This winter will be the toughest in Ukraine’s history as an independent state as Russia targets power and water supplies, worsening the impact of the war, an energy boss has said.

But Maksym Timchenko told Sky News that Moscow will fail to turn out the lights for too long with its missile strikes because of his country’s ability to repair the damage quickly.

The chief executive of DTEK, the largest private Ukrainian energy firm, predicted that people will endure the next 125 days of wintertime “as brave Ukrainians” despite the threat of new Russian attacks against the energy grid.

“We will survive and we will win,” he said.

Workers from DTEK as well as Ukrenergo, the national electricity company, have mobilised – at great personal risk – to repair power stations, substations and other parts of the network that have been targeted by Russian airstrikes since October in a new energy frontline.

“This has the same importance for Ukrainian victories as the military frontline,” Mr Timchenko said.

Four of his employees have so far been killed on duty since Russia launched its full-scale war in February. Three died in rocket strikes and the fourth was killed by a mine.

“I’m so grateful to our people… who work in this industry,” he said. “These are real heroes and will stay in the history of Ukraine forever.”

With Russia thought already to have bombed more than a third of Ukraine’s energy system, the boss of DTEK predicted the coming months would be the harshest since at least 1991 when Ukraine gained its independence from the then Soviet Union.

“I can say with full confidence [it] will be the most difficult winter because we have never seen such destruction, such behaviour of our enemy, and we never lived under such conditions – constant rocket attacks and destruction and damage and explosions,” he said.

Equally, “I have full confidence that we will cope”.

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Mr Timchenko said all six of his company’s thermal power stations had been hit, some of them several times, but they were all back up and running.

“In this fight, you learn a lot: how to restore power supply; how to restore the system; what creative technical solutions can be found so that we bring back our power stations,” he said.

“I have a strong belief that there is no chance that a complete blackout can continue for a long time so that people cannot live.”

But he appealed to the international community for more electrical transformers to assist with efforts to reconnect the grid. “Today, equipment is more important than money for us.”

A major attack on 23 November knocked power out across much of the country for tens of millions of people. Even many homes in the capital Kyiv were without electricity and water for at least 48 hours – the worst impact of Russia’s new tactic so far.

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However, Mr Timchenko said despite the damage, it had been possible to retrieve power supplies. “Now we start this countdown of the winter season – 125 days – and trust me, we will get through these 125 days as brave Ukrainians,” he said.

In one home on the outskirts of Kyiv, a couple in their 70s said they would never give up no matter how long they must go without electricity and running water.

Liubov Sudakova and Volodymyr Sudakov are lucky because they have a log stove that keeps the house warm when the power is out. They have also stocked up on food – potatoes and other vegetables – grown in their garden.

“We just need the bombs to stop falling,” said Liubov. “When bombs were flying in the summer… I was in my garden and heard this ‘woosh’ and later boom. So that was scary.”