Electricity had also arrived in the country's westernmost Pinar del Rio province, the last to see power restored, just before dark on Sunday, officials said.
Friday's grid collapse marked the Caribbean island's fourth nationwide blackout since October.
Cuba's oil-fired power plants, already obsolete and struggling to keep the lights on, reached a full crisis last year as oil imports from Venezuela, Russia and Mexico dwindled.
Even before Friday´s grid collapse, many across the island had already been experiencing daily blackouts that reached 20 hours or more.
Though Cuba had made progress restoring electricity on Sunday, officials said they were generating just one-third of typical daily demand, leaving many residents still in the dark.
Schools in Pinar del Río, Artemisa and Mayabeque provinces in western Cuba would remain closed until Tuesday to assure adequate conditions for students, the education ministry said.
Cuba blames the country's mounting energy crisis on a Cold War-era US trade embargo and fresh restrictions from US President Donald Trump, who recently tightened sanctions on the communist-run government and vowed to restore a “tough” policy towards the long-time US foe.
The government is pushing to develop large solar farms with help from China in a bid to reduce dependence on antiquated oil-fired generation.
**Reuters**