According to the study by the state-owned investment bank KfW, the planned realignment of Germany's power supply from nuclear to renewables will require "additional investment needs of around €250 billion by 2020."
KfW describes itself as one of the leading sources of finance in the energy sector, estimating that it financed 80 percent of new wind turbines installed in Germany last year, plus 40 percent of solar panels.
The bank also financed the insulation of buildings.
In the wake of the nuclear catastrophe in Fukushima, Japan, the German government has decided to shut down all of its nuclear reactors by the end of 2022.
At the same time, renewables are to account for 80 percent of total electricity generation by 2050, compared with 17 percent last year, the KfW study said.