterDynamics, "PJM facing up to 60GW power shortfall over next decade, report", June 2026.
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