After Japan's 2011 Fukushima nuclear accident, Chancellor Angela Merkel decided to phase out nuclear power by 2022, an about-turn that started with the immediate closure of the country's eight oldest plants.
Since then Germany has accelerated a boom in wind farms, solar power and biofuels, promoted by subsidies and legal reforms, with the goal of generating half of its electricity from renewables by 2030.
But the ambitious push is costly and has led to a hike in the price of electricity.
According to the weekly news magazine, which did not cite its sources, the European Union's Competition Commissioner, Joaquin Almunia, is particularly concerned about the fact that consumers have to help bear the cost through a tax surcharge.
"On Wednesday, the European Commission wants to open a procedure against Germany for this assistance," the magazine said, adding that Brussels would likely also insist that energy firms pay back millions of euros in aid received from the state.
The weekly said EU Energy Commissioner Guenther Oettinger last week questioned Germany's conformation with the 28-member bloc's competition rules on renewable energy development.
Among other things, he criticised Germany's policy of providing local wind energy producers with aid while foreign companies competing in the same market do not receive such assistance.