The main curse of any state-owned industry is political interference. Eskom was free of this from 1923 until 1994. Its brief was simple: to make sure that South Africa had enough electricity. It was very lightly regulated, much less so than private electricity utilities in the United States of America (USA). It was an autonomous organisation run by technocrats. Engineers were in charge and were appointed entirely on merit. Even under apartheid, there was no attempt to Afrikanerise Eskom's senior management. Eskom's greatest CEO was Ian McRae, an English-speaker. Eskom was entirely self-financing. There were no state subsidies for electricity.
In about 1969, after South Africa's economic growth rate had topped 6% in various years in the 1960s, electricity demand threatened to outstrip supply. In those years, growth in electricity demand was double economic growth. Near panic set in. Then Eskom made its best ever strategic decision: it decided to embark on a concerted programme of building huge coal stations of standardised design, each one having six identical units. The result was that vendors and contractors from all over the world tripped over themselves to give Eskom the best prices and conditions. The stations were built on time and on budget. They were funded via cheap debt and all the debt was timeously repaid. The taxpayer didn't have to pay a cent. By the end of the programme, Eskom had plentiful and very reliable electricity at probably the lowest prices in the world - lower than that from private utilities in other countries.