South Africa’s near fourfold increase in rooftop solar power generation capacity in the year to March has reduced revenue at the struggling national utility and municipalities that distribute electricity.

The surge in installation of solar panels on houses and business premises, a result of recurrent power outages, has cut Eskom Holdings SOC Ltd.’s sales by 2.3% and cost the Buffalo City Metropolitan Municipality, where more than 700,000 people live, 350 million rand ($18 million) in revenue, Pravin Gordhan, the public enterprises minister, said in response to a parliamentary question on Thursday,

By the end of August solar panels capable of generating 4,481 megawatts had been installed, 2,500 megawatts more than last year, he said, citing a measure that excludes solar panels that form part of commercial plants built by private companies to supply the national grid.