UPDATE 3-Power cuts ripple across South Africa

(adds minister of public enterprises comment, paragraph 4)

By Michael Georgy

JOHANNESBURG Jan 18 (Reuters) - Power cuts rippled across South Africa on Thursday, blacking out parts of major cities and spurring warnings from the state utility Eskom that unexpected shortages could extend into next week.

The cuts, which Eskom attributed to power station maintenance and the shut down of one unit at the country's only nuclear power plant, caused outages stretching from Cape Town to Johannesburg.

South Africa's power woes have raised political temperatures in the past, with critics accusing the government of failing to address the energy crunch plaguing Africa's biggest economy as it gears up to host the Soccer World Cup in 2010.

Minister of Public Enterprises Alec Erwin was "confident that South Africa as a whole will not be plunged into darkness", said a statement from his office.

Eskom spokesman Fani Zulu said the company would try to ensure that a 2,000 megawatt shortage would not take a heavy toll on homes and appealed to the public to switch off non-essential electrical equipment.

"The situation is critical. We expect about two hours of shortages a day. We will tap reserve resources. Hopefully we will resolve the problem early next week," he said.

One unit was shut down in the Koeberg plant outside Cape Town -- Africa's only nuclear power station -- which has been beset by outages. Zulu said 900 megawatts of the facility's 1,800 had been cut. It supplies 50 percent of the electricity in the Western Cape, South Africa's tourist hub.

Eskom's managing director for transmission, Jacob Maroga, said earlier in a statement carried on the SAPA news agency that the shortage would amount to 4,600 megawatts out of a total national capacity of about 36,000.

SWITCH OFF AIR CONDITIONERS

Calls for residents to decrease power usage have been broadcast on radio stations, while several areas of Johannesburg and other cities reported that power cuts had begun.

"Residents, whose areas still have power, are requested to switch off their geysers, swimming pool pumps, air conditioners and all other equipment that uses electricity," said the Nelson Mandela Bay Municipality in Port Elizabeth in a statement.

At the court building in the town of Krugersdorp outside Johannesburg, lights went out in underground holding cells, delaying prisoners from being brought to trial. Power cuts were also reported in several neighbourhoods in Cape Town.

South Africa's Impala Platinum Holdings Ltd (Implats) (IMPJ.J), the world's second biggest platinum producer, said power cuts would probably lead it to lose at least a half day of output at its Rustenburg operation.

"We can probably pick that up over the course of the next weeks and months. It's not serious, unless it carries on for a week, then it will impact production," Bob Gilmour, investor relations manager, told Reuters.

The world's third largest gold producer, AngloGold Ashanti (ANGJ.J), said it was cutting its heavy power usage but had not yet seen any direct impact from the power cuts.

South Africa is one of many countries on the continent suffering from power deficits that business leaders say could keep foreign investors away.

Eskom has been under pressure to repair ageing infrastructure as a booming economy fuels demand for energy. (additional reporting by Eric Onstad)