PJM's Summer Stress Test: Why Dominion Sits at the Center of Grid Reliability Issues

PJM issued a Hot Weather Alert for the Mid-Atlantic and Dominion zones today. Temperatures approaching 90°F. Expected loads of 109,000 to 114,000 MW.

In April!

Hot Weather Alerts in shoulder months are uncommon. Specifically, they signal that PJM wants generators to update unit start-up lead times, defer maintenance, and prepare for conditions that, historically, belong to late June. The fact that this is happening in mid-April, for the second time this spring, says more about the summer ahead than any seasonal forecast.

Here is what we know, what the data shows, and what it means for organizations operating in PJM this summer.

Last Summer Rewrote PJM's Risk

On June 24, 2025, PJM recorded a preliminary peak load of 162,401 MW between 5 and 6 p.m. Eastern. That figure represents the third-highest peak in the grid operator's history. The day before, June 23, hit 161,770 MW, the fourth-highest ever. Both surpassed PJM's own pre-summer forecast of 154,000 MW by a significant margin.

Before this event, every entry in PJM's top-10 summer peaks dated to 2013 or earlier.

The all-time record remains 165,563 MW, set in 2006. Last June came within 3,162 MW of matching it. The temperature-humidity index reached 84 across PJM's footprint on multiple days. PJM has recorded a THI (Temperature Humidity Index) of 85 only twice in its history.

Generator performance during the heat wave exposed a specific vulnerability. Forced outages ran approximately 5 GW higher than PJM anticipated in its summer outlook. That gap, between what PJM expected to have available and what actually showed up, compressed reserve margins to their lowest levels in over a decade. PJM deployed demand response RTO-wide on June 24, reducing load by more than 4,000 MW during the worst hours. In total, PJM initiated six load management events across the summer.

Dominion: Where Data Center Growth Meets Physical Grid Constraints

The Dominion Energy service territory in Northern Virginia has become the single most consequential load pocket in PJM. Based on our demand analysis what traders and grid planners have been tracking for years: off-peak load in the DOM zone has risen by more than 4 GW over the past six years, driven almost entirely by data center expansion. Dominion exceeded its all-time record load multiple times in 2025 alone, setting new peaks in both winter and summer.

PJM's capacity market already reflects this concentration of risk. In the 2025/2026 Base Residual Auction (results published July 2024), the Dominion zone cleared at $444.26/MW-day, while the rest of PJM cleared at $269.92/MW-day. PJM attributed the premium directly to insufficient resources inside the region and binding transmission constraints that limit the ability to import capacity from adjacent zones.

The transmission system serving Northern Virginia is under acute stress. PJM's planning studies have identified heavy power flows toward key substations in Loudoun County, with the grid operator approving a $4.8 billion slice of transmission investment directed specifically at Dominion's territory. That figure sits inside a broader $11.8 billion system-wide transmission expansion plan approved in early 2026, the largest in PJM's history.

Six new transmission lines are being routed through the region, including high-voltage projects designed to relieve congestion around the data center corridor. The scale of that investment reflects a straightforward engineering reality: the wires serving Northern Virginia were not built for the load profile that data centers have created. Upgrading them takes years.

Three Consecutive Record Capacity Auctions

PJM's capacity market has sent an increasingly urgent signal over the past two years. The progression tells an interesting story.

For the 2024/2025 delivery year, PJM capacity cleared at $28.92/MW-day, with total procurement costs around $2.2 billion. For the 2025/2026 delivery year (auction held July 2024), the clearing price jumped to $269.92/MW-day for the RTO, with the Dominion and BGE zones clearing even higher. Total cost: approximately $14.7 billion.

The 2026/2027 auction (held July 2025) hit the FERC-approved price cap of $329.17/MW-day across the entire footprint. Total cost: $16.1 billion. No constrained zones. The whole RTO was tight.

Then came December 2025. The 2027/2028 Base Residual Auction cleared at $333.44/MW-day, again hitting the FERC cap across the entire PJM region. But this auction produced an outcome that no prior BRA had: PJM fell short of its reliability target.

Total procured capacity, including Fixed Resource Requirement commitments, reached 145,777 MW of unforced capacity. That number is 6,623 MW below PJM's 20% installed reserve margin target, the threshold designed to ensure no more than one unexpected loss-of-load event per decade. The cleared reserve margin came in at 14.8%. PJM's target is 20%.

This was the first time in the history of PJM's capacity market that the auction, including FRR, failed to meet the established reliability requirement.

The shortfall is attributable to a single driver. PJM's forecasted peak load for the 2027/2028 delivery year increased by approximately 5,250 MW over the prior year. Nearly 5,100 MW of that increase came from data center demand. On the supply side, only 774 MW of new generation and plant uprates cleared the auction.

Structural Challenges in Meeting Energy Demand

These numbers are not a one-off market anomaly driven by a single hot summer. They reflect a structural mismatch between the pace of electricity demand growth and the pace of new generation construction.

PJM has processed more than 170,000 MW of interconnection requests since 2023. Roughly 57 GW of projects have completed the study process and secured or been offered interconnection agreements. Many remain stalled by permitting timelines, supply chain constraints, and financing challenges that sit outside PJM's control. The timeline from interconnection application to commercial operation has stretched from less than two years in 2008 to more than eight years in 2025.

In 2025, PJM added approximately 2.2 GW of solar generation, along with 55 MW of wind and 29 MW of coal. The total new generation capacity connected is a fraction of the demand that continues to enter PJM's load forecast each year.

PJM's January 2026 Long-Term Load Forecast projects an annualized summer peak growth rate of 3.6% per year over the next decade. For context, the same metric in PJM's 2021 forecast was 0.3%. The growth rate has increased by a factor of twelve in five years.

NERC's 2025 Long-Term Reliability Assessment classified PJM at elevated risk for 2026 through 2028 and high risk starting in 2029.

The Price Cap Expires This Summer

One more detail that matters. The temporary price cap and floor that FERC approved for PJM's capacity auctions applied only to the 2026/2027 and 2027/2028 Base Residual Auctions. PJM estimated that without the cap, the 2027/2028 auction would have cleared at approximately $530/MW-day, roughly 60% above where it actually settled.

The next auction, covering the 2028/2029 delivery year, is scheduled for this summer. As of today, no cap is in place for that auction. Whether PJM and FERC reinstate a price collar or let markets clear unconstrained is one of the most consequential near-term market design questions facing the RTO.

An uncapped auction clearing at or near $530/MW-day would add billions in capacity costs to customer bills across PJM's 13-state footprint. For large commercial and industrial electricity consumers, capacity charges have already moved from a minor line item to one of the dominant cost drivers.

What Summer 2026 Looks Like

PJM's 2026 summer peak forecast projects approximately 156,000 MW under normal conditions. Last June proved that actual conditions can exceed "normal" by 7,000 to 8,000 MW.

The United States recorded its warmest March on record in 2026. NOAA's Climate Prediction Center shows above-normal temperature probabilities for summer across a wide swath of the country. A potential El Niño pattern is developing. Today's April Hot Weather Alert for the Dominion and Mid-Atlantic zones is the latest in a sequence of early-season thermal signals.

None of this is predictive. Weather in August is uncertain. But the structural picture underneath the weather is clear: PJM's demand is growing faster than its supply. The Dominion zone is absorbing the highest concentration of new load. Transmission infrastructure is years away from catching up. The capacity market has already signaled that reserves are too thin. And the pricing mechanism that held costs in check is expiring.

For energy traders, the summer peak windows carry more volatility risk than any in the past decade. For asset operators, dispatch decisions during high-load hours will face tighter margins and more frequent DR activations. For C&I organizations running facilities in PJM territory, capacity costs are now a strategic budget item, not an administrative one.

The organizations that will navigate this well are the ones making decisions from current data, not last quarter's report. In a market moving at this speed, the gap between seeing a signal and acting on it determines whether you capture the opportunity or absorb the cost.

Arcobi (formerly Arcus Power) tracks PJM market data, AI-powered forecasts, and asset dispatch signals across North American ISOs through DataHub, AI Forecasts, Dispatch, and Signal Orchestrator.

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