Electricity supply will be extremely tight from April to July, Public Enterprises Minister Malusi Gigaba said in Johannesburg on Tuesday.
"As we are heading to winter, I would like to urge that electricity be used carefully," he said at a briefing by Eskom on the state of its system.
Improvement of Eskom's maintenance practices was moving in the right direction. "This will eventually ensure long-term security of reliable electricity supply."
He urged the country to continue supporting Eskom's efforts to "keep the lights on".
"No effort is insignificant in this regard."
Gigaba said Eskom chose summer to do its maintenance as demand for electricity was not as high as in winter.
"Summer is characterised by much flatter and lower demand profile, hence Eskom uses this opportunity to perform its maintenance."
He said the maintenance was necessary to improve and maintain the utility's performance levels. "Due to a decline in demand and reduced capacity, the system stays tight throughout the day in summer."
The pressure of managing a tight power system was also due to delays in the construction of new power stations.
Gigaba said Eskom and its customers had, so far, been able to avoid a system collapse when no further reserves were available. "Without the support of customers, Eskom would have struggled to fulfil its obligation and meet its mandate."
His department would be looking at ways to avoid disruptive power cuts.
He commended the support of big business, particularly when Eskom declared a state of emergency on Thursday.
Major industrial customers were urged to reduce electricity consumption by at least 10%.
Shopping centres and retail outlets were asked to switch off geysers and adjust air-conditioning to 23 degrees Celsius to help reduce demand.
Eskom's chief executive officer Brian Dames said voluntary contributions from commercial and residential sectors helped avoid power cuts during the emergency.
"Despite declaring emergencies, there has been no rotational load-shedding [blackouts] across the country because customers have responded voluntarily," Dames said. – Sapa