Kyiv residents should be prepared to leave the city if there is a total loss of power, Kyiv mayor has said.
In recent weeks millions of Ukrainians have intermittently been left without electricity and water, as Russian air strikes target vital infrastructure.
Rolling power cuts are also in place to avoid overloads and to allow for repairs.
Some 40% of Ukraine's energy system has been damaged or destroyed by Russian attacks on power plants and lines.
Another city official has warned that, in the case of a total blackout, water supply and sewage would also stop working.
In winter in Kyiv, the average temperature is below freezing and drops even further at night.
The authorities were stocking up on fuel, food and water. At least 1,000 heating shelters are being set up across the city where people will be able to get warm in an emergency.
Residents in Kyiv have said that they know that power could be lost and supplies could become scarce.
Dmytro, a 30-year-old father-of-two told the BBC he had already made plans to leave Kyiv in case things got worse. He has stocked up on fuel, bought generators and will move his family to his grandparents' home on the outskirts of Kyiv.
He said he began making the plans after "authorities announced that they were going to open heating points" two weeks ago.
Another resident, Anastasia, 36, said she would remain in the city even if power was lost.
"Our defenders sleep on the ground, so we will manage to stay in our apartment even without heating," she said.
However, the head of the Ukrainian regional administration blamed Russia for the power outage.
'Heavy losses' in Donetsk
Russia is suffering "heavy losses" as it carries out "fierce" attacks in Ukraine's eastern Donetsk region, President Zelensky has said in his nightly television address.
The Insider, a Russia-focused, independent media outlet, reported that in four days, 300 members of a brigade of Russian marines were killed, wounded, or missing in the Pavlivka area.
Posts on pro-Russian Telegram channels have been drawing attention to the brigade's reportedly dire situation.
Mr. Zelensky also warned that Ukraine believes Russia is "concentrating forces and means for
source(BBC)