Power began to go 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 fix the problem.
US sanctions and a blockade of oil from Venezuela have deepened authoritarian Cuba's energy and economic crisis.
President Miguel Díaz-Canel stated a little over a week ago that the island nation had not received any oil deliveries for over three months.
On Saturday, aid shipments from 120 organizations began arriving in Cuba.
