90 Percent of the US Population Would Die if the Grid Went Down for Six Months: The Sequence, in Order, and Why Nobody Would Stop It

Trace what half a year without current does to a country that has arranged its water, food, medicine, money, heat and light as children of a single machine, dependency by dependency, and then count who is still breathing at the end of the tracing.

90% of the population dead before the sixth month closes. That is the proposition, and the case for it does not rest on any single catastrophe. It rests on a hundred ordinary dependencies, each one rational on its own, which together make a country that cannot survive its own power supply going quiet.

What follows is a rehearsal first, because the closest thing to a controlled experiment happened in Europe less than two years ago and it lasted ten hours.

At 12:33 on the afternoon of 28 April 2025, voltage in the Spanish transmission system began to oscillate. Oscillation is routine on an alternating-current network, corrected within seconds by generators trimming their excitation or by transformers stepping taps up and down, and on an ordinary afternoon nobody outside a control room ever learns it happened. That afternoon the corrections arrived late and then arrived pointing the wrong way, and a grid that had been damping its own disturbance began instead to chase it, generators coming off the bus in clusters until the peninsula had shed essentially its entire load and sixty million people from the Algarve to the Costa Brava stood in the abrupt quiet of a country with the machinery switched off. (Most Aamericans aren’t prepared for what’s coming! when the world grinds to a halt.)

Spanish and Portuguese dispatchers had drilled for this. Every transmission operator in Europe runs restoration exercises, the procedures are written down by people who assume the worst day will arrive, and that afternoon the manual was executed by men and women who had read it before and rehearsed it under supervision while French and Moroccan capacity pushed current back through the interconnectors and did most of the labour of hauling the system up off the floor. Ten hours, near enough, from the first oscillation to a ragged approximation of normal.

A working day. Long enough, all the same, to stop trains in the open between stations and send passengers down the ballast in the heat, to evacuate the Madrid metro by hand one staircase at a time in the dark, to extinguish every traffic signal in two countries at once and reduce each junction to an improvised negotiation between strangers, to take out card terminals and the payment networks behind them so that shops which stayed open took cash or took nothing in a country where most people had stopped carrying cash years earlier. Aircraft were thinned to a handful, people were trapped in lifts that would not move and could not be opened without a key and a strong arm, and a small number of patients died through the ordinary attrition of machines that stop at the wrong moment. Their deaths were reported as footnotes.

Four hundred and forty of those afternoons, laid end to end, is what half a year amounts to, and the comparison is tidy and slightly misleading, because the same ten hours repeated four hundred and forty times would be a series of recoverable shocks rather than a collapse. Duration works on a disaster the way salt works on water — a little at a time, and then completely, until the thing in the glass has stopped being the thing you poured there. Every dependency in the country crosses from strained to dead on its own schedule, and each crossing strips away the tools needed to service the next one. Water goes before the hospitals can be resupplied, fuel goes before the water can be pumped, money goes before the fuel can be bought. The order is not random and it does not yield to improvisation at the scale of a nation, and the reason is arithmetic rather than psychology: a country of 335 million people has roughly 335 million separate arrangements for staying alive, and almost every one of them terminates in a wall socket.

Unforgiving is the word for that arithmetic, and what makes it so is that the American grid is not merely large. It is the load-bearing member of a structure built on top of it across a century, and the structure has grown so used to the member that it no longer carries any weight of its own. Water districts, hospital pharmacies, supermarket depots, dialysis chains, payroll processors, sewage authorities, grain elevators, cell networks, fire departments, the trucking firms that move everything — all of them were designed, decision by decision, on the premise that current is a utility in the older sense of the word, something always on tap and never worth insuring against. Each choice was rational in isolation. Taken together they amount to a single enormous wager on the continuity of one machine, and the wager has never been called.

Recent history supplies a rough and unsentimental ledger of how that machine behaves when something injures it. All of these happened. All of them ended, and the ending matters more than the severity, because in every case there was an outside world still working, with crews and spares and fuel trucks and a telephone number to ring.

1. 🇪🇸🇵🇹 28 April 2025, Spain and Portugal. Total system collapse across an entire peninsula in the middle of a working day, sixty million people affected, restoration in roughly ten hours. Investigators traced the sequence to voltage instability followed by cascading generator disconnection. The speed of the recovery rested on two advantages a continental outage would strip away: neighbours holding surplus, and a written procedure drilled in advance by the people who had to execute it.

2. 🌑 🇨🇱 25 February 2025, Chile. A transmission failure took the country dark from Arica to Punta Arenas, several million people, copper mining halted, a state of catastrophe declared within hours. Restoration consumed most of a day and delivered the particular indignity of a modern economy discovering how much ordinary commerce sits behind a payment terminal.

3. 🔫 🇺🇸 3 December 2022, Moore County, North Carolina. Two substations shot up with rifles by parties still unidentified, roughly forty-five thousand customers dark for days in early winter, schools and businesses closed across a county of pine woods and horse farms. Small arms, no engineering knowledge, days of disruption.

4. ❄️ 🇺🇸 February 2021, Texas. Winter Storm Uri, about four and a half million customers without power, roughly two hundred and forty-six deaths, most from hypothermia inside their own homes, boil-water notices eventually covering fifteen million people. The state had the rest of the country on the telephone and it still went that way.

5. 🕯️ 🇵🇷 September 2017 onward, Puerto Rico. Hurricane Maria destroyed the grid outright and full restoration took about eleven months. Excess mortality for the season was later estimated in the low thousands against a population of 3.3 million, a figure that sounds survivable until it is set beside the open port, the outside money and the mainland next door that made it so.

6. 💻 🇺🇦 December 2015 and December 2016, Ukraine. The first confirmed cyberattacks to take down a national grid. In the 2015 case operators were driven off their own control systems and restored service by hand, breaker by breaker — a preview of what a determined adversary can do to a machine designed to be operated remotely and trusted to behave.

7. 🎯 🇺🇸 April 2013, Metcalf, California. A sniper team removed seventeen transformers in nineteen minutes and cut fibre alongside them, coming within a hair of a wider cascade. The substation took months to rebuild.

8. 🕳️ 🇺🇸 August 2003, Northeast and Midwest. The largest blackout in North American history, fifty-five million people across eight states and Ontario, four days of restoration. Every event since has been measured against it and found smaller.

Three questions follow, taken in the order the failures actually arrive. Inside the house first, where water, heat and medicine run out at known intervals and the ninety-six hours after the lights go decide most of what comes later. Then the machine itself, with its transformer bottleneck, its fuel horizon and the long cannibalisation of a system that has to be eaten in order to be repaired. Survivors last, with the historical comparisons pushed until they break and the modest preparations that genuinely bend the curve.

Water leaves first, then the heat arrives, then the medicine runs out: the ninety-six hours that decide everything after

Pumps maintain municipal water pressure, and nothing exotic sits behind that sentence — centrifugal machines of a few hundred horsepower apiece, lifting water from river intakes and aquifers into treatment trains and driving it out into distribution mains under pressure, every stage running on current while the storage that lets a utility ride through a disturbance stays finite by design because reservoirs cost money and elevated towers are limited by physics and by the objections of people who have to look at them.

Between two and five days of falling pressure is what a city’s complement of water towers buys, depending on how much steel and concrete the ratepayers were willing to fund forty years ago, and demand spikes in summer shorten the window accordingly. Utilities with standby generation stretch it by a day or two and burn diesel doing so, a trade they make gladly and cannot sustain, until the taps cough, suck air and stop.

Texas in February 2021 ran the small-scale rehearsal. Treatment plants lost power, pressure collapsed across large parts of the state, and fifteen million people went under boil-water notices that assumed, with touching optimism, that they had gas or current with which to boil, many of them holding neither. Families melted snow on barbecues and filled bathtubs in the hour before the taps died. The state’s water sector turned out to have exactly as much resilience as everything else in it, which is to say the resilience that had been paid for, and little of that. Boil notices are a strange artefact of a rich country’s assumptions: they presume a pot, a heat source and a working pair of hands, and they presume that everyone reading the notice is literate, sighted and at home.

Wastewater follows about a day behind, because sewage travels by gravity to a lift station and lift stations are electric, unstaffed and numbered in the tens of thousands. Once the pumps stop, wet wells fill and overflow — into basements first, then creeks, storm drains, the water table — and a country with dead treatment plants and overflowing sewers is a country where dysentery stops being a travel anecdote and becomes a routine diagnosis, with cholera moving from improbable to merely unlikely. Chlorine and coagulants and lime are a supply chain of their own, trucked in weekly by firms that are also dark.

Firefighting collapses in parallel and faster than people expect. An engine carries perhaps five hundred to a thousand gallons drawn from hydrants fed by the same dead mains, and once the tank is empty the crew is a spectator with a hose and a good view while a kitchen fire that would have cost one room takes the house and the house takes the block, because the block is timber and dry and every other engine is in the same condition. During the 1977 New York blackout, arson and unattended candles levelled long stretches of the South Bronx and Bushwick. The fire service then had water and fuel and still lost neighbourhoods.

Behind all of it stands the domestic machine, which has quietly become an electrical appliance. Air conditioning stopped being a luxury in the United States somewhere in the 1970s and became a condition of habitability across the Sun Belt, the interior West and increasingly the Northeast, and roughly two-thirds of American homes now depend on it. Take the compressor away in July in Phoenix or Dallas or Atlanta and a sealed modern house becomes a masonry box that has spent all day absorbing sunlight, with interior temperatures passing thirty-two degrees Celsius inside a day and thirty-five within two, then climbing toward the ambient peak. Cognition degrades first, then judgement, then the capacity to notice that a person is in trouble and ought to be doing something about it, which is why heat deaths cluster among people found alone indoors with a window open and a full glass of water beside them. Above forty degrees the nightly recovery window closes altogether, three nights without relief is where the very old and the very young begin dying in numbers, and the fourth is where the merely middle-aged and unwell join them.

Thin already is the margin, and worth pausing on. The 1995 Chicago heat wave killed more than seven hundred people in five days with the grid fully operational, and the 2021 Pacific Northwest heat dome killed hundreds in a region that had never needed cooling and still does not mandate it. Those dead were overwhelmingly old, poor, isolated and living alone on upper floors, a population a blackout does not create so much as expose. Remove the hospitals and emergency departments and morgues and ice and fans and the ability to drive somewhere cooler, then stretch the condition from June into November, and the mortality curve stops being a total and becomes a shape.

Deeper and more slowly, cold works. A sealed house in January loses heat to the ground and the outside air until the interior settles perhaps ten to fifteen degrees above ambient, which in Buffalo or Minneapolis means below freezing for weeks, and water pipes in exterior walls burst on the first hard night and flood the very basements into which families retreat. A gas furnace is useless without its electric blower and ignition board, so even a pressurised gas main heats nothing, and while wood stoves and fireplaces exist in a minority of homes, the wood supply in a suburb in February is whatever was left from the previous autumn. Households with a woodlot and a chainsaw do well. Households with a decorative gas log set discover the distinction on the first night. Hypothermia indoors is a strange way for a rich country to lose people and it runs quiet — confusion, then sleepiness, then a night that does not end — and Texas lost around two hundred and forty-six people to a week of it, most in their own houses, in a state with the rest of the country on the telephone.

Medicine is where the schedule tightens to something close to an execution date. Around five hundred and fifty thousand Americans receive dialysis, most three times a week, each session requiring a machine, a trained operator and something in the order of a hundred and twenty litres of purified water, and potassium begins to matter after three missed sessions while the heart is at genuine risk by five. Dialysis units run on generator until the diesel stops and then close. During the Texas freeze, centres shuttered across the state and patients were told to restrict fluid and potassium and wait, and some of them died waiting.

Worse again is home oxygen, because it lives in the house: concentrators draw current, a portable cylinder gives a couple of hours, a liquid reservoir boils off on its own within days, and roughly one and a half million Americans use long-term oxygen therapy with a large fraction unable to cross a room without it, which means they cannot queue for water, cannot walk to a distribution point and cannot leave. Insulin degrades at room temperature over about a month and faster in a hot kitchen, roughly eight and a half million Americans depend on it, syringes and pens and test strips and lancets are consumables in a supply chain that has stopped, and diabetic ketoacidosis, which killed within days in the years before insulin existed, returns as a house call nobody is in a position to make.

Beyond those three sit home ventilators, infusion pumps, enteral feeding, apnoea monitors and the whole pharmacopoeia of chronic illness. Six in ten American adults take a prescription drug and a great many take something they cannot skip for a week without consequence; statins and antihypertensives can be interrupted at a price, while antiepileptics, anticoagulants, antipsychotics, immunosuppressants and thyroid replacement cannot. Pharmacies hold days of stock rather than weeks, and their inventory systems are cloud-hosted, which means the pharmacist cannot even tell you what is in the drawer.

Hospitals absorb the first wave and then stop being hospitals. Federal rules require roughly ninety-six hours of on-site generator fuel, which is four days, plus stored water and a written plan, and four days buys a switchover, a stabilisation and a few surgeries before the building becomes a well-equipped shell without air conditioning, working lifts, imaging or a laboratory, staffed by nurses who cannot be paid, relieved or fed because the roads are dry of fuel and the tills are dead. Surgery continues for a while on the strength of habit and skill and then stops for want of sterile drapes, and anaesthesia without a ventilator is a craft largely abandoned in the 1950s that would have to be relearned in a fortnight.

Changes character somewhere in the second week. It stops being an emergency, which is a thing with an end, and becomes a condition, which is a thing you live inside. Ambulances run until they are empty and then park, elective care disappears, wound infection becomes the leading cause of surgical mortality for want of antibiotics and sterile supply, and bedbound residents of nursing homes, of whom there are around 1.2 million, begin dying of dehydration and pressure sores in buildings with no lifts to move them and staff who cannot get to work. Bodies become a logistics problem in their own right, which nobody plans for because in ordinary life they are collected within hours; refrigerated trailers get requisitioned by whoever has the diesel to run them, and summer is worse than winter, since winter at least provides a morgue out of doors until it provides a thaw.

Early-twentieth-century in its medicine and pre-industrial in its logistics is what the country has become by this point, and it is doing both with a population that remembers neither and expects better.

A machine that must be eaten to be repaired: transformers nobody can replace, diesel nobody can pump, and a queue longer than the outage

Scale comes first, because the American grid is not a system in the sense a layman means. Roughly 160,000 miles of high-voltage transmission cross the country, strung between towers in desert, forest, farmland and mountain pass, and beneath and beyond that lie about 5.5 million miles of distribution line, most of it overhead and much of it threaded through trees that are never cut back far enough. Around 55,000 substations sit on the network along with more than 12,000 generating plants of wildly varying size, and three asynchronous interconnections — Eastern, Western, and the deliberately isolated Texas system — touch one another only through a small number of direct-current ties, so that a fault in one cannot cascade into another and one cannot rescue another in any meaningful volume.

Some three thousand entities own and operate this apparatus: investor-owned utilities, municipal systems, rural cooperatives, federal marketing administrations, a haze of independent generators and marketers. Coordination runs through the North American Electric Reliability Corporation as the designated reliability organisation under federal oversight, and through regional councils and independent system operators. The arrangement produces excellent day-to-day reliability and a chronic diffusion of responsibility for anything long-term, which is why resilience has been argued over in regulatory filings for two decades while very little of it got bought.

Worse still, the metrics are pointed the wrong way, and not by accident. Reliability in this industry is measured by the duration and frequency of customer interruption, how fast the lights come back and how often they go, and both are honest measures of what they measure. Neither says anything about whether a system can hold out for a month, because a network that restores in four hours and a network that restores in four days score identically as long as the interruptions stay short. Endurance has no line on the form, and what has no line on the form does not attract capital.

Nodes on which the architecture hangs are the large power transformers. Anywhere from fifteen hundred to two thousand units above a hundred megavolt-amperes sit in the bulk system, most of them decades old, each effectively bespoke — wound for one voltage, one impedance, one footprint, one set of thermal and seismic conditions, one site. A single unit weighs hundreds of tons, moves by rail or heavy-haul road under permit, and is lifted onto a pad poured for it alone. Nothing about the object is modular; it is a piece of civil engineering that happens to be electrical.

Ordering from stock does not solve replacement. Before 2020 the largest classes took a year to eighteen months, lead times have roughly doubled since, and the trade press reports waits of two to four years driven by demand from data centres, electrification and grid rebuild programmes worldwide. Domestic capacity is thin and concentrated in a handful of plants, the grain-oriented electrical steel for the cores comes from a single American producer with the remainder imported, and bushings and tap changers come from a small international pool that is not large. A bushing is a porcelain tube the height of a man that keeps high voltage from arcing to earth, and there are perhaps four factories on earth worth naming.

Spares exist in small numbers, shared through a voluntary industry pool, and the Department of Energy keeps a modest stock of recovery units for exactly this class of emergency, but against a national event the arithmetic fails badly: destroy a tenth of the installed base and the replacement queue exceeds the entire world’s production of large transformers for several years running.

Central mechanism of a six-month outage, and the reason it differs in kind from a long storm restoration, is that the grid gets eaten in order to be repaired. Crews strip de-energised equipment to keep live equipment alive, a transformer comes out of a town already written off and goes onto a pad in a town still worth saving, and bushings and relays and cable and switchgear and copper all migrate while restoring one feeder means sacrificing three. Engineers call this triage in writing and cannibalisation out loud. It is the only way to run a repair programme against a supply chain that has stopped delivering, and it produces a moral problem the industry has never had to solve at scale, which is which towns get written off, who decides, and on what evidence, in the absence of a working telephone.

Quieter constraint, and easily overlooked, is labour. Line work is a skilled trade with an ageing membership, the crews who would do the rebuilding are themselves residents of the affected area with flooded basements and stranded families, and mutual aid brings outsiders for a fortnight before those outsiders go home because they have jobs and households of their own. Six months is not a mutual aid problem, it is a staffing problem, and the country trains lineworkers at a rate calibrated to attrition rather than to catastrophe.

Second constraint, binding earlier than most people expect, is fuel. Retail petrol is drawn from underground tanks by submersible pumps and dispensed by machines that need current and a working payment terminal, so a station with a generator sells for as long as its tank lasts, which along a suburban corridor is a matter of hours. Tankers that would refill it run on diesel, the terminals that load them need power, and the refineries that supply the terminals are continuous-process plants that do not enjoy being shut down and restarted, several of which will stay down for the duration rather than attempt it. Restarting a refinery from cold takes days and is done in a strict sequence by people with instruments, and a plant that loses instrument air mid-shutdown can coke its furnaces and be out of service for months. Strategic reserves exist and are enormous on paper, but crude in a salt cavern is not diesel in a truck and the distillation capacity to convert one to the other sits inside the refineries that are dark. Military and emergency allocation will cover the National Guard, the hospitals that remain and the restoration crews themselves, roughly in that order and none of it generously.

Down the same hole follows food distribution. Grocery logistics in the United States runs on a just-in-time model refined to the point that the Food Industry Association has long put average store inventory at around three days, so the shelf is a pipeline rather than a warehouse and the pipeline is empty. Refrigeration fails first: frozen and chilled cases hold temperature for a few hours if the doors stay shut and the staff know to keep them shut, which at the start nobody does, and behind the store sits a cold chain of refrigerated warehouses, distribution centres and diesel reefers all dependent on the same missing fuel. Home freezers extend the window to forty-eight hours unopened, which is why the first genuinely social behaviour of a long blackout is a vast and faintly festive block party of grilled meat and the second is food poisoning from whatever people did not get to.

Pastoral the countryside is not, whatever the brochures suggest. Irrigation pivots run on electric motors, confined livestock sheds run on feed augers and water pumps and ventilation fans, and a modern broiler house without fans in August loses its flock within hours. Milking parlours are electric and a dairy cow not milked twice a day develops mastitis inside a week, grain elevators and feed mills and packing plants and cold stores all stop together, and the whole chain from field to freezer sits waiting on a fuel truck that is not coming. Nobody starves in the first month, and that deserves saying plainly because the popular imagination jumps straight to famine. America grows an enormous caloric surplus and stores much of it as grain in silos that do not spoil in six months, and the difficulty lies in movement and milling and cooking and in the fact that the agricultural system is itself a heavy consumer of precisely the thing that has vanished. Monotony arrives first, then deficiency, then real hunger among the people who were already food-insecure and among city populations with no working link to farmland.

Ninth day is about when money stops being money. Cash disappears from both directions at once, because nobody can withdraw it and nobody can spend it digitally, payment processors and card terminals and the interbank settlement layer all need power and connectivity, and direct deposit stops with them while rent and mortgages and insurance premiums and interest keep accruing against accounts nobody can inspect. Within a fortnight the country is transacting in physical notes it had largely stopped using, and the supply of notes is nowhere near adequate. Prices do what prices do: water, fuel, generators, batteries, ice, insulin, ammunition and cigarettes clear first and hardest, most states have price-gouging statutes that trigger on a declared emergency, enforcement in a blackout is theoretical, and the market clears at whatever the seller believes the buyer will bear. Every disaster produces the same argument about whether that is exploitation or exactly the signal that moves stock toward scarcity, and the argument is never settled before the stock runs out.

Petty rather than apocalyptic is how security degrades, and no less corrosive for that. Generators are loud and heavy and valuable and running in the dark, and they walk away; fuel is siphoned from parked cars, a skill nobody under forty has practised; copper leaves substations; vacant houses are entered. Theft is opportunistic and local at first, which makes it harder to deter than organised theft would, because there is no pattern to patrol against and the patrol itself is on foot.

Quietly and early, communications go. Cell sites hold four to eight hours on battery and a day or two on generator if anyone brings fuel, the backhaul that joins them is fibre with powered repeaters every few kilometres, and public safety answering points have their own backup and their own fuel horizon. Once the phones fail, information reverts to rumour and to radio, and the AM band — unfashionable, analogue, immune to packet loss — becomes the most valuable spectrum in the country for the handful of people who own a receiver and know which frequency carries the emergency broadcaster.

Soft in ways recent events have made vivid, the grid itself. Substations are fenced, remote, unstaffed and full of metal. In Moore County somebody shot up two of them with rifles and put forty-five thousand people dark for days, and Metcalf took similar treatment in 2013 when a team removed seventeen transformers in nineteen minutes and came within a hair of a wider cascade. Both attacks ended because the rest of the system held, and neither would have ended anything in a country where the rest of the system was already down.

Crawl rather than switch is what restoration from a national collapse would be, and the mechanics explain the calendar. Bringing a dead interconnection back is called black start, and it proceeds by cranking generators that can start without an external supply — hydro units, some combustion turbines, a few diesels — then energising short stretches of transmission, then picking up load in small increments, stabilising and moving on. Each step is delicate. Energising a line produces charging current from capacitance alone, and picking up a cold neighbourhood draws several times normal load because every compressor and pump and heater in the block starts at once, which is why restoration crews speak of cold load pickup with the particular respect reserved for things that can undo a day of work in a minute and why they pick up a few blocks at a time rather than a few streets.

Four days was enough for the 2003 cascade to unwind across fifty-five million people with the entire rest of the continent available to help, and NERC’s own restoration literature talks in weeks for a full interconnection under favourable conditions. Six months is not favourable conditions. Six months is what happens after the spares run out and the crews run out and the fuel runs out, when the country discovers that the difference between four days and a hundred and eighty is not a factor of forty-five but a change in kind.

Counting the survivors: what Iberia and Ukraine really settled, where death concentrates, and the modest things that actually bend the curve

Bending the argument is what honesty requires here, because a number repeated with too much confidence begins to look like a slogan, and the record does contain real grounds for doubt.

Puerto Rico lost essentially its whole grid in September 2017 and did not lose ninety percent of its people. The island’s official excess-mortality estimate for that season ran to roughly three thousand against a population of 3.3 million — dreadful, and a rounding error in proportional terms. Ukraine has absorbed four winters of deliberate strikes on generation and transmission, has run millions of people through long unheated stretches, and has kept its toll in the low thousands above baseline. Spain and Chile both went dark in 2025 and recovered within a day or two.

Four things separate those cases from a continental six-month event, and each does heavy work. Climate comes first: Puerto Rico is tropical and its people cook outdoors all year. Ukraine kept a functioning state, a war economy, an external supply of transformers and generators, and a grid battered but never uniformly absent, with repair crews working under air defence and generation distributed widely enough that pockets always survived. Spain’s collapse was regional inside a continent and Chile’s was short. None of them was a simultaneous half-year loss of supply across a country where most homes need current to stay habitable in either season.

Scale is the second. Puerto Rico covers a hundred miles by thirty-five and would fit inside the Houston metropolitan area several times over, and mutual aid works at island scale in a way it cannot work when forty states are in trouble at once and the same line crews cannot be in forty places. Outside world is the third, and every analogue above had one: aid flew in, spares were shipped, money arrived, ports stayed open or reopened. In a national event that world sits at arm’s length across an ocean, and its transformers are already spoken for by whoever ordered them three years ago.

Dependency is fourth, and most important. Puerto Rico’s population skews younger than the mainland’s and, crucially, less medically tethered, and Ukraine’s grid losses fell on a population with little air conditioning and little home medical equipment. The United States is the most thoroughly electrified and most thoroughly medicated large population on earth, and it has arranged its housing stock and its food system and its water system and its medicine around an assumption of continuous supply that has held for a century.

Ceiling rather than forecast is what ninety percent is best understood as, and the more useful question is not how many die but who, where and in what order. Survivors would not be the strong. They would be the well-situated, and the correlation between situation and income is close to perfect. A rural household with a well and a hand pump and forty acres and a woodlot and a chest freezer full of meat runs very little risk for a very long time; so does a coastal California town with a mild climate and a municipal supply still moving under gravity; so do the Amish and Mennonite communities, who have run without the grid for two centuries and would find the rest of the country suddenly and awkwardly interested in their methods.

Precision, brutal and exact, is how death concentrates on the already-dependent: the oxygen patient on the third floor of a walk-up, the dialysis patient eleven miles from a closed unit, the insulin-dependent teenager whose mother cannot reach a pharmacy, the nursing-home resident nobody can lift, the asthmatic in a hot apartment above a shut intersection. It clusters geographically in Sun Belt metros, in older inner-ring suburbs with ageing populations and no shade, in rural counties whose hospital closed in the past decade, in high-rise public housing where the lifts stop on the first day and the water stops on the third.

Second-order migration is what that distribution produces, worth anticipating and rarely discussed. Within a fortnight the mobile begin to move, toward relatives and farmland and anywhere with a well, highways become corridors of pedestrians and of cars that run until the tank is dry and are then abandoned on the shoulder, and the people who leave are the ones with somewhere to go and a vehicle to get there. The people who stay are the ones with neither, and the towns they leave lose their last spare capacity in the same motion while rural counties that were supposed to be refuges acquire within a month a population of arrivals with no land, no water rights and no local standing. The goodwill that greets the first fifty strangers curdles somewhere around the five hundredth.

Queue is what federalism becomes once the disaster is national. Mutual aid compacts are excellent and assume most of the country is fine; FEMA coordinates and reimburses and owns neither the transformers nor the water utilities nor the hospitals nor the trucks; the National Guard can move water and provide security and run communications, and it also needs fuel, and its fuel comes through the same dead system. NERC’s GridEx series has exercised a nationwide cyber-physical attack repeatedly, and the consistent lesson from every iteration is that recovery runs slower and messier than the participants expect.

Time is what a short list of things genuinely buys, and it is worth stating specifically because vague exhortation is what usually gets written. Institutionally, the highest return comes from islanding rather than hardening: a hospital or water treatment plant or fire station that can run on its own solar array and battery bank for a fortnight is worth more than a rebuilt transmission line, because it stays useful while the line is down. Standardising transformer designs so one spare fits more than one site, restoring domestic grain-oriented steel capacity, keeping real on-site fuel reserves at critical facilities and funding a genuine national stock of recovery transformers all matter more than current allocations suggest, and data centres, which have driven load growth and capacity-auction prices to extraordinary levels over the past three years, are also the most easily islanded large loads in the country and could carry part of the burden if anyone required them to.

Unglamorous and cheap, the domestic list. Two weeks of stored water at a gallon per person per day is the entry ticket, and the households that do well have a rain barrel or a hand pump or a creek behind them, along with a means of cooking that needs neither gas nor current and fuel for it, light that needs no batteries, warm bedding and the discipline to close off a single room, a battery radio because the AM band still works when everything else fails, cash in small bills, paper copies of prescriptions and a fortnight of the drugs themselves. Most of it costs less than a year of streaming subscriptions, and the reason people do not do it is that the lights have always come back on.

Long after the point at which most of the country has stopped expecting it, the end arrives as a crawl rather than a switch: generators cranked one at a time, lines energised in short stretches, load picked up in increments while the neighbourhood returns a block at a time.

What six months exposes is not a shortage of transformers or diesel. It is that the United States built a machine of extraordinary sophistication and then arranged every other system — water, food, medicine, money, heat, light — as a child of that machine, with no independent means of life. Four days of hospital fuel. Three days of supermarket stock. Two days of cell battery. A country can run on margins like those indefinitely, right up until the moment it cannot.

Eventually the lights come back on. The question that outlives the outage is who is still in the house when they do.