The South African Chamber of Commerce and Industry (SACCI) business confidence index dropped to 111.3 in March from 111.9 in February.
SACCI said in a statement that the lagged and knock-on effects of electricity constraints on the economy and business confidence were of major concern.
The outages are costing more that $50-million in lost output each day, according to estimates by the energy minister.
The government said it has taken note of the IMF team's findings.
"National Treasury is aware of most of the risks to economic growth and is working on mitigating measures to address these," the treasury said in a statement.
