Satellite images reveal the dark side of household solar power – South Africa’s green transition is only for a few

As winter approaches, memories of the past haunt South Africans in more ways than one. The country has experienced years of rolling blackouts, known locally as load shedding. During the worst periods of these power cuts in 2022 and 2023, South Africans who did not own solar photovoltaic systems or generators would go without electricity for up to 12 hours a day.

Due to the extent of the damaging power outages, solar power was adopted quickly in South Africa. For example, in 2020, smaller systems installed at homes or businesses made up just 38% of the country’s solar systems. At that time, 62% of solar systems were utility-scale solar power. (These included large solar farms that feed electricity directly into the national grid.) But by May 2024, the share of smaller solar power systems had shot up to 74%, far more than that of utility-scale photovoltaic systems.

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As a team of researchers specialising in mapping, geography, and renewable energy transitions, we noticed that satellite imagery showed that some parts of South Africa were still brightly lit at night, even during power cuts.

We wanted to find out if this was because these areas were exempt from power cuts or if it was because they’d switched to alternative power sources.

So we compared publicly available night-time satellite images of 300 suburbs with satellite images of South African rooftops taken during the day. We looked at the images for both day and night between 2016 – when there were almost no power cuts – and 2023, when power was cut for almost 79% of the year.

The satellite imagery revealed that night-time light declined by 20% over urban South Africa between 2016 and 2023. However, some suburbs remained curiously bright even when the power was out.

We overlaid the satellite images with national census maps and found that areas where predominantly Black residents lived darkened twice as much during this time as predominantly white suburbs.

There were virtually zero solar panels in impoverished areas, whereas wealthy suburbs were plush with rooftop solar systems.

This reflected the spatial divisions established under apartheid – that is, the geographic divisions established under South Africa’s former system of racial segregation, where people were forcibly separated into different areas based on race.

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