More consumers would be affected by Eskom's increased countrywide load shedding, the power company said on Wednesday.
"Eskom has increased its load shedding power outages on a rotational basis," the company said.
It was emphasised in a statement that the situation remained vulnerable even after the load-shedding period was over because of ongoing maintenance to various power stations.
"We urgently appeal to residents and business to assist us in reducing the load by conserving energy. If most South Africans switched off their geysers during the day until after the evening peak which ends at 9pm, we would see a dramatic reduction in load."
The capacity shortage was also partly due to the current wet weather spell that had resulted in an increased demand of power.
"This has led to an impact on the generation of electricity, as several generating units had to reduce capacity, due to coal handling problems related to wet coal."
The supplier said the summer period was scheduled for routine maintenance on generating plants and transmission, and distribution infrastructure.
During this period of maintenance a number of plants would be out of the system, and this created additional risk in terms of the reliability of supply.
"Eskom is managing the situation by using energy resources which include the use of Eskom's gas turbines and hydro stations, buying back power from large industrial customers and partnering with municipalities and co-generators.
"There has been a call to the public to cut back on consumption but the effect of this call has not yet been felt."
Businesses were requested to turn off all non-essential lighting and office equipment during the day and overnight. - Sapa