Ukrainians are experiencing their first large-scale statewide power outages as officials reduce supply.
The action is intended to enable energy providers to repair power plants damaged by Russian air attacks.
The president’s office told Ukrainians late on Wednesday to minimise electricity use from 7 am to 11 pm and prepare for temporary blackouts if this was not done.
No schedule was announced for the outages, but cities such as the capital, Kyiv, and Kharkiv announced curbs on the use of electric-powered public transport such as trolleybuses.
They also reduced the frequency of trains on the metro.
President Volodymyr Zelenskyy has said Russian air strikes damaged 30 percent of Ukraine’s power stations in just over a week.