South Africa had to make "urgent decisions" this year to ensure the security of energy supply in the next 20 years, Eskom chief officer for generation Brian Dames said on Monday.

Addressing a National Union of Mineworkers energy forum in Johannesburg, he said that the country would have to continue building new capacity, while also investing in other technologies than coal.

According to some plans Eskom had devised, nuclear should contribute about 14,4% of the country's electricity supply by 2028, with existing power generation units contributing 41% and new coal-fired power stations about 10,7%.

Dames further highlighted that power conservation could no longer be a choice in South Africa and that it should be mandatory.

Meanwhile, finance director Paul O'Flaherty emphasised that Eskom had to commit to completing the Medupi and Kusile coal-fired power stations, as well as the Ingula pumped-storage project.

He noted that it was important for Eskom to obtain the R190-billion funding shortfall it was still facing for the next seven years, as the power utility could not afford to become insolvent.

He added that to stop the construction of the Kusile power plant now would be a waste of money, in terms of what had already been committed on the project.

Also, while Eskom understood concerns from environmental groups around the $3,7-billion World Bank loan, O'Flaherty said that it was not helping the power utility, as it could impact on its credit ratings and subsequently its ability to raise capital.

Dames added that the World Bank loan would also support renewable energy and environmental protection, as some of the funds would go towards building the largest wind farm in South Africa and the largest concentrated solar power plant in the country.