Grossman told Welt am Sonntag newspaper that RWE plants would reduce their CO2 emissions from 180 million tonnes to 140 million tonnes before the end of 2012.
This includes closing 16 of our oldest units," Grossman was quoted as saying. "We will make as much money with renewable energy as we do now."
The German government has set itself the goal that one-third of the country's energy should come from renewable sources by 2020.
"We'll succeed in getting a full supply with renewables only if we can store electricity because the wind does not always blow and the sun does not always shine," he said.
RWE, which employs 66,800 people, supplies electricity to 20 million customers and gas to 10 million.