How Ukraine Won the War to Keep the Lights On

Electric trams are running again in Kyiv, and electric scooters dot the sidewalks. With curfew extended to midnight, the streets are bright and buzzing. Portable generators, nearly impossible to find as they flew off the shelves in December, are being sold at half price.

The Kremlin’s campaign to break the Ukrainian will to fight by turning winter into a weapon and knocking out power ultimately failed — but there were moments when it seemed that all might be lost.

The darkest week in a long, cold season came in mid-November, when Russian missiles streaked in from three directions, bearing down on Ukrainian power plants.

Energy officials, gathered in a secret bunker in Kyiv, watched alarms flash on the large screens mapping the country’s energy grid as critical substations, thermal power plants and hydroelectric facilities all went dark. Then something happened they had never seen before over weeks of bombardment: All of the nation’s nuclear power plants were thrown into blackout.

Within seconds, control rods positioned above reactors at Ukraine’s three working plants dropped into cores to absorb neutrons and stop the chain reaction that could lead to a meltdown. The reactors, which provide 50 percent of the country’s energy, went offline.

At the same time, Russian missiles and drones severed Ukraine’s connection to the European grid, a critical source of energy that has helped Ukraine prevent collapse in its own grid.

On a continent of light, Ukraine was an island of darkness. Millions had no heat. Toilets did not flush. Lines formed at old wells as people lugged jugs of water to pitch-dark apartments in Kyiv. Internet service went down for many. Officials discussed mass evacuation plans.

“These were some of the most difficult days,” Ukraine’s energy minister, Herman Galushchenko, said in an interview.

Given the depth of the crisis — outlined in more than a dozen interviews with senior energy officials, utility workers, government officials and military intelligence — it is all the more remarkable that as winter has released its icy grip, Ukraine’s power grid not only survives but was even able, in early March, to produce surplus energy for the first time in months.

Major challenges to the power supply, however, may still loom.

Staving off the relentless bombardments has dramatically depleted Ukraine’s air defenses, newly leaked Pentagon documents show, and there is concern that Russian bombers may soon be able to prowl the skies of Ukraine’s cities unscathed.

But for now, rather than break Ukrainian spirit, the bombardments have only made Ukrainians more determined.

Some 97 percent of Ukrainians surveyed now say they believe they will win the war, and 74 percent predict that Ukraine will retain all the territory within the borders internationally recognized in 1991. The national survey released in March, was conducted by the National Rating Group, the largest independent research organization in Ukraine.

Still, there remains much work to be done. The Russian assaults destroyed or damaged more than 40 percent of the nation’s energy infrastructure, and it will cost billions of dollars to repair, according to a new report by the World Bank.

It was not just missiles.

In the towns and cities where Russian forces were forced to withdraw, infrastructure was deliberately destroyed as the invaders fled. They littered the ground with thousands of mines, making repair work slow and treacherous. And all along the front, ruined towns and villages were without power for months.

Since its sustained bombardment of infrastructure began in October, Russia hit 112 different targets with 255 missiles, Andriy Kostin, Ukraine’s prosecutor general, said in early March. Russia deployed hundreds more missiles and drones that were shot down.

Ukraine’s ability to survive the war on its grid was made possible by a combination of new air defense systems provided by Western allies, prewar planning to reduce a longstanding dependence on Russian energy, and deft problem solving by engineers.

The country was also helped by a robust grid — a legacy of the Soviet infrastructure design — international donations of critical supplies and the dedication of utility workers who often worked around the clock and under great risk. Dozens of energy workers have been killed in missile strikes and mine explosions, and hundreds more injured, Ukrainian officials say.

The first wave of missiles left Ukrainian power workers stunned.

“Everyone had big eyes,” said Ihor, the chief engineer at a critical substation.

But after two to three weeks, he said, the pattern of Russian airstrikes became clear, and utility workers learned measures to protect some of the most vital equipment.

“The next attacks were scary, but we already knew what to do,” Ihor said. “We felt much more confident.”

The New York Times was allowed to visit several substations that had come under repeated attack on the condition that it not reveal their locations or the full names of employees, for safety reasons.

At the heart of every power substation are hulking, high-power autotransformers. These are used to convert electricity from high voltage during transmission to low voltage for distribution to consumers.

Ukrainian officials suspect that Russian missileers, assisted by electrical engineers and detailed maps of the Ukrainian grid, knew precisely what to target. New transformers cost about $2 million and weigh hundreds of tons, and Russia destroyed dozens of them.

But Russia’s grid attacks also backfired somewhat, prompting Ukraine’s supporters to speed up delivery of the air defense systems that Kyiv had wanted since the first days of the war.

Since Ukraine obtained these systems, the damage inflicted by missile bombardments decreased dramatically, Volodymyr Kudrytskyi, the head of the Ukrainian national electric utility, Ukrenergo, said in an interview in March.

Ukraine, however, still has few defenses against ballistic missiles, and it was unable to shoot down six Russian Kinzhal hypersonic missiles in the last large-scale attack, on March 9.

Mr. Kudrytskyi said that engineers worked closely with the military to track incoming waves of missiles and drones and tried to prepare the grid to limit damage.

Without going into technical details for security reasons, he compared it to the balance of riding a bicycle. The system needs to always maintain stability between generation and consumption, and a fluctuation of as little as 1 percent can create a cascading events that ripple through the entire system and cause widespread outages.

Russia’s goal has been to tip the system off balance. Ukraine has found ways to make that much harder, in part by severing its connection to the Russian power grid and connecting to the European system.

Russian forces tried repeatedly to hit the lines from Europe to Ukraine, and two major attacks in November did briefly sever that connection. That was also when the nuclear power plants lost power.

But it was while visiting one of those plants a few months later that Mr. Galushchenko, the energy minister, became convinced Ukraine would weather the winter. Repair work that might have been expected to take 260 days of work, he found, had been completed in just 40.

For millions of Ukrainians, the battle over energy could be felt every time their lights went out.

“It was a crazy time,” said Julia Shpyg, the manager at the Electric Cinema amphitheater. “I woke up one day and had no power. I went to work, thinking there would be power here and it was also out. That is when I knew how bad it was.”

“Going to the movies is like a vacation, a few hours to forget about the war,” Ms. Shpyg said. Now that was being put in doubt.

But the theater, like many businesses, found a way to stay open, using generators to offer limited showings.

Now, it no longer needs the generators, and the only interruption audiences have to deal with are the near-daily air alarms, a reminder that Russia has not given up trying to batter Ukraine into submission.

“Hopefully, we will never have to go through another winter like the one we just lived through,” Ms. Shpyg said.

Anna Lukinova contributed reporting.