Tom Murley, who runs two funds with more than $1 billion in renewable energy investments at HgCapital, a private equity firm based in London, takes a similar approach but closer to his home base.

His great enthusiasm at the moment is building wind farms in Sweden anchored by a large €180 million, or $235 million, array north of Stockholm called Havsnäs that opened in 2010. Mr. Murley likes Sweden because it has very windy sites that mean his wind turbines spin faster and more often than those elsewhere, producing more electricity to help pay off their construction costs.

He also likes Sweden’s low-subsidy regime, which is less tempting for a regulator to cut.

“The closer you are to the wholesale price of power, the less you are at risk,” he said. He is also investing in onshore wind projects in Ireland, where the operating environment resembles that of Sweden.

Mr. Murley avoids offshore wind, which requires huge subsidies to make economic sense. He is also veering away from solar projects at the moment for similar reasons. Spain, where he made a large earlier commitment to solar, has cut its subsidies, sharply reducing returns and leading to lawsuits from operators, including HgCapital.

The goal of the renewables business, Mr. Murley said, should be to be competitive eventually on costs with other energy sources and not to rely on subsidies. He also believes in building businesses like his clusters of Swedish wind farms that have the scale to engage a team of managers and the clout to cut better deals with suppliers. His organization tries to buy turbines and other equipment that are reliable rather than cheap and does not skimp on spending money on maintenance.

Renewable energy, he said, “should be run like any other manufacturing business; it is best to be a low-cost producer.”

Both approaches seem to be working. Enel Green Power, which is 68 percent owned by Enel, the big Italian utility, has seen returns through stock appreciation and dividend of about 26 percent over the past year. The stock price had plummeted earlier, along with that of many other renewables companies.