Power began going out in buildings in Havana around 6:30 p.m. local time on Saturday, just before darkness fell across the country. Work is underway to restore power.
U.S. sanctions and a blockade on oil from Venezuela have deepened authoritarian Cuba's energy and economic crisis.
President Miguel Díaz-Canel said a little over a week ago that the island nation had not received any oil deliveries in more than three months.
On Saturday, aid shipments from 120 organizations began arriving in Cuba after an oil embargo from the United States deepened the crisis.
