"We're looking at the tax (on nuclear fuel) as a contribution to our goal of shoring up the budget," Merkel told reporters during a visit to Lingen nuclear power plant in the northwest of the country.
"In addition to that, we have to discuss how energy companies will contribute to the development of renewable energies," she added.
Her remarks were expected to cause further resentment among energy companies which have already called for the scrapping of the planned tax on nuclear energy production of €2.3 billion ($2.9 billion) per year. The controversial tax is to be discussed in cabinet on September 1.
Merkel and her centre-right government have been laying down plans to slow the phasing-out of nuclear power in Germany, reversing a deal struck by her Social Democratic predecessor Gerhard Schröder and the Greens.
Leaving aside the matter of the tax, her government says the country needs more time to develop sources of renewable energy before it dumps nuclear power.
Members of Merkel's Christian Democrats have also been urging energy companies to do more to fund renewable energy.