Ukraine's electricity transmission system operator, Ukrenergo, reported a 20% power generation deficit on Sunday.

"Electricity producers supply almost 80% of demand, which is gradually increasing due to the cold weather. The consumption restriction regime is still in effect due to a capacity shortage, which now stands at around 20%," the company wrote on Telegram, adding that critical infrastructure accounts for only 10 percentage points of the 80%. The capacity deficit stood at 25% on Saturday.

Blackouts were back again in the Ukrainian capital due to an increased load on the grid, Kiev's administration said.

Read: Ukraine PM: Half of Ukraine's energy infrastructure out of order

Earlier this week, Ukrainian authorities said that the works to put the energy grid in Kiev back online were about to be completed.

Ukrainian Energy Minister German Galushchenko said on November 25 that Ukraine's energy grid sustained the most massive missile attack since the beginning of the conflict with Russia. 

Moreover, Ukrenergo revealed on November 14 that one of Ukraine's vital energy plants was severely damaged by Russian airstrikes.

It is worth noting that ever since Ukraine orchestrated an attack on the Crimean bridge on October 8, Moscow has been targeting Ukraine's vital military and energy infrastructure. 

Ukrainian President Volodymyr Zelensky said on November 1 that about 40% of Ukraine's energy infrastructure had been damaged as a result of these strikes, causing massive power outages.

On October 22, the Chief of Ukrainian national energy operator Ukrenergo said that energy consumption in many regions in Ukraine was reduced to up to 20% after Russian strikes on the power grids caused major damage to energy infrastructure.