The outage began just before 14:00 local time on Friday due to a transmission fault compounded by poor weather conditions in central Cuba, according to UNE. The country's entire electricity grid suffered a "total disconnection", the energy ministry said, leaving millions without power.
By late Friday evening, power had been restored to some priority areas in the capital Havana, including those near hospitals and water pumping stations. Felix Estrada, UNE's national load dispatch director, said protocols for a "gradual restoration" had been activated, with the process continuing into Saturday.
The blackout is at least the sixth partial or total collapse of the grid this year. Cuba relies heavily on fuel imports, and a tightening of US sanctions, including an oil blockade that took effect at the start of the year, has worsened chronic shortages of fuel, food and medicine. Hospitals are struggling to function normally, and schools and government offices have closed.
Residents expressed frustration and fatigue. "Lately, it's becoming a habit," Havana resident Frank Lorenzo told Reuters. "Before it happened less frequently — once a month… just yesterday we were 24 hours without electricity, they turned it on for just an hour and it went down again."
"It's one thing after another: no water, no gas for cooking, no electricity," 36-year-old schoolteacher Lidia Fernandez told AFP. "Honestly, I don't know how we haven't gone crazy."
Francisco Rodriguez, 78, said his home had already been without power for 28 hours on Friday, and he feared he would not have electricity "for several days".
The repeated blackouts have triggered rare public protests in Cuba, where unauthorised demonstrations are restricted. The government has blamed the crisis on the US embargo and the blockade, while critics point to systemic inefficiencies in the state-run energy sector.