Renewable energy accounted for 54.5 per cent of Germany's power consumption in the first six months of the year, down 2.7 percentage points from a year earlier, as slow wind speeds curbed generation, data showed on Tuesday.
Germany has boosted its green power capacity as it seeks to shift towards a "low-carbon" economy and hit a political goal for renewables to account for 80 per cent of consumption by 2030.
It also needs renewable generation to fill the gap after it halted its imports of Russian gas in response to the Ukraine war.
But Tuesday's data from utility association BDEW underlines the need for back-up power when weather conditions are unfavourable.
For now Germany still relies on coal and some gas to supplement renewables.
Between January and June 2024, the renewables share was 57.2 per cent, according to the data from BDEW and the Centre for Solar Energy and Hydrogen Research, or ZSW.
"The decline in electricity generation from wind energy in the first half of the year was primarily due to the historically exceptionally weak wind conditions in the first quarter of 2025," said a joint statement.
The preliminary figures showed onshore wind production by volume fell 18.3 per cent and offshore volumes by 17 per cent year-on-year in the first six months.
Hydropower volumes fell by 29 per cent due to declines in precipitation and too little snow melt left to fill rivers after a warm winter.
However, photovoltaic generation increased by 23 per cent.
National electricity usage fell 0.7 per cent to 258.6 terawatt hours in the period under review, while domestic production edged down 0.2 per cent to 251.2 TWh, with the balance accounted for by imports.
(Reporting by Vera Eckert, editing by Barbara Lewis)