Merkel's center-right ruling coalition ended months of division on Sunday by agreeing the country's 17 nuclear power plants should operate longer than planned, giving each reactor an average extension of about 12 years.
The deal, welcomed by utilities, came ahead of an energy plan due from the government this month, and addressed concerns in the coalition and industry over the fate of the plants, the last of which was due to shut by 2021.
"I am in good spirits that it would stand up against potential lawsuits," Merkel told a news conference on Monday. "We believe we can get this into law without (upper house) approval."
The German public strongly opposes building new nuclear power plants and there is a major protest planned for Sept. 18 against the plan to extend their operating lifespan. Nuclear power accounted for about 23 percent of the power generated in Germany in 2009, unchanged from 2008, according to information from energy industry association BDEW.
Nuclear power stations are the most profitable large-scale plants after building costs are paid off, as the fuel is cheaper than fossil fuels and utilities do not need carbon certificates.
More than half of Germans surveyed consistently oppose extending the reactors' lifespans, opinion polls show. They are against the extensions due to memories of the 1986 Chernobyl disaster, and concerns over nuclear security and waste storage.
To sweeten the deal, the government said it would raise some €30 billion ($38.62 billion) from utilities in the years ahead, which would be used to cut budget deficits and to expand renewable energy.
Some groups were skeptical of the plan, saying the nuclear lobby was powerful.
"The nuclear lobby has successfully put through its bold demands," Dietmar Schuetz, president of German renewable energy agency BEE, said in a statement.
