How the Lights Stay On

Chapter 1: The Blink

On the afternoon of August 14, 2003, the lights went out across the northeastern United States and parts of Canada. They went out fast — within seven minutes, fifty million people had lost power.

In New York City, the elevators stopped between floors. The computers blanked. The air conditioning died and offices got hot quickly. People wandered out into the streets and started walking. Some walked across the Brooklyn Bridge in the August heat, dress shoes in hand, bottled water passed from stranger to stranger.

And under the streets, in the subway tunnels, the trains had stopped between stations.

That was the scene that played on every television screen for the next two days. Subway cars halted in the dark, hundreds of passengers inside, the air growing close. New York City police officers arrived at the emergency shafts — the ventilation wells that come up through the sidewalks — and lowered themselves down into the tunnels with flashlights. Then, car by car, train by train, they led people out. Office workers in suits and dress shirts. Women in skirts and heels. Tourists with shopping bags. They walked single file along the dark tracks, careful of the third rail, with a police officer’s flashlight bobbing somewhere ahead. They climbed up ladders inside the ventilation wells, hand over hand, and emerged through grates in the sidewalks of Manhattan, blinking in the late-afternoon sun, while crowds gathered on the curbs to help them up. Heels in one hand, briefcase in the other.

You did not have to be in New York that day to remember it. The whole country watched.

At an office where a friend of mine worked, the AC gave up and the staff started to leave — but how were they going to get home? The trains were not running. The buses were stuck in traffic that no traffic light could untangle. There was one car in the parking lot. It belonged to the office boy, a young guy who drove in every day because he ran the company’s errands. So he drove everyone home, one by one — across boroughs, into New Jersey, out to the suburbs — for hours and hours, dropping off the executives and the accountants and the receptionists at their doorsteps as the sun went down on a city that could not turn on its lights.

By the time he finished, it was the middle of the night. He had become, for one strange afternoon, the entire transportation system of his small piece of the world.

That blackout is a story we’ll come back to. We’ll trace it minute by minute later in this book — what caused it, why it spread so fast, how a tree branch in Ohio could darken New York City. But right now I want to start somewhere much smaller.

I want to start inside an apartment.

A few years later I lived on the New Jersey side of the Hudson River, in an old apartment building in Hoboken. The building was old enough that the wiring inside the walls had not really been designed for what people now plug into them.

Here is what happened every August night.

I would come home, sweaty, and turn on the air conditioner. There would be a hum from the window unit as the compressor kicked on. And in the exact moment that hum started, the bulbs in my apartment would dim — just for an instant — and then come back to full brightness.

A blink. So fast you’d miss it if you weren’t looking. Almost too fast to be sure you saw.

But once I noticed, I could not unsee it. Every night, same thing. The AC clicks on, the bulbs dip, the bulbs recover.

For a long time, I figured this was just a quirk of an old building. Something to roll my eyes at and forget. Then I started reading about how the grid works, and I realized something surprising:

The Blink in my Hoboken apartment, and the Blackout that took down fifty million people, were the same thing. The same physics. The same kind of failure-in-miniature. Just at different scales.

That is what this book is about.

To see why, we need to spend a minute on what is actually happening when your bulbs dim.

An air conditioner is mostly a motor. Inside the compressor, there is a heavy metal shaft that has to start spinning every time the AC clicks on. Getting a stopped motor spinning takes a lot of electricity for a very brief moment — usually somewhere between five and seven times the normal running current. This sudden gulp of electricity has a name. Engineers call it inrush current.

The wires in your wall are not magic. They look like simple metal, but they have a tiny amount of resistance, the way a garden hose has a tiny amount of friction. When a sudden spike of current rushes through a resistive wire, the voltage — the push behind the electricity — dips for a moment. Less voltage to your light bulbs means less brightness. Then, a heartbeat later, the motor is up to speed, the current drops back to normal, the voltage recovers, and your bulbs are bright again.

That is the Blink. Inrush current → voltage sag → dim bulb → recovery. The whole thing happens in less than a second.

A modern building with thicker wires, a larger service panel, and a properly sized transformer on the pole outside will hide the Blink almost completely. You won’t see it. The electrons will smooth it over before your eyes can catch it. But the physics is still there, every time the motor starts. The grid is just absorbing the punch quietly enough that you don’t notice.

Now imagine a million air conditioners.

It is six o’clock on a Tuesday in August in a major city. The temperature has been climbing all day. Office workers are coming home. They walk in, drop their bags, and turn on their ACs. Not all at the exact same instant — but close. Within a few minutes, across a whole metropolitan area, millions of compressor motors are pulling their inrush currents nearly simultaneously.

Somewhere, far from any of them, power plants have to catch that. They have to push more current into the grid right now, this second, to keep the voltage from sagging citywide. If they can’t, every bulb in the city would dip — and worse, sensitive equipment in hospitals, data centers, and factories would start to fault.

This is happening every minute of every day. The grid is one giant, synchronized machine, and somewhere — in control rooms in Pennsylvania and Texas and Ohio and California — there are people watching screens, watching frequency and voltage, making sure the grid catches every punch the world throws at it.

When the grid catches the punch, you don’t notice. You make dinner. You watch TV. You go to sleep.

When the grid misses the punch, that is what 2003 was.

A tree branch in Ohio touched a sagging power line. A software bug in a control room meant no alarm went off. By the time anyone realized what was happening, the imbalance had cascaded across the entire eastern grid. Within seven minutes, the system had shed fifty million customers to save itself from physical destruction.

The Blink in my apartment was the grid catching a punch — barely, sloppily, but catching it. The Blackout was the grid missing one.

Here is the single most important fact about electricity, and it is so strange that most adults never really absorb it.

Electricity is made and used in the same instant.

The toast you ate this morning was generated in a power plant maybe a hundred miles away, less than one second before you ate it. The fan spinning in your room right now is being powered by a turbine spinning at this exact moment in a plant you have never seen, maybe burning gas or splitting atoms or being pushed by the wind. There is no warehouse of electricity sitting around waiting to be used. There is no giant bucket of stored electrons under the city. The grid is making your electricity as you read this sentence.

That is what makes electricity different from almost everything else humans deal with. Most things you can stockpile. You can buy a thousand cans of soup and put them in a basement and eat them next winter. You cannot do that with electricity. Batteries are a way around this — we’ll spend a whole chapter on them later — but batteries are expensive and limited, and at the scale of a whole country they store only a tiny fraction of what we use.

This means the grid has to perform a feat of balance every single second of every single day. Supply has to match demand exactly. If a million people turn on their ACs at six PM, somebody, somewhere, has to be running a turbine harder right now to meet that load. If a cloud passes over a giant solar farm, somebody has to make up the difference in the next few seconds, or the lights go dim.

The Blink in my apartment was that balance, almost failing, then recovering. The Blackout was that balance, failing, and the rest of the grid running for the exits.

Almost everything in this book — solar panels, battery walls, the grid of the future, why people in Texas lost power in a snowstorm, why China can build transmission lines that the United States can’t — is downstream of this one fact. Electricity has to be made and used in the same instant. Everything else is a consequence.

If you remember nothing else from this book, remember the Blink.

Pay attention next time you turn on something big. A microwave. A hair dryer. A vacuum cleaner. Watch the lights — really watch them — and see if you can catch the dip. In a new building you probably won’t. In an old building you might. Either way, you’ll know what just happened. You’ll know that the wires in your wall just experienced, in tiny form, the same thing the entire eastern seaboard experienced on August 14, 2003.

By the time we’re done with this book, you’ll see the grid everywhere. You’ll understand why a tree branch in Ohio could darken Manhattan. You’ll know why some roofs have solar panels and others don’t. You’ll know what a home battery actually does, and when it makes sense to buy one, and when it doesn’t. You’ll know what is happening when the lights in your school flicker during a thunderstorm. You’ll know what the people in those control rooms are watching for, and why their job is one of the most quietly important in the country.

But first, the Blink. Watch for it tonight.

All 18 chapters of How the Lights Stay On · Library · All courses