An electricity-supply crisis is looming in South Africa that could make intermittent outages in the past few months seem trivial by comparison. Eskom, which supplies almost all the nation’s power, will lose more than a quarter of its current generating capacity over the next decade as it shuts ageing coal-fired plants. Replacing that output and adding capacity needed to meet rising demand will take years and cost more than R1 trillion, according to government estimates. The problem is likely to worsen exponentially after 2030 as more plants reach retirement age. While Eskom is building two new plants, Medupi and Kusile, they are running years behind schedule and billions of rand over budget, and won’t be enough to plug the supply gap. The utility has limited scope to invest in more projects because it isn’t making enough money to cover its operating costs and service its debt, which had ballooned to R419 billion at the end of its last financial year. The government has said it will look to private investors to help fund new plants and step up purchases of renewable energy from independent producers, which have added 3 876 megawatts of capacity to the national grid since 2011. H...