Why the Lights Flickered From D.C. to Chicago: Inside the Power Strain Behind Northern Virginia Data Centers

A Ten-Minute Wobble That Reached Six States

For about ten minutes on a Wednesday morning, refrigerators buzzed strangely and air conditioners made noises they shouldn't make, in homes hundreds of miles apart. The disturbance traced back to Northern Virginia data centers, where lights flickered as something upstream went briefly, invisibly wrong. People in Chicago felt it too, though most had no idea why. Nobody lost power. No headline event announced itself. And yet something had clearly gone wrong somewhere in a part of the electric system most Americans never think about until it hiccups.

The cause traced back to a single transmission line going out of service in northern Virginia, and to a reaction that followed almost instantly: a cluster of data centers, sensing the disturbance, automatically unplugged themselves from the grid and switched to backup power. Grid operator PJM registered more than 3 gigawatts of demand vanish in an instant, about 3% of everything the system was carrying at that moment. Dominion Energy, the utility serving the region, said its team stabilized the situation within minutes. But a sensor network run by Ting Labs recorded voltage disturbances rippling along the entire eastern seaboard and into the Midwest, and its CEO, Bob Marshall, called it a genuinely massive event, one that took roughly ten minutes to fully settle rather than the milliseconds such disruptions usually take.

Northern Virginia data centers didn't cause a blackout that day. But the event revealed something more interesting than an outage would have: how much of America's electrical stability now depends on machines built to protect themselves first, and how little cushion exists between normal operation and a system-wide wobble that regulators can measure but not fully explain.

Data Center Alley, Explained in Scale

The place where this happened has a name inside the industry: Data Center Alley, a stretch of Loudoun County and its surrounding jurisdictions that now holds the largest concentration of data centers on Earth. Northern Virginia alone hosts an estimated 35% of the world's data centers. Loudoun County by itself contains roughly 200 of them, and half of those sit in a single state legislative district.

These are not the server rooms people picture from a decade ago. A modern data center is often the size of a big-box department store, built specifically to run computers and networking equipment around the clock, without pause, because the internet doesn't take a lunch break. Cloud storage, streaming, e-commerce backends, and increasingly the compute-hungry training and operation of artificial intelligence systems all live inside these buildings. A single facility might draw between 20 and 50 megawatts at peak. The recently approved facility in Appomattox, a small town far outside the traditional data center corridor, will draw 300 megawatts on its own — roughly equivalent, in raw demand, to what a small city needs.

Why This Surfaced Now

The July disturbance drew national wire coverage because it was measurable, sudden, and geographically vast for something so brief. Reuters reported it as a story about grid physics and utility competence under stress. But the event was really a symptom of a slower-moving story that Virginia's own legislature had already been warned about seven months earlier, in a December report to the General Assembly that projected the state's power demand could rise by up to 183% by 2040, driven almost entirely by data centers.

The Man Who Thinks Blackouts Are Coming

Gary Wood has spent more than 30 years in electrical engineering, and he runs Central Virginia Electric Cooperative, the utility that will help power the new Appomattox data center. He is, by his own account, genuinely excited about that project and what it could mean for a part of the state that has gone a long time without major new investment. He is also blunt about what he thinks is coming.

"I have said that on a personal basis, I believe we will have rotating blackouts before this gets resolved," Wood said. He expects it within three to five years across PJM, the regional grid that spans all or part of 13 states and serves 67 million people.

Rotating blackouts, sometimes called rolling blackouts, are not system failures in the dramatic sense. They're a controlled response: a utility deliberately cuts power to one group of customers for about half an hour, restores it, then moves the cut to another group, spreading the pain so the whole system doesn't collapse at once. Texas experienced this in 2021, and it made national news. Virginia has not experienced it in living memory — but Wood says the state came close during a cold snap in December 2022, and the math has only gotten tighter since.

Twenty power generation facilities in PJM's territory, including two of Dominion's in Virginia, closed between May 2023 and April of the following year. Twenty more, including two Appalachian Power units in Buchanan County, are scheduled to close by the end of 2028. Demand is rising while supply is retiring — and the retirements are running on a faster clock than the replacements.

One Law Creates the Obligation, No Law Creates the Supply

Here is the mechanism at the center of Wood's worry, and it's a genuinely strange piece of policy architecture once you see it clearly. Virginia law requires public utilities to connect any new customer who requests service within their territory. There is no equivalent requirement — no law, no PJM market rule — that forces a utility to build new power generation to match that growth. The obligation to serve exists. The obligation to supply does not.

Virginia Del. David Reid, whose Loudoun County district contains roughly half the county's 200 data centers, reads the situation differently. He points to language in the state's own Joint Legislative Audit and Review Commission report, which found that while utilities must serve new customers, they are not required to do so immediately, and their foremost responsibility is protecting the reliability of the grid before adding large new loads. "The way that I read that and put it into kind of layman's terms is that utilities do have an obligation to serve new customers, but not at the risk of existing customers," Reid said.

Wood doesn't dispute the legal reading. His concern is structural rather than semantic. PJM is a regional grid spanning 13 states, which means a Virginia utility's decision to slow-walk a data center connection doesn't actually solve anything if a neighboring utility in Pennsylvania, Maryland, or Ohio says yes instead. "The question of generation capacity is regional, not local," Wood wrote in an email. JLARC's own report recommended that lawmakers clarify utilities' authority to delay, but not deny, service when a new customer's load can't be supported — a fix that would at least buy time. The 2025 General Assembly session did not take it up.

What 30,000 Gigawatt-Hours Actually Means

JLARC's modeling projected that Virginia's future consumption, driven largely by data centers, would require more than 30,000 gigawatt-hours per month. A single gigawatt equals a billion watts — the Department of Energy puts that at roughly two million solar panels or 103 offshore wind turbines' worth of generation. Strip away the new data center demand entirely, and Virginia would still need 15% more energy than it uses today. The report's own language about meeting the higher, data-center-driven demand is unusually candid for a government study: it calls the goal "difficult to achieve" at best.

A December letter from PJM's board chairman, Mark Takahashi, to the grid's stakeholders put data center growth at the top of a list of forces straining the system's supply-demand balance, alongside the fast retirement of coal plants and the slow arrival of replacement generation due to siting, permitting, and supply chain bottlenecks. He called it "a generational change in our industry that requires both thought leadership and action" — while acknowledging that even the regulatory fixes underway would not fully "resolve the challenge."

A continent-wide reliability study published by the North American Electric Reliability Corporation in December placed Virginia, along with more than half of North America, at elevated to high risk of an electricity supply shortfall. The report singled out Loudoun County by name as home to the largest concentration of data centers in the world, and noted that the pace at which such facilities can be built and connected creates real challenges for forecasting demand accurately. Notably, the report found that winters, not summers, have become the higher-risk season for supply shortfalls in this region — a reversal of the traditional pattern that most grid planning was built around.

The Bill Arrives Before the Blackout Does

Even if rolling blackouts never materialize, the cost of avoiding them is already landing on ordinary electric bills. A report from Monitoring Analytics, PJM's independent market monitor, found that current and planned peak power demand added nearly 12,000 megawatts to next summer's expected peak — increases that were, in the words of its president Joseph Bowring, "almost entirely due to existing and projected large data center load additions to the PJM grid."

That demand growth drove PJM's most recent capacity auction — the mechanism by which the grid pays power generators to guarantee future supply — up by $7.2 billion, an 82% jump. More than $16 billion in those guarantee payments gets passed straight through to utility customers across the 13-state region. Separately, the Union of Concerned Scientists calculated that $4.3 billion in transmission expansion costs were charged to consumers across seven PJM states last year alone, tied to more than 150 local transmission projects between 2022 and 2024 that existed for one reason only: connecting data centers to the grid.

The Natural Resources Defense Council's projection is the starkest of the three. It estimates PJM consumers could see a cumulative $163 billion in added utility costs through 2033, driven by the same capacity-auction mechanism, once negotiated short-term price caps expire around 2028. By NRDC's math, an average family in the region will be paying roughly $70 more a month by 2028 because of data center growth — and, as the report pointedly notes, that bill arrives whether or not all the data centers currently being planned actually get built.