The Cuban Electric Union, which reports to the Ministry of Energy and Mines, announced a total blackout across the island on Saturday, without initially giving a cause for the outage.
The union later said the blackout was caused by an unexpected failure of a generating unit at the Nuevitas thermoelectric plant in Camagüey province.
"From that moment, a cascading effect occurred in the machines that were online," said a report from the Ministry of Energy and Mines, which activated "micro-islands" of generating units to provide power to vital centres, hospitals and water systems.
Authorities said they were working to restore power.
Power outages, whether nationwide or regional, have become relatively common in the last two years due to breakdowns in the aging infrastructure.
The breakdowns are compounded by daily blackouts of up to 12 hours caused by fuel shortages, which also destabilise the system.
The last nationwide blackout occurred on Monday. Saturday's outage was the second in the past week and the third in March.
The blackouts have a significant impact on the population, whose lives are disrupted by reduced work hours, lack of electricity for cooking, and food spoilage when refrigerators stop working, among many other consequences.
President Miguel Díaz-Canel has said the island has not received oil from foreign suppliers for three months.
Cuba produces barely 40 per cent of the fuel it needs to power its economy.
Cuba's aging grid has drastically eroded in recent years.
But the government has also blamed the outages on a US energy blockade after US President Donald Trump in January warned of tariffs on any country that sells or provides oil to Cuba.
The Trump administration is demanding Cuba release political prisoners and move toward political and economic liberalisation in return for a lifting of sanctions.
Trump also has raised the possibility of a "friendly takeover of Cuba".
with reuters
