For Mrs. Merkel, the embrace of clean energy represents a transformation based on the politics of the ballot box. Just last year, her center-right coalition forced through an unpopular plan to extend the life of nuclear power plants, with the last to close in 2036. That action inflamed public opinion but the Fukushima disaster politicized it. The nuclear crisis is widely believed to have caused Mrs. Merkel’s party to lose control of the German state of Baden-Württemberg for the first time in 58 years, in a March election that became a referendum on energy policy.

By Monday, Mrs. Merkel said the country must “not let go the chance” to end its dependence on nuclear power.

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But her ambitious plan will not be easily achieved. The cost of plugging the gap left by the nuclear shutdown is likely to raise power costs, particularly for Germany’s globally competitive industrial sector, which consumes nearly half of the total electricity supply. Germany hopes to have renewable sources provide 35 percent of its electricity by 2020, up from about 13 percent today, and reach 80 percent by 2050. Its efforts will be watched closely, analysts said.

“If the government goes ahead with what it said it would do, then Germany will be a kind of laboratory for efforts worldwide to end nuclear power in an advanced economy,” said Mark Hibbs, a senior associate in the Nuclear Policy Program at the Carnegie Endowment for International Peace in Washington. “No other country in the world is taking those steps.”

Switzerland — a much smaller nation — decided this month to abandon plans to build new nuclear reactors and will phase out its existing plants when they reach the end of their normal lives. Other European countries are standing by their nuclear programs, including France, which has 58 nuclear plants and two under construction.

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The Netherlands, deeply committed to reducing greenhouse gas emissions, intends to build new nuclear plants along with developing more renewable energy sources. Britain has no plans to reduce its dependence on nuclear power.

Poland, which is eager to reduce its dependence on Russian gas and oil, is committed to pursuing a nuclear energy program, despite the expense, according to recent statements by Prime Minister Donald Tusk.

The government’s decision drew criticism and concern from some political and business leaders. The powerful Federal Association for German Industry, known as B.D.I., sent a letter on Monday morning to the chancellery, warning her about the consequences for German business.

“How will the international competitiveness of German industry be guaranteed?” Hans-Peter Keitel, B.D.I.’s president, wrote. “Industry last year accounted for two-thirds of Germany’s economic upswing.”

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The government said all of the details of the phase-out had not yet been decided.

If the government concludes that there are not sufficient alternative sources of energy to make up for the loss of nuclear power, three of the newest nuclear plants will be allowed to remain open until 2022.