About those diesel generators
You say that "Even in comparatively well-organised South Africa, it seems that diesel generators are a common household accessory in the wealthier Johannesburg suburbs".
That only because people are fed up with the rolling brown-outs that are caused by ESKOM inefficiency. 90% of the South African neighbours buy 90% of their electricity from South Africa. Add to that the idiocy of letting ill-qualified engineers anywhere near the Koeberg Nuclear Power station, the idiocy of taking down 30% of South Africa's power generating capacity in spring (yes, it's almost summer there now), and the reliance on an aging power line from another country, you have disaster.
Namibia had a fantastic power generation resource in the Ruacana power station (and as a kid I had the privilege to visit it with my father), but after the bombing of the Calueque Dam in Angola, Ruacana stopped generating power, and the whole project has never been brought back online (a big shame).
Moçambique has Cahora Bassa, but thanks to an agreement signed between Portugal and South Africa at the time of its construction, Moçambique has to suffer the indignity of exporting ALL its power to South Africa, only to purchase it back for a significantly higher price.
Botswana has practically no power resources to speak of (one major coal-fueled generation station), so they also import nearly half of their power from South Africa.
Swaziland is also a net importer of power. Let's not even talk about Zimbabwe.
Lesotho thankfully uses its massive Highlands Water Project to generate power while providing South Africa with water, so they are practically the only neighbour NOT using South African power.
It is scary that a country like South Africa has rolling brown-outs because of idiots at the wheel. And no, I'm not being racist, I'm a realist.