The drop in water levels at the country's Gibe 3 dam had led to a deficit of 476 megawatts, Seleshi told a news conference, more than a third of the country's electricity generation of 1,400 MW.
Ethiopia has also suspended electricity exports to neighbouring Djibouti and Sudan, which earns the country $180 million a year, the minister said.
Under the rationing programme, which runs until July, domestic consumers will face blackouts for several hours each day, while cement and steel firms will have to operate fewer shifts due to the cuts, Seleshi said.