(Bloomberg) -- Warren Buffett, long under pressure from activists to detail how climate change affects his businesses, used part of his annual letter to shareholders to highlight how wind power generated by a Berkshire Hathaway Inc. utility shows the company is reducing its reliance on fossil fuels.

Buffett’s letter, with topics ranging from share repurchases to the makeup of corporate boards, detailed how Berkshire Hathaway Energy -- one of the “lead dogs” of Berkshire’s non-insurance businesses -- has been able to keep rates lower than its competitors in Iowa, partially because of its ability to generate electricity from wind.

“Of course, wind is intermittent, and our blades in Iowa turn only part of the time,” the billionaire investor said in the letter, released Saturday. “In certain periods, when the air is still, we look to our non-wind generating capacity to secure the electricity we need. At opposite times, we sell the excess power that wind provides us to other utilities,” which “supplants their need for a carbon resource -- coal, say, or natural gas.”

Companies are facing mounting pressure to detail their environmental impacts. Earlier this year, BlackRock Inc.’s Larry Fink said climate change is likely to upend global finance sooner than expected. It’s not the first time Buffett has cited the Iowa wind push: At Berkshire’s annual meeting last year, he brought it up when asked how his conglomerate scores on environmental, social and governance factors.

By next year, Berkshire plans to have achieved wind self-sufficiency in Iowa -- something that’s helped lure technology companies to the state. Three of the five largest Berkshire Hathaway Energy customers are now high-tech giants, Buffett said.

“I believe their decisions to site plants in Iowa were in part based upon BHE’s ability to deliver renewable, low-cost energy,” he said.

To contact the reporter on this story: Katherine Chiglinsky in New York at kchiglinsky@bloomberg.net

To contact the editors responsible for this story: Michael J. Moore at mmoore55@bloomberg.net, Daniel Taub

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