Warren Buffett briefly lost track of how many billions of dollars his Berkshire Hathaway Inc. (BRK/A) is spending to build wind and solar power in the U.S. That didn’t stop him from vowing to double the outlay.

Describing the company’s increasing investment in renewable energy at the Edison Electric Institute’s annual convention in Las Vegas yesterday, Buffett had to rely on a deputy, Greg Abel, to remind him just how much they’d committed: $15 billion.

Without missing a beat, Buffett responded: “There’s another $15 billion ready to go, as far as I’m concerned.”

Such bold remarks are common for the Berkshire chairman and chief executive officer. He frequently talks about hunting for “elephant”-size acquisitions and making multibillion-dollar stock purchases.

Still, the comment speaks to the kinds of investments that are increasingly appealing to the billionaire now that his Omaha, Nebraska-based company is the fifth-largest in the world by market value. With dozens of units spinning off cash, Buffett has been allocating funds to regulated, capital-intensive businesses such as railroad BNSF and power companies.

“Buffett has always steered Berkshire toward the future,” said Lawrence Cunningham, a professor at George Washington University and author of the forthcoming book “Berkshire Beyond Buffett.” “Lately, that has meant intensifying the company’s focus on rudimentary, long-lasting businesses.”

‘Keep Moving’

While utilities don’t offer the returns of businesses that Buffett, 83, favored earlier in his career, he has said he likes the industry because it provides opportunities for reinvestment and further acquisitions. He bought control of an energy holding company in Iowa in 2000 and helped bankroll its expansion.

The unit, now called Berkshire Hathaway Energy, operates electric grids in the U.K., natural gas pipelines that stretch from the Great Lakes to Texas and electric utilities in states including Oregon and Nevada. Its renewable investments include wind farms in Iowa and Wyoming, as well as solar farms in California and Arizona.

Unlike other utility-holding companies, Berkshire Hathaway Energy retains all of its earnings. That probably will continue, Buffett said yesterday, estimating that the unit could reinvest about $30 billion into its business in the next decade.

“We’re going to keep doing that as far as the eye can see,” he said. “We’ll just keep moving.”

‘Strong Need’

Berkshire has been able to plow so much into renewable energy because it can use tax credits to offset profit at other businesses, Abel, the 52-year-old CEO of Berkshire Hathaway Energy, said yesterday. Units at Buffett’s company include auto insurer Geico, Dairy Queen, Shaw carpet and T-shirt maker Fruit of the Loom.

Investments in renewable energy will be needed as the U.S. seeks to reduce its reliance on fossil-fuel generation. Electric utilities face cuts of 30 percent in carbon dioxide emissions by 2030 compared with 2005, according to U.S. Environmental Protection Agency estimates of a proposed rule issued June 2.

“It’s encouraging that he wants to invest because as an industry we have a strong need for capital,” Nick Akins, CEO of American Electric Power Co., said of Buffett’s remarks on renewables.

AEP is a partner with Berkshire in Electric Transmission Texas, a joint venture that’s building and operating power lines carrying electricity from the state’s windy plains to cities.

While spending $30 billion on renewable-energy projects would have been unheard of two decades ago at Berkshire, Buffett is signaling that the returns are attractive, said Jeff Matthews, a shareholder and author of books about the company. The comment may turn out to be more than an off-hand remark.

“If he says it, he means it,” said Matthews. “The whole complexion of the company has changed.”