Kyiv, Ukraine Yana and Serhii Lysenko were fast asleep, their four-year-old daughter in her bedroom down the hall, when they awoke at sunrise to a noise they didnt recognize the ominous buzz of an engine, like a motorcycle or lawnmower.

I will never forget this sound, said Yana, 31, who recalls leaping out of bed and rushing to the window to look outside. And there it was, right above us, right above our heads, flying.

From their perch on the 23rd floor of an apartment block in central Kyiv, they could see a drone swooping across the pink dawn sky, like a kite. Then, they heard an explosion and saw a black cloud left hanging in the air. Yana said she felt paralyzed, rooted to the spot.

The weapon, later identified by authorities as an Iranian Shahed-136, known as a kamikaze or suicide drone for the way it explodes on impact, was soon followed by several more. The couple watched in horror as the menacing triangular munitions darted past, careening and dive-bombing towards a thermal power plant just over a mile from their home, which provides electricity and heat for the capital.

Describing the attack on October 17 part of a wave of strikes that caused blackouts across the country Serhii, 42, said he and Yana are acutely aware of just how lucky their young family was. The volley of drones that they watched from their window hit a high-rise apartment building across the street from the power plant in Kyivs Shevchenkivskyi district, leaving four people dead, including a woman who was six months pregnant. She and her husband, who was also killed, were expecting their first child.

Starting in October, Russian forces began launching barrages of cruise and ballistic missiles, ground-to-air rockets and loitering munitions, laying waste to energy facilities and other infrastructure on a scale not seen since the start of the war a significant gear-change in an already grisly fight. The relentless assault on the power grid deprived millions across the country of electricity, heat, water and other essential services as temperatures dropped. It has also left at least 116 civilians dead and 393 injured, according to figures from the OHCHR.

Russias attacks violate international humanitarian law, which prohibits the targeting of civilians and civilian infrastructure, according to the UN. In a report released in December, Human Rights Watch (HRW) said that it appeared Moscows tactic was primarily designed to spread terror among the civilian population, in contravention of Additional Protocol I to the Geneva Conventions.

After not being able to win the war for months on end, the Kremlin devised this particularly cynical tactic, said Tanya Lokshina, HRWs associate director for Europe and Central Asia, who has researched Russias armed conflicts in Chechnya, Georgia and Syria. I don't think that this cynical weaponization of winter was something that we encountered earlier. It was rather about absolute lack of care for civilians, and indiscriminate strikes, but not specifically using the cold weather season as a war tactic. That is new.

Initially, Russian President Vladimir Putin framed the assault as payback for the October 8 blast that damaged the Kerch Strait bridge, a critical supply route and potent symbol of Moscows occupation of the Crimean peninsula. But over time, the Kremlin made clear that its strikes on Ukraines energy infrastructure were aimed at making life unsustainable, and intended to force Ukrainian President Volodymyr Zelensky to the negotiating table. In late November, the Kremlin denied that the strikes were targeted at civilians, but said that Kyiv could "end the suffering" by meeting Moscows demands. Meanwhile, Russian politicians and propagandists on state media praised the strikes for leaving civilians to live in dire conditions, with one parliamentarian suggesting that ordinary Ukrainians should freeze and rot.

Temperatures in Ukraine during the winter months typically range between 23 and 36 degrees Fahrenheit (-4.8 C and 2 C), and regularly plunge to -5 degrees Fahrenheit (-21.6 C). Though this winter has been milder than most, life has been brutal for those in towns and villages pummelled in the countrys east, parts of which havent had electricity for months.

By using terror and cold, the Russians want to break our spirit and unity. They believe that cold will become their most effective weapon of subjugation, so they are trying to destroy our power generation facilities. They are also trying to break up our national power grid by targeting substations so that even if there is power, it cannot be transferred from one part of the country to another, Yaroslav Demchenkov, Ukraines deputy energy minister, told CNN in late January.

Russia is trying to steal the light from our homes, but they will not be able to put out the light inside Ukrainians or break our will, he added.

Against all odds, Ukraine has managed to keep the grid from collapsing. The government introduced scheduled power outages in some cities and towns, disconnecting consumers for four-hour blocks three times a day to help conserve energy, while electrical engineering crews raced to make repairs.

During blackouts, doctors have carried out heart surgeries under headlamps, families have cooked meals on camping stoves in their apartments and students have done homework by battery-powered flashlights. Meanwhile, parents have taken their children to points of invincibility, tents equipped with generators, to get a hot cup of tea, charge phones and, according to one photograph that went viral, connect life-saving medical equipment.

CNN collected data from public sources, analyzed reports and official statements, interviewed energy officials and experts, human rights researchers and aid officials, and people living in Kyiv which was among the most prominent targets of Russias renewed offensive in October to get an impression of the impact and scale of Moscows assault on Ukraines energy grid. One year into the war, the power situation seems to be stabilizing.

In the capital, the hum of generators is the soundtrack to daily life. Cafes and restaurants are full, offering partial menus even during power cuts. Shelves in shops are stocked. On February 15, Kyivs Mayor Vitali Klitschko said there hadnt been any outages for days, and the city was gradually resuming electric transport services, like trolley buses and trams. Two days later, Herman Halushchenko, Ukraines energy minister, said that electricity generation across the country was enough to meet the demand.

This is welcome news for the Lysenkos, who, like most of the citys residents, have struggled with the uncertainty of waking up each morning, not knowing whether theyll be able to cook breakfast and log onto the internet, or have to rush downstairs to take shelter. The family doesnt have a generator after a few explosions, authorities rolled out a public information campaign on the dangers of using the devices indoors, though that hasnt stopped some from installing them on balconies and have gone to stay with friends on cold nights. They worry about how the stress has impacted their daughter Liza, who now draws pictures of Russian missiles before bedtime.

Nobody expected or could have thought that Russia would resort to such barbarism to turn winter against us and bring us back to some sort of stone age. And it could have worked, Serhii said. But we were able to survive.

In early 2022, as Russian forces amassed on the border and fears of war grew, engineers at Ukraines national electric utility, Ukrenergo, were preparing for a long-planned experiment disconnecting the countrys power supply from the Russian and Belarusian grids. As one of the last steps in a 2017 agreement with Europe aimed at Ukraine joining the European power grid in 2023, Ukraine had to prove that it could operate autonomously from its neighbors in isolation mode for three days.

The test was originally due to take place in mid-February, but Russia requested they push it to February 24. Very, very few people know about this, Mariia Tsaturian, a spokesperson for Ukrenergo, told CNN. We agreed, but we kept thinking in the back of our minds, that this might actually be when they would invade, because Ukraine would seem weak.

Their suspicions were right. Just a few hours after Ukraine unplugged, Russia launched its full-scale invasion.

Ukrenergo had prepared for that possibility, secretly relocating their main control room to an undisclosed location in the west, to keep engineers safe and the grid stable. As the country was thrown into chaos, energy officials in the companys Kyiv headquarters were busy trying to speed up the timetable for joining the European system. No one was going to be reunited with the power grids with the enemy, Tsaturian said.

Three days of powering solo stretched to three weeks, and on March 16, a year-and-a-half ahead of schedule, Ukraine hooked into the European power grid. It was an early signal that, rather than driving a wedge between Ukraine and the European Union (EU), Russias war was bringing the country closer to the bloc, accelerating its integration.

It made our system stronger. It made us more resilient to Russias attacks, Oleksandr Kharchenko, director of the Energy Industry Research Center (EIRC), a research and consulting company in Kyiv, and former adviser to Ukraines energy minister, told CNN. He pointed out that the successful emergency synchronization also allowed Ukraine to start trading power with the EU in June, bringing in much-needed revenue while also providing affordable electricity to Europe during a time when prices were sky high.

But that balancing act was thrown off kilter on October 10, when Russia fired more than 100 missiles and drones, leaving scores of civilians dead or injured, and damaging electricity facilities across the country, including the city of Kyiv. The attacks triggered blackouts in several regions, disrupting water supplies and telecommunications services.

Before then it was only some attacks, one or two missiles or shells per week, and most of them close to the front line there were very rare cases [of energy infrastructure being hit] around the country and without big damages. But from this moment, they shifted their strategy, Kharchenko said.

The scale of destruction at individual sites has been difficult to assess, in part because Ukraines Ministry of Energy has restricted the dissemination of information detailing damages.

Russia launched more than 1,350 rockets and drones at Ukraines energy infrastructure between early October and late January, according to Ukrainian energy think tank DiXi Group, citing official records from Ukraines Armed Forces.

The prosecutor generals office of Ukraine has documented 240 Russian attacks on the countrys energy facilities from the start of the full-scale invasion until the end of January. Another 15 attacks have targeted the power grid in February so far. Data collected by the office and shared with CNN shows there were strikes on infrastructure in 24 of Ukraines 27 administrative regions, with the majority carried out since October.

The attacks have almost certainly been aided by Russian energy specialists, who worked for years with their Ukrainian counterparts to regulate the post-Soviet energy system and know the inner workings of the grid intimately, Ukrainian energy experts and officials said. Moscows main targets have been substations key nodes that reduce the voltage of electricity so that it can be transferred through power lines to households and businesses and power plants.

In an investigation of attacks in October alone, the UK-based Centre for Information Resilience identified more than 30 attacks on energy facilities, verifying the locations with satellite imagery and reports on social media. CNN reviewed the data but was unable to verify individual cases. Nearly 60% of those were substations, located mostly in western and central Ukraine.

Oleksandr Kubrakov, the country's infrastructure minister, told CNN in early December that around 50% of Ukraines energy infrastructure has been damaged, some of it totally destroyed. According to Ukrenergo, there is not a single thermal or hydroelectric power plant that hasnt been hit. Fearing repeat attacks by Russia, Ukrainian energy companies and the government have kept the list of impacted facilities carefully guarded, so CNN is unable to confirm those claims.

The war has cut Ukraines ability to generate electricity in half, according to the Energy Ministry. The biggest loss came shortly after the invasion, when Russian forces seized control of Zaporizhzhia nuclear plant, the largest in Europe, which previously accounted for about 20% of the countrys power generation and is still under occupation.

There is a big question mark about how to recover this deficit. If Zaporizhzhia came back online, it would be able to balance the overall need, but there is no sign of that happening anytime soon. Kyiv is also looking into the possibility of importing electricity from the EU, but the costs would be much higher an expense that the countrys consumers cant bear.

Our strategy is to rebuild generation capacity to Ukraine, not only Zaporizhzhia, but also coal-fired power plants, gas-fired power plants, other nuclear power plants, to be able to provide electricity to increase the production domestically, said Artur Lorkowski, the director of the Vienna-based Energy Community, an international organization affiliated with the EU that has been coordinating efforts to direct spare parts and infrastructure assistance to Kyiv. But what is equally important to ensure is that this electricity could be smoothly distributed across the country and this is the biggest problem now.

To knit the grid back together will require a great deal of investment, Lorkowski said. At the request of the European Commission, the Energy Community set up the Ukraine Energy Support Fund to procure much-needed supplies. The fund, to which governments and companies have committed 156 million ($166 million), has delivered more than 1,000 tons of specialized equipment and spare parts to Ukraine (of about 4,600 tons the country has received in total). Ukraines Energy Ministry is constantly updating a list of tens of thousands of priority items: from high-voltage autotransformers, to circuit breakers, cables and switchers. The biggest single delivery so far? An autotransformer from Lithuania weighing 200 tons, to be transported by sea.

No one on the planet has experienced such a challenge a country of this size being at war and their energy sector being weaponized in the way that Russia is doing to Ukraine, Lorkowski said. But theyve proved that they can keep the system running despite all these atrocities and shellings. And this is for me the source of hope that it will continue until the end of this winter.

When Denise Brown, the UNs resident coordinator in Ukraine, took up her position overseeing the international humanitarian response in the country last summer, she had one priority: preparing for winter.

When I arrived in August, the winterization plans were the first thing I jumped into because my fear was, we'd get to the middle of winter and it would be minus 20, and I would get reports of people freezing to death and this was what kept me up at night, Brown told CNN in late January after visiting the city of Vovchansk, in the northeastern Kharkiv region, where she said it was minus 15 degrees Fahrenheit.

In their fight to make sure people dont die from the cold, Brown said the UN is calling communities up and down the front line, making sure theyre getting what they need. Humanitarian aid trucks are criss-crossing these areas, delivering warm clothes, heavy blankets and hygiene kits, and repairing windows and roofs. The goal is to get to the end of February, when it is expected to start warming up.

One of the UN convoys recently traveled to Siversk, a flattened town about 20 kilometers (12 miles) from Soledar, which was captured by Russian forces in January. Only about 1,000 residents remain, without any electricity or running water. Those who have stayed behind are usually the most vulnerable older people, people with disabilities and chronic conditions, who either cant leave their homes or dont want to.

The saving grace in some rural, remote towns is that people can still heat their homes with wood fires or gas, and get water from wells, according to humanitarian organizations and Ukrainian energy experts. In some ways, it is almost a bigger challenge dealing with power outages in cities, where most people live in buildings with centralized heating and water systems. Most people in Kyiv, including Brown, stockpile jugs of water, (previous strikes have left the citys entire population, an estimated 3 million people, without access). From my point of view, its much more difficult in the urban areas, the impact is greater, its harsher, Brown said.

In most high-rise apartment buildings in Kyiv, residents leave vital supplies some food, water and diapers in elevators in case of cuts. Most people CNN spoke with though couldnt remember the last time they had used the lift, worried about being trapped inside.

This is very illustrative of what you see across Ukraine. It's about cafes and restaurants sharing their generators, it's about the special kind of places where people can charge their phones being created at shopping centers, at gas stations, you name it, said Lokshina, the associate director at the human rights watchdog, HRW. Its about helping others, not only taking care of your own, and that's how people are surviving.

The most recent head of HRWs Moscow bureau, Lokshina has been working in exile from Tbilisi, Georgia, since Russias Ministry of Justice revoked the organizations registration in April, along with other foreign rights groups. In November, at the height of Russias attacks on energy infrastructure, she was carrying out research in the Kharkiv region. In towns and villages she visited that were recently de-occupied, people had been living with no electricity for months. They were most devastated by a lack of connectivity, she said, unable to get in touch with friends and relatives, to find out how they were and what was happening in the outside world.

When she returned to Kyiv, Lokshina was struck by how life carried on. Before an official meeting in the capital, she tried to get her nails done but was unable to get an appointment every salon she tried was booked until curfew. Despite the continuing attacks, despite the blackouts, which happen time and time again, despite the unpredictability of it. And the risk factors. People make a point out of doing their best to live a normal life, she said.

In their apartment in Kyiv, the Lysenkos said theyve started to adjust to this new normal. Yana and her husband, Serhii, bought a small gas cooker, to heat up food. Theyve learned the power schedule by heart, so they can plan around when theyll have electricity and heat. They also had the buildings engineers reconnect the elevator, so that it would work even if power was out in their apartment.

You dont need much for happiness. A peaceful sky above our heads and some small comforts: a warm house with lights and water. Thats it, Yana said. Our values have changed a lot. In fact, we have changed.