Attacks on Ukraine’s nuclear power plants would be particularly serious, said Hrychenko, the analyst. Reactors in Kiev currently provide 60 percent of the country’s total power, and any missile strike on the energy infrastructure that supports those plants could put them out of business.

Last month, Ukraine incentive European Union for aid, fearing that Russia will soon follow its nuclear infrastructure. The country’s president, Volodymyr Zelenskyy, warned at the UN that such attacks could lead to “nuclear disaster”.

The nuclear problem is worse in part because Ukraine’s other fuel reserves are depleted. “The country’s gas supplies may not be enough to meet demand this winter,” said Aura Sabadus, an expert on Eastern European energy markets at consultancy ICIS, as Kiev is “uncertain” to meet its filling targets of gas storage.

The situation has been worsened this year by the absence of Western traders and companies, which have been “reluctant to inject gas into storage due to repeated Russian attacks and less attractive margins,” she added.

Another unpredictable factor is the weather itself. There is still no “clear signal” indicating how cold the coming months will be in the country, according to Carlo Buontempo, director of the EU’s Copernicus climate change service. However, he noted, a cold temperature is “plausible.”

In a worst-case scenario — with temperatures dropping below minus 10 degrees Celsius and Moscow shutting down Ukraine’s nuclear power plants — the country could face blackouts of up to 20 hours a day, Kharchenko said.