LITTLETON, Colorado, May 8 (Reuters) - Clean energy sources generated the smallest amount of Germany's electricity in over a decade so far in 2025, dealing a blow to the energy transition momentum of Europe's largest economy.

Electricity generation from clean power sources totalled just under 80 terawatt hours (TWh) during the first four months of the year, according to data from energy think tank Ember.

That clean energy volume is down 16% from the same months in 2024 and is the lowest for that period since at least 2015.

To compensate for the drop in clean electricity supplies, German power firms were forced to lift fossil fuel power output by 10% from a year ago, and the share of fossil fuels in the German generation mix has climbed to its highest since 2018.

This resurgence in fossil generation has placed Germany's power system under heightened scrutiny, as the country has promoted itself as a regional energy transition leader and a major proponent of a cleaner European electricity system.

Given the reversal in Germany's energy transition momentum so far this year, any continued backsliding by such an influential economy could undermine regional commitments to energy transition efforts.

CLEAN CUTS

A 31% drop in electricity production from wind farms has been the chief driver behind the lower clean energy supplies in Germany so far this year.

Just 39 TWh of wind-powered electricity was produced from January to April, which was the lowest wind total for that period since 2017 despite wind generation capacity in Germany climbing by roughly 30% in the intervening years.

Low wind speeds at turbine level were the main culprit behind the wind woes this year, and resulted in wind power's share of Germany's electricity production mix dropping from 34% in January to April 2024 to 24% for those months this year.

MISSED PEAK

German utilities may need to expect even lower wind output in the months ahead.

Wind power supplies tend to peak during winter and spring when wind speeds are normally highest for the year, and undergo their annual doldrums over the summer when wind speeds drop.

As a result, and after already seeing a more than 30% drop in wind output through the opening four months of the year, German power suppliers must now prepare for further declines in wind generation through the coming summer.

Thankfully for utilities, solar farms hit their production peak over the northern hemisphere summer, and should supply power firms with a record volume of clean electricity during daylight hours over the coming months.

However, due to the complete halt in solar generation at night, the peak in monthly solar output will fall short of the volumes generated by wind farms during their peak output periods.

That will leave utilities needing to boost output from other energy sources to plug any resulting supply gaps.

FOSSIL FIX

So far in 2025, Germany's coal-fired plants have been the go-to source for on-demand power, and the primary source of electricity in the country.

The 40 TWh of electricity from coal-fired plants is 16% more than during the January to April period last year, and is the highest coal-fired total for those months since 2023.

Coal-fired emissions are up by a similar degree, amounting to nearly 42 million tons of carbon dioxide (CO2) compared to 36 million tons during January to April 2024.

High natural gas costs have curbed German natural gas-fired power generation so far this year, which dropped by around 9% during January to April from the same months a year ago.

However, German power firms may opt to raise gas-fired generation going forward as regional gas prices have dropped by around a third since peaking in February.

As natural gas plants emit less than half of the CO2 as coal plants per TWh of electricity, an expansion in gas-fired production could result in lower overall emissions as long as coal-fired generation is cut back.

But if German firms opt to expand both coal and gas-fired output in order to keep up with overall power demand, total power emissions will keep climbing and could further undermine Germany's status as a regional energy transition leader.